blown head gasket thoughts/confirmation

Overheating under load - leaking head gasket?

2002 Jetta TDI, 365K miles, blown head gasket?
The car overheated in June for the first time ever in 365K miles (original owner) on a long uphill. EGR bypass at 100K. It had started to lose coolant very slowly and I could see leakage and crud coming from the water pump so I assumed that was the issue and parked the car until a few weeks ago. I did TB install #4 including the water pump with metal impeller and the hard coolant pipe o-ring and the coolant temp sensor were replaced. It still overheats under load (up long hills), the car had no or intermittent heat blowing out the vents and the water in the overflow boiled out. I flushed the heater core and the radiator, both clean and clear which leads me to suspect a blown head gasket. A leak-down test found no outright culprit that I had expected to find? Both fans test good, the new thermostat is opening and the metal impellers of the new WP do not spin on the shaft. I'm convinced that it's the head gasket and I'm ready to pull the head. What has me confused is the seemingly okay leak-down test but I found a thread in this forum that stated that it is possible for the leak-down test to not show an outright issue. There's no antifreeze in the oil. Also, There's no coolant flow into the overflow tank like it should have but none of the hoses are blocked. I assume that head gasket exhaust leaking into the coolant system could stop coolant flow because of the higher pressure from the exhaust? I have had a lot of white smoke only at start up for the past year or so. I think that I have covered everything. Am I missing anything before I pull the head???

Sounds like a water pump failure if there is no return flow to the reservoir.

I think you should do a little more testing before going any further. I recommend a pressure test to see if the coolant is going anywhere. Pressurize the coolant system and see if it holds the pressure. Blockage somewhere could contribute to the issue. If the reservoir is removed and system pressurized it should hold what you put in, air leaks faster than water and often you can hear it leak. Might not hear it leak in the head, however, you should hear it leak other places if it is, and leaking without hearing is internal leakage.

a) It is doing this with a brand new Geba Water Pump with metal impeller from the idparts TB kit.
b) As for a leak when I unscrew/open the overflow tank after it sits all night after running I get the pressure release. Does that not prove that since it's holding pressure that there's not a leak?

They make a test kit that can detect exhaust in your coolant.

I know my guru played hell trying to diagnose my coolant leak until it got bad enough that the white smoke gave it away.

I did not have overheating issues though and the pressure tests never really concluded anything.

Belome, where did your leak end up being?

Coolant should continually circulate through:

1. The expansion tank
2. EGR cooler
3. Heater core
4. Oil cooler

All those return coolant through the black metal pipe that enters the Water Pump housing just below the Injection Pump. That hot coolant bathes the T-stat constantly. Once the temp is high enough, the T-stat begins to open. It is a gradual process, both opening or closing. The engine's cooling system depends on that constant flow.

Coolant to the top of the Expansion Tank comes off a stainless steel nipple on the end of the head below/next to the vacuum pump. The hose does have a branch that feeds into one the larger hoses. But, there is no flow there unless the T-stat opens.

I agree, do some more testing before removing the head.

From what you describe I suspect you have exhaust gasses leaking into the coolant passages, but only under high load conditions. This will over-pressurize the cooling system, forcing the coolant out through the overflow, and then the engine will overheat.

Pressure testing at anywhere near normal pressures, like 15 PSI may very well reveal nothing.

Think how high the combustion chamber pressures are when driving up a hill. I guess it would be thousands of PSI? Under such conditions the head may lift slightly, allowing gasses to leak into places they shouldn't be. Under lower pressures there may be no leak at all.

It might be possible to tighten up the head bolts a little more, but that is risky. If one breaks then you're looking at removing the head. On the other hand, if tightening them more doesn't help, then the next step is to remove the head and replace the gasket anyway. If you did decide to tighten them a bit more, you could take a torque wrench and just keep increasing the torque setting a little bit, attempting to tighten all the bolts in the correct pattern until you get a bit of movement, then increase the torque setting a small amount, like 3 ft-lbs, and bring them all up to that torque. This way you'd know they're all even, and just a bit tighter than they were. Again, if a bolt snaps, you've got bigger problems, so do this at your own risk. It's something I would do, because I'd be prepared to remove the head anyway, and in fact I'd be doing it with the knowledge I might end up scrapping the whole car, but if this is a car you absolutely rely on, and failure is not an option, then you might want to consider just replacing the gasket, along with new head bolts, which is the proper thing to do.

The "proper" thing to do is to employ a straightedge several different directions on that head face.

You don't just replace a head gasket on a cooked head. You determine if it is still straight or not.

Don't worry, all comments and suggestions are welcome but I'm not going to over-torque the head bolts past specs. I'm versed in dealing with a warped head, I bought an 05' Mini Cooper R53 with a warped head in otherwise great condition two years ago at a very low price and did the work in my garage for $300 in parts and my own labor. I'm confused about not having heat or intermittent heat at best in the tdi when the engine is at 190 degrees f. It's as if it has no coolant flow but if you read my original post I don't know what I could have missed? Any methods or suggestions on proving coolant flow through the block at idle? I have no problem pulling the head and going from there but I still have this sinking feeling that I have missed something. I believe that I'm at the point that if I can prove that there is coolant flow that justifies pulling the head.

After the engine has cooled down fully, like in the morning after sitting overnight, try squeezing the coolant hoses and see if they are still pressurized.

That's another symptom of exhaust leaking into the cooling system.

I had an old diesel Mercedes that developed the same problem you seem to have. It was fine for driving around under light load, but under heavy load it would push all the coolant out of the cooling system. Temperature would read high on the gauge, but there'd be no heat from the vents. One of the symptoms was that the cooling system would stay pressurized, even when cold.

FWIW....after reading everything in this thread.....I would suspect that you do have a leaking head gasket and possibly a warped head.

Yes, I feel that I've pretty much covered everything and that I'll be pulling the head soon. I'll post my findings.

Probably just a gasket, I had similar symptoms in my Golf although I did have circulation in the overflow at idle. I put about 30k on mine before giving in and pulling the head. Now after changing the gasket, I love my Golf again.

dingels75 said:

Belome, where did your leak end up being?

Click to expand...

Sorry for the late reply, yes it was my headgasket.

I pulled the head today. I did not find an obvious failure of the gasket at all and using a straight edge and a feeler gauge I cannot find any warpage. Someone please tell me that it is possible to have a leaking head gasket pressurizing the coolant system and not be able to visually see the issue with the head gasket. Tell me your experiences.

Maybe a crack in the head or block letting pressure get into the coolant?

dingels75 said:

I pulled the head today. I did not find an obvious failure of the gasket at all and using a straight edge and a feeler gauge I cannot find any warpage. Someone please tell me that it is possible to have a leaking head gasket pressurizing the coolant system and not be able to visually see the issue with the head gasket. Tell me your experiences.

Click to expand...

Not in a TDI, but in my '88 Samurai I was pushing coolant out the surge tank like crazy, but it passed a coolant pressure test both cold and hot. Darn compression
Pulled the head and I couldn't find any evidence of exhaust to coolant, but since a new gasket hasn't done it once.

If it's measuring straight, wouldn't hurt to check protrusion, then slap a new gasket on it. Unless you want to send the head out to get measured just for peace of mind.

Mine only showed signs leaking because the block had slight erosion from driving it so long with the leak. Also to see that erosion I had to stone the head and the block. Both sides showed erosion but surprisingly the block showed much more than the aluminum head.

Could Manifold be plugged? How does egr look?

The intake manifold has remained clean and clear after the egr delete and catch-can install 250k ago. The intake was at least 50% blocked with carbon sludge caused by the hot egr exhaust gas mixing with the breather oil mist the first time I pulled it at the 100k mark. This is a great mod for these cars but you'll have to resolve the CEL that the MAF will throw.