The two main parts of any engine are its cylinder head and engine block. The block contains the pistons and cylinders, while the cylinder head contains the rocker arms and valves.
In between the block and cylinder head is the cylinder head gasket. This gasket serves as a seal for all the cylinders inside the block. The seal prevents coolant from leaking out of the cylinders and it also prevents oil from leaking into the cylinders and mixing with the coolant.
Most importantly, if there is ever a problem with the engine block or the cylinder head, the gasket will allow the mechanic to separate these two big pieces of the engine so that they can be individually repaired.
If you suspect you have a blown head gasket, it may actually be a cracked engine block, and vice versa. The symptoms of each can be similar.
3 Symptoms of a Blown Cylinder Head Gasket
A cylinder head gasket is bound to blow out after a while. This could cause the motor oil, fuel, and/or coolant to mix with each other in the internal combustion chamber.
Since the head gasket is meant to prevent the mixture of these fluids, a blown head gasket could cause this and the results can be catastrophic. Below are three of the most common signs that indicate you have a blown head gasket.
Related: The Dreaded Subaru Head Gasket Issue
1) Antifreeze & Oil Mixture
A blown cylinder head gasket can cause oil to mix with the antifreeze fluid. But the same can happen with a cracked engine block so another symptom must also be present.
2) Engine Overheating
If the coolant is leaked into the oil, then it won’t be able to do its job properly of cooling down the engine’s components. This will cause the engine to overheat. The smart thing to do if your car is overheating, is to simply pull off to the side of the road and not continue driving.
3) Poor Engine Performance
Once you have an overheated engine, it’s performance will diminish greatly. The biggest issue will be slow acceleration and engine stalling since you then likely have low engine compression as a result.
5 Symptoms of a Cracked Engine Block
The engine block is what houses and protects the cylinders of your engine. The case of the engine block is lubricated to prevent any overheating of the cylinders or components inside of it.
The top of the engine block is where the cylinder heads are located. It closes the cylinders from the topside and allows the combustion chamber to be formed. It’s fairly rare for the engine block to ever get cracked, but it has happened before.
Once it does, the engine will begin to have all kinds of problems and present some very bad symptoms. After all, if the engine block can no longer protect the internal components from excessive heat and cold, then the entire engine is literally toast.
Here are five common signs you can expect from a cracked engine block.
1) Oil & Antifreeze Mixture
Engine oil and antifreeze fluid can mix together if there is a serious crack in the engine block. The antifreeze fluid will be able to find its way through the crack and then circulate with the oil. This will spell major trouble for the engine.
As noted above, oil mixing with antifreeze can also indicate a blown head gasket so consider other symptoms as well.
2) Engine Smoke
A huge symptom of a cracked block is smoke coming out of the engine. If you let this go for too long, it will lead to other engine problems.
The smoke is due to emissions fumes leaking through the crack instead of the exhaust system and out the tailpipe. With this you will also likely experience a drastic loss of power when trying to accelerate.
3) Seeing a Crack in the Block
If you truly need to confirm that you have a crack in the engine block, then just perform a visual inspection of the block to see if it has a crack in it. Of course, it usually isn’t as simple as popping the hood open.
If you don’t have the mechanical experience, you can hire a mechanic to do this for you and to get a certain diagnosis.
4) Engine Overheating
The casing of the engine block helps keep the engine’s components cool and lubricated. If there is a crack in the block, the engine won’t have the proper cooling available which will lead to the engine overheating and eventually internal damage if driving continues.
5) Low Compression
The internal combustion process allows engine compression to take place. Since the combustion takes place in the engine block, any crack that forms on the block will result in reduced compression since air is escaping. Once that happens, the performance of the engine will diminish.
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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.