How can I tell if I blew my head gasket?

[ObedaTJ]

Okay so I got the Jeep more than a month ago. Jeep Wrangler 4.0L 2000, with about 140k on it. Two weeks after I got it, it started to overheat on idle. My mechanic said it was the radiator, so we replaced that along with the fan clutch and thermostat. That seemed to solve the problem. It was good for two weeks. However yesterday the problem was back. Overheating at idle again. Drove it to the shop. Mechanic opened the radiator cap with no gloves and as it being hot and pressured, he let go and ran away causing it to spray coolant over my engine bay. Dumbass gets a hose and starts hosing down the engine bay to clean it, Jeep wouldn’t turn on after that. We cleaned the engine bay, properly and wiped it down and dried it with a vacuum and then it turned on. We added new coolant to the radiator, and it seems to be fine again however I am supposed to return tmrw to see if there is any leaks.

My question is, could my head gasket be blown? My uncle thinks it’s that and it’s been stressing me out. Any help is appreciated!

 

[jtf440]

If your oil is milky, then coolant has been mixing, which is only from a bad head gasket. If the coolant system is pressurized (excessive bubbling with radiator cap off) then it is a bad head gasket. If your engine has blue smoke with a burning oil smell, it either has bad blow by (low compression) or a blown head gasket.

 

[ac_]

Ok so I think I would be pissed that your mechanical told you to replace all of that stuff and it didn't fixed the issue in the first place. My first suggestion is find a new mechanic, this one is going to cost you too much, and doesn't seem to be liable for his mistakes which are amateur at best from the sounds of it.

To answer your question there is a couple of ways to tell.

First is your water in your radiator white, or have any greasy residue on under the cap? If so, oil can be getting into your water

Second is your oil too full? Remove your oil cap and look for white or greasy film under the cap. This means water could be getting into your oil

Note water and oil don't mix. This means that both will sort of mix while it is running but when it sits the water will sink to the bottom. Try pulling your oil drain plug and see what comes out. If water comes out, then you probably have a blown head gasket.

Now if none of those things above are the case, you are not out of the woods left. I still have another trick up my sleeve.

If you have a coolant pressure tester you can put it on your radiator and pump it up. It should stay pressurized. If you can leave it on for a while see if the pressure goes down. If it does it could be pushing water into the combustion chamber. You can also pull the spark plugs at this point and turn the motor over and see if it pushes water out of the holes.

Those are the tests I would do to check for a head gasket leak.
You asked!

Just in case I scared you, the 4.0's are pretty tough, and rarely have head gasket issues, not to say they don't fail, but I have 178K on mine, and still on the factory head gasket as far as I can tell.

Good luck!

 

[TimboSlice]

Isnt there a issue with some of the heads cracking internally and shooting coolant out the exhaust?

 

[05 Blue Unlimited]

It went for 2 weeks so, keep an eye on the fluids either oil is getting into water causing it's level to drop (will also make the coolant have an oil slick) or water is getting into the oil (it will be milky) or in some cases water will blow out of the tail pipe. But either way watch the fluids.

I think it unlikely, though possible, the gasket is blown.

 

[bromel]

You have a 2000, so I would be more concerned about a cracked head than a blown head gasket. Google the 0331 head if you aren't familiar with its notoriety. I'm the proud owner of a 2000 as well, so I'm always stressed out about my coolant levels.

Get a kit to test the oil for coolant contamination. Hopefully your problem is a hose, or perhaps a water pump, but understand that 2000s are known for cracked heads and you will have to monitor your coolant like a hawk going forward. Replacing the head isn't the end of the world, of course, but it's possible the PO sold you the Jeep knowing the head was cracked. Fingers crossed.

 

[ObedaTJ]

There is something leaking out of the exhaust but it’s been leaking since i got it. It doesn’t smell like coolant. The mechanic filled the radiator, with coolant all the way and it seems to have lost, however the Jeep still hasn’t overheated. The oil looks fine and not milky. I am supposed to return tmrw to see what the issue is, i’m really hoping it’s sometjing small as I’m in college and this is setting me back in funds. Thanks for all your help guys!

 

[bromel]

Water out the exhaust is normal in cold climates as it’s just condensation during startup, but it should go away after a few minutes.

How much coolant did you lose over those few weeks?

 

[ObedaTJ]

Water out the exhaust is normal in cold climates as it’s just condensation during startup, but it should go away after a few minutes.

How much coolant did you lose over those few weeks?

Yeah my dad says it’s normal too. I’m not sure how much coolant I lost. I never checked. Until it started overheating again, mechanic filled it to the top on thursday and this is how it inside the resivior now

 

[ac_]

So it is possible there is nothing wrong.

When you fill your cooling system, especially when you drain a lot of it replacing a radiator, you can get air in the system. What happens is you fill it and it seems full but the top of the of the motor has air, but your radiator fills up. Technically you are low on water. Your inept mechanic thinks your system is full but it is not and you go off and drive it. After a while your system overheats again because that air works out after your thermostat opens and now you are low and water, Then while it is hot your stupid mechanic opens the system and it blows even more water out.

This could all be normal to an inexperienced mechanic.

Try this fill it up with fluid cold then watch it while it idles with the cap off. Keep it just a bit low. High enough you can watch the water above the fins but below the very top. As it warms up the thermostat will open and you should see the water flowing and maybe drop some. Once the water starts flowing then fill it to the top and put the cap on it. Then fill the overflow to about the halfway point or wherever the fill line is.

Go drive it and see if it stays cool. Then the next day if it stays cool open the cap and top it off again if necessary shouldn't need much if any and top off the bottle if necessary.

 

[TimboSlice]

My vote is a cracked head. There are plenty of places that take the old ones in as a core and send you a re machined one with all new gaskets and such. Its really not much different than changing the head gasket. Just swapping a new head. This is very common on certain models. Go look and see what number is on your head. If it is 0331, id almost be certain your disappearing coolant is going into your exhaust. Otherwise, sounds silly but your line to your overflow may be leaking, or the overflow bottle has a crack.

 

[ObedaTJ]

My vote is a cracked head. There are plenty of places that take the old ones in as a core and send you a re machined one with all new gaskets and such. Its really not much different than changing the head gasket. Just swapping a new head. This is very common on certain models. Go look and see what number is on your head. If it is 0331, id almost be certain your disappearing coolant is going into your exhaust.

No coolant leaks from my exhaust though lol.

 

[ObedaTJ]

So it is possible there is nothing wrong.

When you fill your cooling system, especially when you drain a lot of it replacing a radiator, you can get air in the system. What happens is you fill it and it seems full but the top of the of the motor has air, but your radiator fills up. Technically you are low on water. Your inept mechanic thinks your system is full but it is not and you go off and drive it. After a while your system overheats again because that air works out after your thermostat opens and now you are low and water, Then while it is hot your stupid mechanic opens the system and it blows even more water out.

This could all be normal to an inexperienced mechanic.

Try this fill it up with fluid cold then watch it while it idles with the cap off. Keep it just a bit low. High enough you can watch the water above the fins but below the very top. As it warms up the thermostat will open and you should see the water flowing and maybe drop some. Once the water starts flowing then fill it to the top and put the cap on it. Then fill the overflow to about the halfway point or wherever the fill line is.

Go drive it and see if it stays cool. Then the next day if it stays cool open the cap and top it off again if necessary shouldn't need much if any and top off the bottle if necessary.

I really hope it’s just his mistake.

 

[ac_]

I really hope it’s just his mistake.

Keep us posted!

 

[TimboSlice]

No coolant leaks from my exhaust though lol.

It could be burning off or it is being trapped and burnt off. Get a pressure tester. Test the cooling system and check for leaks. If the gauge is going down with no visible leaks its your head. Also, check your head for 0331, read up on this. Its very very common. Its hard to smell coolant over exhaust. I had a friend with a Grand Cherokee with this issue. You could never tell by sight or smell. NOTE! remove valve cover when pressure testing system.

 

[TimboSlice]

Some visuals to maybe help

 

[59 wagon man]

i have always been taught then when refilling the coolant system you should put the heat on high temp and run the engine. maybe this is where the coolant has disappeared to if your not losing or burning it

 

[Squatch]

So, if he has a cracked head and coolant is entering into one or more of the cylinders, wouldn't the spark plugs on those cylinders be substantially cleaner, as they're, in essence, being steam-cleaned? I've seen that happen before. However, if he hasn't put a lot of miles on it since he actually started having the issue, it may not show up quite as clearly.

 

[Squatch]

They crack by the exhaust port, not the intake.

Oh, okay...I was unaware of that. That definitely makes a difference. Thanks for the information!

 

[Squatch]

Wait...but if coolant is entering into the cylinder, regardless of from where, wouldn't it still "steam clean" the plug? The coolant is literally being heated in the cylinder and passing over the plug on three of the four strokes (not on intake stroke). Or am I missing something?