You’ve noticed the signs of major engine trouble… white smoke from your exhaust, losing coolant, or that dreaded milkshake-colored oil. Your mechanic mentioned it could be a blown head gasket or a cracked engine block.
Here’s the bad news: without dismantling the engine, there’s no reliable way to know which one you’re dealing with. Despite that, understanding the symptoms, causes, and repair options will help you make informed decisions going forward.
Common Symptoms of BOTH Issues
Since both problems affect similar areas of your engine, they often show the same warning signs. Here are the symptoms you might notice:
1) White Exhaust Smoke
If you see thick white smoke coming out of your exhaust, especially on startup or during acceleration, coolant is likely burning in your combustion chamber. This happens because either the head gasket has failed or a crack has formed, allowing coolant to seep into areas where fuel and air should be the only things present.
Unlike the blue smoke from burning oil, this smoke typically has a sweet smell to it. The thicker the smoke, the more coolant is being burned.
2) Engine Overheating
Because a compromised cooling system can’t maintain proper pressure, overheating is the result. With a blown head gasket or cracked block, coolant can escape the system or combustion gases can enter the cooling passages, creating air pockets that prevent proper cooling.
Your temperature gauge will likely begin creeping up during highway driving or sitting in traffic. Adding coolant provides temporary relief, but the problem quickly returns since the system can’t hold pressure.
3) Coolant Loss
Finding your coolant reservoir empty without any visible leaks underneath your car is a huge red flag. The cooling system is pressurized and sealed, so if coolant is disappearing, it’s finding another way out.
You may notice having to top off coolant a bit too frequently, or the low coolant warning light keeps coming on. The coolant has to go somewhere. It’s either burning in the combustion chamber, mixing with your oil, or escaping through a crack that only opens when the engine is hot and under pressure.
4) Oil-Coolant Mixture
Notice light brown or milky-colored oil when you check the dipstick? This means that coolant has mixed with your engine oil. Some call this “milkshake oil” because of its appearance.
This mixing happens when the barrier between the cooling system and lubrication system fails. The resulting mixture can’t properly lubricate your engine’s moving parts, potentially causing additional damage if you continue driving. You might also spot this mixture under your oil cap or in your coolant reservoir.
5) Poor Engine Performance
Your engine may run rough, misfire, or lack power. This happens because the combustion chamber is being contaminated with coolant, disrupting the normal air-fuel mixture needed for proper combustion.
In addition, combustion gases can escape through the damaged area instead of forcing the piston down, reducing power output. You might notice the engine running worse when it’s cold or feel a loss of power when accelerating.
Understanding Head Gaskets
The head gasket creates a critical seal between your engine block and cylinder head. Think of it as a complex metal sandwich that keeps several different systems separate – the combustion chamber, oil passages, and coolant channels. When this gasket fails, these systems can mix in ways they were never meant to.
What Causes Head Gasket Failure
Engine overheating is the #1 killer of head gaskets. When your engine gets too hot, the metal parts expand more than the gasket can handle. This warping breaks the gasket’s seal.
Other causes include age-related deterioration, improper installation after previous repairs, or using the wrong coolant which can erode the gasket material. Notably, head gasket failures have been particularly prevalent in Subaru vehicles, where certain model years experienced higher-than-average failure rates due to design and material choices.
Common Failure Points
Head gaskets typically fail between cylinders or between a cylinder and coolant passage. The location of the failure determines what symptoms you’ll notice first. A breach between cylinders reduces engine power, while a failure into a coolant passage often shows up as white exhaust smoke or coolant loss.
Repair Options and Costs
Replacing a head gasket is a labor-intensive job that requires dismantling the top portion of your engine. Though a new head gasket is likely under $100, professional head gasket replacement typically costs between $1,500 and $3,000, depending on your vehicle model and local labor rates.
Some may recommend chemical sealants as a temporary fix, but these rarely provide a long-term solution and could cause additional problems.
Understanding Cracked Engine Blocks
An engine block is the foundation of your engine – a solid piece of metal that houses the cylinders where combustion occurs. While they’re built to last, blocks can crack under certain conditions. Unlike a head gasket, a cracked block often means the end of your engine’s life.
Common Causes of Block Cracks
Severe overheating is the primary culprit behind cracked blocks. When the metal gets too hot, it can warp and crack, especially if cold coolant hits the hot surface.
Freezing damage is another major cause. If water in the cooling system freezes (because of an improper coolant mixture), it expands with enough force to split the block. Physical damage, manufacturing defects, or age-related metal fatigue can also lead to cracks.
Where Blocks Usually Crack
Most cracks occur in high-stress areas like between cylinders, around bolt holes, or near cooling passages. Some cracks might only appear when the engine is hot and under pressure, making them harder to spot during a cold inspection. Deep cracks that reach into cylinder walls or main bearing supports are particularly serious.
Repair Options and Costs
Modern repair shops rarely attempt to fix a cracked block. While welding, gluing, or pinning were occasionally used on cast-iron blocks in the past, these repairs often proved temporary and unreliable. Today, most professional mechanics will recommend replacing either the block or the entire engine.
If you though head gasket repair costs are high, brace yourself. The cost to replace an engine block typically ranges from $4,000 to $7,000 (or more).
This high cost comes from both parts and the extensive labor required as the engine usually needs to be completely removed from the vehicle. Your exact cost will vary based on your vehicle’s make, model, and year, as well as who does the work.
Given these high repair costs, many vehicle owners choose to either replace the entire car or find a used engine as an alternative (still not cheap). If your car is older or has high mileage, putting $4,000+ into repairs might not make financial sense.
Diagnosing the Problem
While you can’t definitively determine which problem you have without taking things apart, here are some steps that can help assess the severity of your situation:
Visual Inspection
Look for external coolant leaks, especially around the head gasket area. Check your oil and coolant for signs of mixing. Examine the engine block for visible cracks or weeping coolant, though remember that many cracks only show up when the engine is hot.
Professional Tests
A compression test can reveal whether pressure is leaking between cylinders. A cooling system pressure test might identify external leaks. Some shops use special dyes or gas analyzers to detect combustion gases in the cooling system. While these tests can confirm you have a problem, they usually can’t pinpoint exactly which one.
Making the Repair Decision
Since diagnosis requires disassembly, many shops start by removing the cylinder head to inspect the head gasket. If the head gasket looks okay, they’ll check for block cracks. This staged approach helps avoid unnecessary work if the problem turns out to be just the head gasket.
What to Do Next
If you’re facing either of these serious engine problems, here’s how to handle the situation:
Immediate Steps
Stop driving the vehicle if you notice severe overheating or significant oil-coolant mixing. Continuing to drive can turn a repairable problem into catastrophic engine failure. If you absolutely must drive to a repair shop, keep the trip short and watch your temperature gauge closely.
Get Multiple Opinions
Have at least two reputable shops assess your vehicle due to the costs involved. Two separate quotes can easily be $1,000 apart. Since repairs are expensive, you want to be confident in both the diagnosis and the shop’s ability to fix it. Ask about their warranty coverage and what happens if they find additional problems during the repair.
Evaluate Your Options
Consider your car’s age, mileage, and overall condition when deciding whether to repair it. Sometimes it makes more sense to replace the entire engine or even the vehicle. A blown head gasket in a well-maintained car might be worth fixing, while a cracked block in an older vehicle could mean it’s time to start car shopping.
- Car Making a Humming Noise While Driving? (7 Causes and Cost to Fix) - December 10, 2024
- 7 Reasons Your Steering Wheel Shakes (at Low and High Speeds) - December 9, 2024
- 7 Symptoms of a Bad Timing Chain Tensioner (And Replacement Cost) - December 4, 2024
Hello,
I have an ‘08 Dodge Charger 3.5L (6 cylinder). Recently my alternator went out. Well the very same day I was at the part store buying a replacement, on the way home that day….my car began revving up it sounded like the rpm’s were raising quite quickly but the car wasn’t going the speed it should have been with rpm’s that high. I got it home, replaced the alternator and turned the car on….now I hear the lifters knocking and there is a small puddle of engine oil on the top of my motor under the valves and head gasket etc. The car runs but is a lot louder because of this knocking noise. It hasn’t overheated and aside from the alternator, I have not had any other problems. I did see some oil spots on my driveway for several days leading
Up to the day the rpm problem happened…but a friend convinced me they were his since he had been parking his truck there many times. Now I’m thinking they were not from him, rather coming from my car. What is likely to be the issue? Do you think I can put some Bars Leaks Carbon Fiber Head Seal in and be ok? Thank you for any input.
Hi, i have peugeot 1.6e- HDi – Diesel 68 kW, start -stop system(2014.year, manual). After a run the coolant in expansion tank level dropped. When the working temperature is reached(90-93 degrees Celsius) and higher load on the expansion cap, overflow. In case when I open the expansion cap before overflow the liquid level returns. Oil is ok engine perfomance ok.What it is? Thank you for your answer.
I have a 1970 XKE Jajuar. After a run the coolant temperature is normal but I have positive pressure in the coolant system that causes loss of radiator fluid from the reservoir to come out of the overflow tube onto the ground. Thank you for your answer in advance.
Is the overflow reservoir past the full line? How much coolant is spilling onto the ground?
I have a 1997 Toyota RAV4 2.0 4 cylinder engine. It over heated. I let it cool down. I added water to the radiator and it pores out the driver’s side rear of the engine. It won’t hold water. I think it’s a blown head gasket. Could it be anything else?
Could just be a bad coolant hose or leaking freeze plug. You’ll have to take a look at the back of the engine to get a better idea.
Generally when you blow a head gasket you don’t hemorrhage coolant out the side of the engine (unless something even more serious happened). An external blown head gasket will leak, usually slowly, down the side of the engine. An internal head gasket leak creates white smoke and causes overheating.
I drive a 320d E90 it’s got a problem with the coolant. I need to put around 2 litres of water a day into it. There no smoke there’s no problem with performance. And no visible signs that it’s coming out. It is also burning oil however I have no had a chance to do an oil change. This problem was present when I bought the car (without realising) I had the car 7000 miles now
That’s a lot of water. My initial thought is an internal head gasket leak, where the oil and coolant are leaking into the combustion chamber. Have you noticed any excessive blue or white smoke coming from the exhaust?
I have an 03 Toyota. My car will not exceed 4000 rpm. Redline is 7k-8k. When I put the pedal on the floor, there is a short delay where the revs shoot up but vehicle speed hardly increases. They car will beep for a while when experiencing these issues. Also I think my engine coolant is darker than usual, but I haven’t noticed unusual engine temp. HELP!
Not sure, I would bring the vehicle to a mechanic to have that diagnosed. It may be an issue with the transmission since the engine speed is increasing disproportionately faster than the ground speed.
I have a 2006 vw jetta tdi , engine has a knocking sound and it has very low power when taking off , no overheating nor oil coolant mix . What could it be please , thank you !
Not sure. Can you tell where the knocking sound is coming from?
I have a corolla sport 2011, after some while it started missing coolant but all my mechanic can’t see the trace of the leak, they said i should change radiator and i did, after that, the car still ovetheat and the worst of it all it takes all the water into the reservior tank but never returns it back to the radiator and it will start bubbling once i drive around for like 20minutes, now the machanic said i should change the top gasket, please i need help and perfect suggestion
I don’t know that I can provide a perfect suggestion, but I would consider doing a leak down test to see if you can confirm that it is in fact a head gasket leak. If your car was overheating for a while, chances are you have a blown head gasket.
Hi,I have a Hyundai accent 1.6 its overheating,I replaced head gasket and thermostat but still the problem persists.it seems like the coolent is leaking somewhere but I can’t see any leak when checking around,what could be the problem
You could try a leak detector kit to see if you can pinpoint where it’s leaking from. If it’s an internal leak (inside the engine), a leak down test will help.
Hi i have a daewoo esparo and i took the head cylinder yo engeneering cos it was mixing water and oil for pressure testing bt they did not find a crack on it what could b a problem with my car cos is still mixing
2011 Chrysler 200 that had head gasket repaired about 10 months ago at the dealership. I am now told that the engine block is cracked. Could the repairman maybe be responsible for this?
It’s possible the vehicle was misdiagnosed the first time and the block was already cracked. Have they determined what caused the block to crack?
i have a 2000 ford taurus 86,000 miles and it recently started to slightly shake nothing major while at stop light and i also noticed very small amount of white smoke coming from tailpipe and small drips of water leaking from the exhaust not the exit of the exhaust but further back from it also my check engine light will flash a few times then stay solid its currently showing EVAP system leak detected and a cylinder 5 misfire
I don’t know, that’ll require some diagnostic work to find the root cause.
Hi, I have a 99 taurus with the 3.0 Vulcan that is non-running. (overheated and leaked coolant and would not start again after that). Trying to start it causes massive coolant overpressure, it would crank and coolant comes skyrocketing out of the coolant bottle. So I assumed headgaskets but now that I have them off they look ok. There is coolant everywhere though – in the manifolds, heads, block. Truly massive leakage wherever it’s coming from.
I thought I should take the cylinder heads to be pressure tested but now I’m wondering if it’s a cracked block if this would be a waste of time.
Any recommendations? I’m not a mechanic, this is my first time doing any work this involved.
Thanks in advance!
Kai
I have passat volkswagen 1.8 engine i bought second handed after a while it started to overheat.i changed top gasket,wash radiator and changed water pump but it still can’t stop.please can someone help tell me what else could be the cause of the overheating
Which gasket is the top gasket? You might want to do a leak down test to see if it is the head gasket. Start with simple stuff first like the radiator cap. Make sure you have enough coolant as well.
I have polo 2.0 it allows water in the coolant come out from exhaust. The engine is turning but misfiring. What exactly the the diagnostic problem
Could be a bad head gasket or intake manifold gasket leak. Might be best to take it to a mechanic for a diagnosis.
i have a 1973 ford truck with a year and a half old 390 motor that was using coolant but wasnt leaking now water is running out of exhaust on passenger side only but still runs but havnt driven it does that sound like a cracked block or head gasket
Hard to say without taking the head off.
The coolant disappears as fast as I pour it in, 2010 mini cooper no leaks on the ground, had a n oil change yesterday and the oil is already milky
That sounds like a textbook head gasket failure. You can probably do a leak down test to confirm. I would talk to a local mechanic as soon as you can to get the issue squared away.
If you let your car run about 30 minutes then turn it off. And check your oil cap and it’s milky but, you check your dip stick and it’s fine what could it be?
The oil cap should not be milky. It could be a head gasket failure, but you could probably do a leak down test to know for sure.
Is it possible to have oil in the antifreeze but no antifreeze in the oil for a blown head Or crack..Or would you say it could just be stop leak surfacing? But it’s been awhile since any stop leak has been used to just now be surfacing
Yes. Depending on where the head is leaking it’s possible to see one of those symptoms, but not the other.
I have a 2009 Infiniti M45 260k miles. I was told that my head gasket has a small leak. The car has never overheated, and no signs of oil and coolant mix. Symptoms are coolant slowly rising from the radiator at startup with the cap off. Also, I am having cooling parts fail one by one (radiator then water pump). The mechanic said it’s because of a small leaking head gasket that will keep finding weak points. The car is in immaculate condition. Can a head gasket blow without the car overheating?
While it’s true that a head gasket can leak without any overheating, I would still get a second opinion. If you let the car warm up without the radiator cap on, the coolant will naturally rise in any car, especially when the thermostat opens.
To know for sure if you have a head gasket leak, you can have a shop perform a leak down test. If air escapes the combustion chamber into the cooling system, you’ll know for sure that you have a head gasket leak.
So i have a 2013 Dodge Dart srt rallye 2.0l and the hose that connects to the actual thermostat is dripping pinkish. My coolant is orange. What would this be?
It’s probably coolant.
I have a inboard 302 in my boat and it filled the oil with water unit it started shooting milky oil out of the overflow by oil cap do you think it’s head gasket or block?
Do the chemical block sealers/gasket sealers really work? Is there a way to tell the difference between a blown gasket and a cracked block without taking the engine apart?
I am not aware of a way to tell the difference between a cracked block and a head gasket failure without a teardown of the top end of the engine. A leak down test would likely show leakage into the cooling system in either case.
I would use the recommended head gasket for your vehicle. I don’t know anything about block sealers but I would guess they don’t work as well as doing the proper head gasket repair.
I have a 2009 Lincoln mks 3.7 liter my fan coolant fuse had blown and I didn’t know it was a fuse . So I bought a new fan coolant assembly and my fan still didn’t come on and my car kept running hot so weeks later found out it was the fuse and replaced it and my car started running back properly until today it just started to jerk and when I checked it the coolant was leaving and running into my oil I checked the dip stick and it had a coffee look to it is that a blown head gasket
That depends, do you drink black coffee or Starbucks frappuccino? 🙂
If you’re worried about the possibility of head gasket failure, I would do a leak down test to see if any air is escaping into the cooling system. That will tell you for sure if the problem extends beyond the cooling fan fuse. Running the motor hot for prolonged periods of time does have the potential to ruin head gaskets, though.
Took my car to the garage after it had been stood for 6 years. They got it running again, and it passed the MOT. Within 10 minutes of picking it up, it was overheating. I put coolant in once it had cooled down and tried once more – solved; then I noticed the white smoke 🙁 A loss of coolant level, which I’d been topping up at the rate of 1L per 10 miles a day local journey. Suddenly, that has stopped happening, the coolant level stays as it should and the car stays colder than normal temp with no white smoke present. Initially, there was a central water drip, which also has now stopped happening. Instead, now, i’m getting a shuddering engine, and low-performance acceleration; you can feel a little bit of kickdown, but not much at all. The garage reckons its the head gasket, I’m more suspecting a cracked block. I don’t want the expense of engineering the block if its dead, that’s 500+ (estimate for gasket + labour + belts, more for a repair) pounds gone for no reason. any advice? I do have a spare engine, but it’s been stood over 10 years. Don’t know what to do for the best.
That’s a long time for a car to sit without running. Personally, I would do a bunch of testing to pinpoint the location of the coolant leak before going any further. Is it leaking from a hose and burning off the exhaust manifold? Is it being burnt in the combustion chamber and escaping from the tailpipe as white smoke? Check if you can see or smell any evidence of a coolant leak in different parts of the engine bay.
You could also perform a compression and leak down test. A leak down test will tell you more and often reveal the location of a leak in the combustion chamber on the compression stroke, when the chamber is supposed to be sealed.
A cracked block is typically more rare than a head gasket leak, and if the car sat for that long, I wouldn’t be surprised if it was the head gasket after all.
Opened the block and only one bolt has milk. Being a friends showcar, I’m wondern why
Hi. I have a jetta 5 tdi. In the antifreeze bottle are grey thick stuff floating. The oil cooler has been tested under high pressure and doesn’t leak. The pipes from the antifreeze bottle are clean inside. The oil dipstick are normal. The heat gauge is normal. The car performance is excellent. What can be the cause of the grey thick stuff in the antifreeze bottle? When you put your finger in the inside of the bottle and take it out it looks like oil.
I’m not really sure. It could be some old stop leak in the system, or some other random gunk that has floated to the surface from inside the cooling system. If the cooling system hasn’t been flushed in a while, I would go ahead and flush it to be on the safe side. Otherwise, just scoop out any chunks of the stuff you can reach, then top off the coolant back to the full level. If the car is otherwise performing well I wouldn’t worry about it too much.
i have a 85 JD farm tractor with a 3cyl. Yanmar 21 HP diesal. just recently was told i have low compression on 1 cyl. , was within operating range. Since noticed that after just a few minutes of idle or light use that i am seeing coolant dripping from overflow. after inspection i realize that my overflow water is black. obvious that exhaust in leaching into coolant & forcing coolant to back pressure out overflow. is this a sign of cracked head/ block or gasket. does not appear that water is in oil.? also did radiator pressure test and had slow/minimal loss.(not running). if that matters?
It sounds like you’re on the right track. I would suspect a head gasket leak in this case.
I have a Chevy tracker 2.o could a blown intake casket build presser in raider and make it over heat?
It shouldn’t build pressure in the radiator as long as the radiator cap is working. I don’t think the intake manifold gasket would cause an overheat for a Tracker, but I’m not certain on that. A bad intake manifold gasket should only cause overheating if there are water jackets in the intake manifold.
Have a 2013 v8 5.7L Durango. Performs perfectly and no over heating. But after driving highway speeds once parked will purge coolant out of the reservoir tank. And does not do it on the return trip or driving around town. Temp never goes above 228. No smoke from tail pipe but leak test showed positive for compression gases in coolant. Almost instant positive when doing the test. Could it be a leaky head that hasn’t blown yet? Or something else?
Yes, it is possible that this was caused by an internal head gasket leak.
I’ve seen this happen due to a bad coolant reservoir cap on a VW pressurize system vents through the cap. Bad cap a good one will rattle when you shake it.
I have to put antifreeze every few weeks bout4/5 weeks. If i forget about it, it completely empties, then my 15 Chevy Cruze overheats really bad. Once I put more antifreeze, its good until it all happens again. Ive been doing this for about a year now; i keep a bottle of orange antifreeze in my trunk. What does it sound like could be the problem?
It’s possible you have a simple coolant leak. Perform a radiator pressure test to ensure the cooling system holds the amount of pressure it was designed for. While under pressure, check for leaks on the ground and around the engine bay. You may even look in the engine bay and notice it spraying out from somewhere. This happened to me… three times, in fact.
If you can’t find a leak, this would be a textbook symptom for internal head gasket failure. Internal head gasket failure means the leak stayed within the engine or cooling system, so you probably wouldn’t any coolant on the ground in this case.
If you do have a failed head gasket, you will likely also see white smoke coming out of the exhaust even after the car has reached operating temperature.
I have a 2009 Pontiac torrent, and I keep having to put coolant in it every couple weeks, and it seems as if there’s no leak that can be found, and occasionally the light comes on that says oil compression is low turn off engine, and it’s burning oil now too, would that be a cracked head or a blown head gasket?
Could be. In your case I would start with a leak down test for more information.
I was told by a mechanic that my truck may have a blown head gasket or a crack in the block cause gas and coolant was mixing to gether. Is that po8
Trying to diagnose the engine of a classic car. We assumed it was a blown head gasket, took the heads off and sent them to a shop. The shop just called back saying there were cracks in the head. (We don’t yet know/haven’t had the opportunity to inspect the heads. The shop has been a bit dodgy and we have reason to suspect this may not be true.) If there are indeed cracks in the head, does that mean the block is also cracked? It’s a PRV V6 engine.
No, if one or both of the heads are cracked, that does not necessarily mean the block is also cracked.
Is it possible to have a cracked blocked but no crack in the cylinder heads?
Have coolant pouring out exhaust as fast as I can put it in
Yeah, don’t drive your car. Probably your head gasket.
How do i know if the water circulation on my car has stopped
Your car would be overheating.