3.6 Coolant leak found

[4S50]

125k miles and the thermostat housing (plastic) cracked for some reason. I had it fixed at the dealer and had the drive belt replaced while they were there.

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[Lost1wing]

125k miles and the thermostat housing (plastic) cracked for some reason. I had it fixed at the dealer and had the drive belt replaced while they were there.

I have had several plastic cooling system parts fail recently. Most of these parts fail when trying to remove/ replace. I don't even attempt to save the plastic thermostat housing on the VW's I work on. I think I will have one on hand for the Gladiator when the time comes.

 

[4S50]

I still have a leak, very slow, but it is leaking. Blackstone detected coolant in the oil sample that I sent them, but I am not seeing any oil in the coolant (and it tested negative for combustion gas in the coolant) or indication of coolant in the oil. I do think that I am smelling coolant in the exhaust. Has anyone had a similar issue that can offer some insight?

 

[Viper501]

Head gasket failing?

 

[chorky]

I have had several plastic cooling system parts fail recently. Most of these parts fail when trying to remove/ replace. I don't even attempt to save the plastic thermostat housing on the VW's I work on. I think I will have one on hand for the Gladiator when the time comes.

This is the exact reason why I'm going to be fixing up my little TJ starting this summer. These newer vehicles are amazing. But man isn't that something like $2,500 bucks to repair at the dealer if it is out of warranty?

 

[AmosMoses]

That sounds like a head gasket leak if you can smell it coming out of your exhaust. Don't know how this could relate to the thermostat housing.

 

[ShadowsPapa]

I still have a leak, very slow, but it is leaking. Blackstone detected coolant in the oil sample that I sent them, but I am not seeing any oil in the coolant (and it tested negative for combustion gas in the coolant) or indication of coolant in the oil. I do think that I am smelling coolant in the exhaust. Has anyone had a similar issue that can offer some insight?

Head crack around the throat of a valve, say, intake, where coolant can be pulled in during the intake stroke, and end up being pushed out the exhaust, traces in the oil as per oil sample, but no oil getting into the coolant and no combustion gases in the cooling system because the intake valve being closed during combustion prevents it.
there are several ways a head can fail.
A cooling system pressure test will show at least if it's got a leak, no matter what or where that leak is - however, sometimes it's worse with the engine hot, sometimes it's worse with the engine cold.
In the days of cast heads - you'd do a "magnaflux" of the head to expose cracks - and they could be almost anywhere there was a coolant passage near.

 

[Charles 236]

The way that I check for a head gasket leak is to start with a cold (ambient temperature) engine. I put a cooling system pressure tester on the cooling system, but I don't pump it up, I leave it at 0. Then I put a leak down test gauge set on the suspect head. Start with a cylinder which shows a misfire, if possible. Then I put pressure on it and wait a while, usually 15 or 20 minutes. If a head gasket or cylinder head has failed, it will build pressure in the cooling system, which the cooling system pressure tester shows. If it doesn't build pressure in the cooling system with the engine cold, I start the engine and run it until it reaches operating temperature and repeat the test. I have used this method on many 3.6 engines, because as noted above, a block test doesn't always show combustion gases in the cooling system.

 

[ShadowsPapa]

The way that I check for a head gasket leak is to start with a cold (ambient temperature) engine. I put a cooling system pressure tester on the cooling system, but I don't pump it up, I leave it at 0. Then I put a leak down test gauge set on the suspect head. Start with a cylinder which shows a misfire, if possible. Then I put pressure on it and wait a while, usually 15 or 20 minutes. If a head gasket or cylinder head has failed, it will build pressure in the cooling system, which the cooling system pressure tester shows. If it doesn't build pressure in the cooling system with the engine cold, I start the engine and run it until it reaches operating temperature and repeat the test. I have used this method on many 3.6 engines, because as noted above, a block test doesn't always show combustion gases in the cooling system.

That's another great way because it may take higher pressures to force something through that crack or "problem area". (and a leak down test of a suspect cylinder is a good troubleshooting step anyway)

 

[4S50]

I borrowed the combustion gas check tool (and bought the fluid) and it did not show any combustion gas in the coolant, so this would rule out a headgasket or some other leak that is higher pressure than the coolant system, right? Or am I understanding this incorrectly?
Didn't the Toyota 22R engines of the 80's have a known issue with a crack in the exhaust valve seat that caused coolant to burn in the cylinder?

 

[Viper501]

I borrowed the combustion gas check tool (and bought the fluid) and it did not show any combustion gas in the coolant, so this would rule out a headgasket or some other leak that is higher pressure than the coolant system, right? Or am I understanding this incorrectly?
Didn't the Toyota 22R engines of the 80's have a known issue with a crack in the exhaust valve seat that caused coolant to burn in the cylinder?

I think that was what @ShadowsPapa was talking about in a prior response.

 

[4S50]

My local dealer diagnosed that coolant is getting into the cylinders. They say that in their experience it is likely microscopic cracks in the block that can not be repaired and the engine must be replaced. Sounds like Maximus Gladius’ experience. Anyone interested in a motor swap candidate?

 

[ShadowsPapa]

My local dealer diagnosed that coolant is getting into the cylinders. They say that in their experience it is likely microscopic cracks in the block that can not be repaired and the engine must be replaced. Sounds like Maximus Gladius’ experience. Anyone interested in a motor swap candidate?

Since dealerships rarely actually tear into the engine's lower end, I wonder how they came up with that, how they have experience with "microscopic cracks" (which is really what most cracks are anyway - thus, the need to magnaflux and use other tools to actually find cracks)
By saying "in their experience" they are saying they've seen a lot of it, and rarely ever see bad head gaskets or bad heads. That's really weird, IMO.
These blocks have liners, so they are suggesting something really weird.
Sounds like they prefer swapping engines instead of repairing. On the other hand, to tear one down and then find a bad block, there's that side of things, too.

 

[4S50]

Since dealerships rarely actually tear into the engine's lower end, I wonder how they came up with that, how they have experience with "microscopic cracks" (which is really what most cracks are anyway - thus, the need to magnaflux and use other tools to actually find cracks)
By saying "in their experience" they are saying they've seen a lot of it, and rarely ever see bad head gaskets or bad heads. That's really weird, IMO.
These blocks have liners, so they are suggesting something really weird.
Sounds like they prefer swapping engines instead of repairing. On the other hand, to tear one down and then find a bad block, there's that side of things, too.

I agree, you would think that cracks that were manufacturing defects would have showed up before now. I have done alot of trailer towing and while I have never overheated it, that engine has been working hard. A stretched head bolt or two allowing a headgasket leak does sound more plausible. It also does not spund like something they are interested in investigating further, just swap to fix.

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