Head gasket?

rocketscience

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Oct 31, 2013
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Olympia WA
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96 B4v Passat TDI Wagon
Howdy,

My 96 B4v is retaining pressure in the expansion tank when cold, the next day or two, with some pressure in the upper radiator hose. Its not a ton, but it gives a healthy hiss when I open the cap. When started cold I can see some tiny bubbles rising up into the tank. If I run it for a minute or so from cold and then take the cap off, the expansion tank is not pressurized. I just started losing coolant at a very slow rate, maybe a pint in the last 1000 miles. The coolant looks bright pink and there isn't any discernible coolant presence in the oil. I do get smoke on cold startup but didn't think that was out of the ordinary, its done that for quite a while and smells like it always has. It starts fine and runs great, usual mpgs. My heater also doesn't blow that hot anymore.

Does this sound like a head gasket problem? I'm not sure what else it would be, but I've read some cars retain pressure (Drivebiwire said its normal), or that the system can build pressure if it cools down at night. I can't really say that I've noticed it doing that before now. If it is a HG I'm guessing the leak may be small enough that a compression test might not show anything and I hear block testers on these are useless. Maybe I'll do a crackle test on the oil.

The car overheated a couple of times two years and probably 20k miles ago due to fan problems (PO had it wired directly to the fuse box with tiny gauge wires) but hasn't overheated at all since, driving hard over mountain passes etc. on a pretty regular basis, especially last summer. I've had intermittent coolant leak problems on the car and have replaced most of the hoses and seals, but it hasn't leaked any coolant in at least 10 or 12 months until now. I've had to have the hose clamps pretty tight, for example, the new replacement 3 hose F shaped setup down behind the water pump leaked from one of its legs, so I put on a screw down hose clamp next to the assembled one, so maybe its been running at slightly higher pressure? I've been assuming the current coolant loss was just another little leak, a clamp the needs to be tightened but haven't crawled under to look yet.


I have the time to fix it now, but I need to make the 1200 mile trip to Boise and back next month. If it is the HG I'd probably rather just fix it now than wait for it to get worse. The car has 355k miles but the PO put a rebuilt head on at around 290k (broken timing belt). I replaced the TB at 340K.

Thoughts?
 
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oilhammer

Certified Volkswagen Nut & Vendor
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Dec 11, 2001
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outside St Louis, MO
TDI
There are just too many to list....
Pressure tester, with the glow plugs removed, in case the coolant does push into a cylinder.

Head gasket is certainly a possibility, but more like what was (or wasn't) done to cause the failure in the first place. I suspect poor block surface conditioning.
 

Vince Waldon

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All my Jettas have pretty tight cooling systems at the moment and will often have a little residual pressure the next morning (I have to remember to release the pressure before checking coolant levels).

That said...if you car is starting to consume coolant and there's no visible leaks it's either heater core (and you'd likely smell it) or at the headgasket: block prep from the last repair per OH's post, warped head from overheating, HG itself.

All of this means if you do confirm you've got a breach at the head/block interface it will probably be worth checking deck and head straightness as opposed to just opening it up and throwing a new headgasket in.
 

rocketscience

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Oct 31, 2013
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Olympia WA
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96 B4v Passat TDI Wagon
Right, I was definitely going to check the head for any warpage. Y'all basically just mean that they might not have cleaned up the deck surface well enough? Or that there might be scour marks on it so it isn't smooth enough?

So if I find an external leak and am no longer losing coolant, and I can pressure test it and it holds, then one would assume the head to block seal is okay and there is residual pressure just from design or temperature change. But if I can't find an external leak, pressurize it and it leaks down it pretty much has to be the HG. Not noticing any coolant smell in the cab or any coolant steam using the heater, so I don't think its the heater core, though it may need to be flushed. Is it possible for a leak to be small enough that the 450+ psi from the cylinders could push air through but 15-20 psi on the cooling system wouldn't, so a coolant pressure test wouldn't show any leak down but it'd still be leaking while running? Just thinking about hypotheticals before I test it.

Thanks for the replies guys.
 
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turbodieseldyke

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Free Mustache Rides
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98 jetta
Probably, if you have an external leak, it's because of the head-created pressure, and it's seeking the weakest point to escape from. You might fix the one leak now, only to have another spring up later (or in the same place).

Your conditions sound like most HG problems documented on this forum. And most of the time, none of those confirmed the HG is bad. But after replacing the gasket, the problem went away for most of us.


My pressure came back a year later, but I don't recall reading that from anyone else. Adding another 1/4-turn to the head bolts, at one point, did seem to help, but it's gotten worse since then. Since these are stretch bolts, I don't know what the end torque is supposed to be, so I can't really adjust them on that measure. I sure as hell don't want to break one off.
 

rocketscience

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96 B4v Passat TDI Wagon
Yeah, that's what I figured. I feel lucky that it didn't get worse two years ago, before I had more experience working on this car. It does seem to be getting worse now, and like I said, I'd hate to wait and have it do damage. I take a lot of long road trips. I think I'll just do the job, and soon. Consensus is to get a new TB tensioner if you need to take the belt off, right?

Thanks for the insight!
 

Ol'Rattler

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Good luck on your issue.

Could be worse I guess. My GD's Equinox had a common problem for Equinox's were it would leak all the coolant in the engine in a day. I'm pretty sure the coolant was going out of the exhaust. Nothing on the ground and nothing in the oil.

I breathed a sigh of relief when she wrecked that miserable car. Thankfully she wasn't injured.
 
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00013cave

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island state of Montreal
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1998 jetta TDI, 1997 GLX TDI
All my Jettas have pretty tight cooling systems at the moment and will often have a little residual pressure the next morning (I have to remember to release the pressure before checking coolant levels).

That said...if you car is starting to consume coolant and there's no visible leaks it's either heater core (and you'd likely smell it) or at the headgasket: block prep from the last repair per OH's post, warped head from overheating, HG itself.

All of this means if you do confirm you've got a breach at the head/block interface it will probably be worth checking deck and head straightness as opposed to just opening it up and throwing a new headgasket in.
Vince as I have read many of your posts over a few diesel sites believe me this is no dis,and respect much of you say. But the only time I have ever seen pressure in a tank after sitting overnight is when there is a bad head gasket or related problem. As far as I'm concerned pressure should bleed off by itself after a few hours. I don't see how a system can keep pressure for so long after expansion is reduced (heat)etc. As an example, on my AHU I had to pull the head after sucking in water in a big rainfall and replaced 2 con rods. I didn't have help putting the head back on and scratched the corner of the HD. Within a few weeks, I started loosing coolant from various places( weakest link and all). When I saw that after fixing all those leaks, I would have pressure in the tank the next day. Pulled the head, replaced the HG and problem solved. I drove the car this afternoon and if I went now to check there would not be pressure
 

Vince Waldon

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Hey... no worries...everyone has their own perspective. In my case, if a bit of residual pressure means a bad head gasket all three of my cars have bad head gaskets. :)

Kidding aside... I'm not talking about a good-sized hiss.. just a little wisp, and only if the car was driven the night before.

So we're probably on the same page, as is often the case. :) :)
 

rocketscience

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96 B4v Passat TDI Wagon
That's an important distinction and exactly why I started this thread. As I've been experiencing a healthy hiss a couple days later I think I've crossed 'the line' into a problem that actually needs to be dealt with. I'd been trying to research past threads without getting a definite answer and this thread has been very clarifying, thanks y'all! I'll update when I do the work and let you know how it goes and if the issue is resolved.
 

Yblocker

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Oakland, CA
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1997 Passat
I can add another case of residual cooling system pressure cause by a failed HG. I wound up replacing it using ARP studs. That cured it. The studs are re-useable too.
 

rocketscience

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I looked into the ARP studs, but they're way out of my budget, that would pretty much double the cost of the whole job. I think if I make sure everything is flat and cleaned up I'll be in good shape.
 

ToddA1

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Bringing up a good point about studs. Some people have had good luck pulling one bolt at a time and installing studs (one at a time).

-Todd
 

rocketscience

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96 B4v Passat TDI Wagon
So, I have everything collected and am ready to remove the head but I've been wondering if this would be a good time to re-ring the pistons. The car uses oil, a pretty large amount, about 1 qt/1000 miles and has the whole time that I've owned it, about 50k miles. I've just ignored it and been vigilant with checking the level, but I'd really like to at least reduce it. The low end has 360k and I've read that a lot of these are still in great shape at that age, but I'm wondering if my oil control rings aren't doing their job

More background info:

The car has a couple leaks but never leaves any spots on the ground.

I've checked the turbo shaft and it doesn't seem to have too much play side to side, zero play in and out. There isn't any oil on the tail pipe. The CCV is sucking a decent amount of oil but I don't think its anything out of the ordinary, the intercooler had about a half a cup in it and its probably been 15k since I've checked it, maybe more.

If I loosen the oil cap while its running it just kind of wobbles there, so the blow-by doesn't seem too excessive, which probably just means the compression rings are good and maybe aided by seeping oil.

It starts right up but smokes a little on start up, which I know is totally normal. I keep meaning to check after its sat a shorter period of time but keep forgetting. There have been a couple instances in the past where I've been driving downhill on a cold motor in gear and its taken a couple minutes for it to stop smoking. Smoke looks white.

The glow plugs are sooty but don't seem oily, unless that soot is just burned oil. At least the 3 I could remove. The second one barely turns and I'm afraid to mess with it until I commit to parking the car for a few days. I really hope it isn't cross threaded, but it looks like there is some brown residue in the depression around that plug and none of the others. I'm going to check for bubbling around it. I really just don't want to mess with it, but i guess with the head off i should take care of it. If I can get it out in one piece and the threads aren't buggered would chasing the threads be good enough of a solution?


The previous owner supposedly put a new or rebuilt head on about 70k miles ago, so it should be in good shape. The last time i had an emissions test the tech was stunned at how low the readings were. I will probably still change the valve seals.


I've also considered running BG109 for a couple of consecutive oil changes, but the cost/effort of just doing the rings when the head is already off is about the same. Any thoughts on this? I'd like to order parts tomorrow and get rolling on it ASAP if I decide to do this.
 
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rocketscience

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96 B4v Passat TDI Wagon
Anybody have any thoughts on this? I bought parts but can always return em, I'll definitely check the bore wear before proceeding.
 

ToddA1

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'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
Personally, I think you're opening a can of worms. While I'm doing this, I may as well do that....

How long are you planning on keeping this car?

-Todd
 

rocketscience

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Olympia WA
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96 B4v Passat TDI Wagon
For sure, I'm pretty aware of that and don't want to slide down the slippery slope... it'd be a real shame to do more work and not have any effect, or worse, have a negative effect. But I'd also like to keep the car for as long as I can keep it running, within reason. Honestly if it was ever hit or wrecked I'd probably try to put the motor in something else.
 

Vince Waldon

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Anybody have any thoughts on this?
I personally think the time to ask this question is once you get the head off and can examine and measure the bores.

Once you know the wear you can decide how many miles left before a rebuild is required, or if a light hone now is all it needs, or... :)

Any sort of ridge at the top will also be a big clue.
 

rocketscience

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Thanks for the replies, that's kind of what I've been thinking to, if there's a ridge or too much wear or vertical scratching a ring job wouldn't be any good, and I'm not ready for more drastic measures financially or time wise at this point. I ordered everything I'd need to do rings so that if I decide to go that route I won't have a bunch of down time. Are there any other clues I can use when visually examining the cylinders/pistons with them still in the car that would help me decide if I should replace the rings, particularly the oil ring?
 
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Dieselmonkey02

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If you have it apart might as well just put the new rings in imho. Make sure all the ring gaps and clearances are good. There's probably a spec on ring tension if you want to get anal or real precise, new rings would probably require a light hone to break in right. If there's much of a ridge at the top it should probably be cut down so it doesn't interfere with any new parts if you put any in. You just have to make the judgement calls.
 

rocketscience

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Olympia WA
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96 B4v Passat TDI Wagon
This is a very long overdue followup for this thread but maybe it will help someone. I replaced the head gasket, the head was within tolerance in flatness but I did sand it slightly with sandpaper glued to a section of granite counter top. The head gasket didn't show any obvious signs of leakage. After getting it back together there was no more persistent pressure in the system and I stopped losing coolant.

I ended up finding a pretty badly eroded piston and slight cylinder wall scoring in one cylinder. My guess was that it was from excessive EGT's on mountain passes from the larger nozzles the PO installed. In vagcom the nozzles showed very similar fuel usage across the four, so I don't think one was leaking. I ended up getting two new (used) pistons from Frank who also balanced the set and gave me a ton of advice (thanks Frank!). I honed the walls thoroughly until my fingernail didn't catch the scratches. They all measured well within spec with a micrometer. I put in new rings, bearings and replaced pretty much all of the engine seals, vacuum pump seals etc.

In the several thousand miles that I drove after this, oil consumption was a little less but still close to where it was before. I know my repair could have been more thorough but also suspect that the car needed a turbo, that the seals were leaking. I also installed an EGT gauge and could definitely see where I was probably pushing the limits before.

Anyway, I hope this helps someone. I sold my TDI a while ago and have not been on the forum in ages but am really grateful to everyone here for all of the knowledge shared, it helped me out big time.

Cheers!
 
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