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VW B5 Passat TDIs This is a general discussion about B5 Passat(>98 (2004-2005 in North America)). Non TDI related postings will be moved or removed.

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Old April 5th, 2018, 12:29   #31
PickleRick
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Quote:
Originally Posted by oilhammer View Post
Just to be clear, just because I have not SEEN a failure mode of a BHW EGR cooler as you describe, doesn't mean it cannot happen. Every 3.2L diesel Transit's EGR cooler fails like. So many, Ford extended the warranty on them.

But, it is pretty easy to see... start the engine up cold, and the coolant bottle will right away start gurgling. There is also a combustion byproduct testing device (gas and diesel are different) that can be placed over the bottle to see if the source of the sudden extra pressure is from that, but that alone will not isolate an EGR cooler or head gasket.

Compression test won't tell you squat. The engine has PLENTY of compression, an allowable difference in percentage would easily eclipse the amount of combustion passing into the water jacket to build up pressure.

Pumping high pressure into each cylinder might, but again you'd need a LOT of pressure, well beyond what any normal shop air can provide.
Really? I would think cyl wash plus a head gasket leak would yield very noticeable differences between cylinders. My only experience with a bad diesel headgasket came from older direct injected kubota 4 cylinders. Knock on wood I've never needed reason to do a compression or leak down test on any of my BHWs.

As for leak down my shop compressor is capable of over 200 psi but the leak down tester i have (from kohler for gas engines) has a regulator on it in which you adjust the pressure down to get the gauge at a particular setting to start which is some 45 psi i believe. Because of diesel ring gaps many times being much larger what is unacceptable for gas motors is just fine for diesels. Not 100% sure of the diesel limitations for leak down % but i more or less just test all cylinders whether 2 or 8 and if all are about the same i call it good..if one or two reads 20% more leak down or 20 psi less compression than the others i know that something in there may need addressing .

What is considered good compression for one of these?
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Old April 5th, 2018, 12:36   #32
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25 to 31 bar, with a maximum difference between cylinders of 5 bar.

So, even 500 mbar would be enough to see bubbles and gurgles in a water bottle, but WELL within the 5 bar tolerance of cylinder deviation.

You do not have anything in your shop compressor that can make cranking compression levels of pressure in the cylinder. If there was a breach somewhere THAT bad, the coolant would be instantly blowing out the bottle like a geyser as soon as the engine started.... and it would STILL run perfectly fine.

And remember, cranking compression is nowhere near what combustion pressure is, so again, just because a cylinder seals up tight with as much shop air as you can ram in, doesn't mean when the engine is running a breach isn't being exploited.
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Old April 5th, 2018, 12:54   #33
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But, it is pretty easy to see... start the engine up cold, and the coolant bottle will right away start gurgling.
This happens exactly as you describe: the engine is stone cold and I hear the coolant gurgling right away!

Is this the last 'smoking gun' to blame the head gasket?

The nail in the coffin :-))))
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Old April 5th, 2018, 13:15   #34
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The exhaust pressure at idle in the EGR cooler is not much, but I would just to do EVERYTHING you can to rule out the EGR cooler, I would do this:

remove both EGR cooler pipes (the upper is easy, lower, not so much, but the lower is more important... because gravity).

Pressure test the cooling system, and see if any visible coolant comes out either end of the EGR cooler... you may get it to run forward to the easier-to-see forward connection if the back of the car is raised, but other wise it will just run to the lowest point, which would be the rear connection.

If nothing comes out anywhere, then it sounds like you need to take the head off.

If you can get some, you can use hose pinch pliers to pinch off BOTH hoses to and from the EGR cooler (there is no vent hose on the BHW's cooler), and start the engine and see if the gurgling happens right away as you stated. Cannot run the car like that, as that circuit of the cooling system (EGR cooler and heater core) has to be open to allow proper engine cooling. But you can run it for a few seconds to see if the gurgling is happening anyway. Just have to make sure the hoses are completely pinched shut.

Another method (which would be a pain) is to disconnect and bypass the cooler with some sort of tube, so the car's cooling system still circulates, and attach two long hoses to the cooler's nipples, and route them up a foot or so, then pour water down one until it comes up to the other at a level, then while holding them up, start the engine and see if any bubbles come out of those water filled hoses... that way you have totally isolated the cooler from the car.
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Old April 5th, 2018, 13:20   #35
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Quote:
Originally Posted by oilhammer View Post
The exhaust pressure at idle in the EGR cooler is not much, but I would just to do EVERYTHING you can to rule out the EGR cooler, I would do this:
remove both EGR cooler pipes (the upper is easy, lower, not so much, but the lower is more important... because gravity).
Pressure test the cooling system, and see if any visible coolant comes out either end of the EGR cooler... you may get it to run forward to the easier-to-see forward connection if the back of the car is raised, but other wise it will just run to the lowest point, which would be the rear connection.
If nothing comes out anywhere, then it sounds like you need to take the head off.
If you can get some, you can use hose pinch pliers to pinch off BOTH hoses to and from the EGR cooler (there is no vent hose on the BHW's cooler), and start the engine and see if the gurgling happens right away as you stated. Cannot run the car like that, as that circuit of the cooling system (EGR cooler and heater core) has to be open to allow proper engine cooling. But you can run it for a few seconds to see if the gurgling is happening anyway. Just have to make sure the hoses are completely pinched shut.
Another method (which would be a pain) is to disconnect and bypass the cooler with some sort of tube, so the car's cooling system still circulates, and attach two long hoses to the cooler's nipples, and route them up a foot or so, then pour water down one until it comes up to the other at a level, then while holding them up, start the engine and see if any bubbles come out of those water filled hoses... that way you have totally isolated the cooler from the car.
What an excellent post this is.
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Old April 5th, 2018, 13:34   #36
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Thanks... I should also add, that, on the test method with the two hoses full of water, you'd of course need the EGR pipes back on the engine so that exhaust pressure can be in there of course.
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Old April 5th, 2018, 19:37   #37
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Mr. OH, very appreciative of the test you propose on post # 34. It seems something I can do although I might have to come up with something to pressurize the coolant reservoir.
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Old April 6th, 2018, 04:05   #38
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Coolant pressure testers may be available somewhere at a parts store, maybe even for rent/loan, but you will need the late VAG specific adapter for the bottle. Most all the "kits" have them though.
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Old April 7th, 2018, 12:21   #39
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I did the test below today and it came negative (meaning there was no hiss sound). I realize it is not definitive but maybe there is a ray of hope.

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Compression test!!!
Quick test you can do yourself, wait for the car to cool down and release the pressure in the coolant system. Now wait over night so it cools completely. Start the car for 10-20 seconds and then shut it off. Now go open the coolant cap; if there is a hiss of pressure then you have combustion gases making their way into the coolant system. Failing this test is definitive. If it passes then it may mean it is something else but it does not mean it isn't the head gasket and further testing will be required.
I was quoted 1800.00 for a head gasket repair but I opted to do it myself and saved BIG time.
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Old April 7th, 2018, 12:33   #40
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Also I wanted to share this picture that shows some rust in the EGR pipe connection. Whether this is related or not to my coolant loss I do not know.

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Old June 13th, 2018, 15:14   #41
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Thumbs up Happy ending :-)

Coming back to make a 'full circle' and report back. My new TDI mechanic Brian in Denton (alphaseinor) suggested I try a new coolant Expansion Tank Cap for the coolant reservoir. I bought one from a local parts store (Bap-Geon) branded 'URO Parts' (like this one one). This was installed last mid-April. Then I went to him (early May) for my second timing belt change since I own the car (the first one was done by Robby when I bought the Passat used with ~ 120K miles six years ago). While at his shop he took his time to inspect the car and do a long term coolant pressure test. He also looked at my recent used oil analysis test results and inspected my EGR. He did found a small coolant leak from the o-ring of the coolant sensor and he replaced that. His conclusion was that I do not have a head gasket breach and/or EGR coolant leak. My observations since the coolant pressure cap R&R (two months past so far) is that I no longer get coolant sprayed through the overflow hole under the coolant reservoir and the coolant level has not changed by my periodical visual inspections.

Brian set the torsion at +1 (used to be somewhere in the range of -0.5 to -1) and he hopes that this will address my cold starting problems (not where I live but when we travel to colder places in the winter). We will see how the new torsion setting will impact (or not) fuel mileage.

All in all I am relieved that the 'head gasket drama' had a happy ending. Thank you very much Brian from Digi Sport Performance!!!
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