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Odd leakdown test, good compression, advice needed

Hello, Helped some relatives find an inexpensive and good car, exhaust leak sound near the manifold or downpipe. Needed a timing belt. it smoked like the dickens off idle, and had a nasty clatter near #3. I figured it needed valve stem seals, maybe lifters, if it needed guides throw on a $150 used head worse case scenario. It ran like a top though, so I knew the problems weren't terminal.

It was one owner and spotless otherwise so I recommended they purchase based on fixing it. I was expecting good compression & good leakdown, so figured we would do valve guide seals & a head gasket when we did the timing belt and give the head a general look-see, if it looked OK proceed to a guide wobble test, and some minor valve lapping & checking the seal with prussian blue. Check for warpage on the lathe ways, and have an automotive machine shop deck .010 if that was the only issue. Since I could do this in less than a weekend, and they were family, I wanted to be nice and help as I am the family "car expert".

If it helps it is a 2000 VW 2.0 AEG motor, as in NB, GTI, Golf and Jetta.

So, they buy it and I run a compression test, 225 PSI on 1,2,and 4 #3 is 226 for some reason.

Then, the leakdown test. Cyl's 1,2, and 4 are 95% cyl 3 is 70-75%

15-20% deviation is too much. The hissing is from the valve cover, and loud.

Genrally from the valve cover means rings, but the valvetrain clatter being at #3 is too much of a coincidence. as is the smoking only off idle, rings would be smoking all the time. The compression on that slug was higher as well???

My favorite theory is that the head gasked has failed between the cylinder and an oil drain galley. When the engine was idling there is/was not enough vacuum to suck the oil into the piston, but hit the gas, let the throttle snap shut and sluurp, sucks a big bunch of it in there. When you are running down the road the oil is being flung everywhere or perhaps little bits at a time get sucked in as no puddle can form. Since I couldn't find the source of the exhaust leak, 20% of combutsion on #3 going into a valve cover unmuffled would perhaps make the same sound. Since this cylinder gets a bit of oil all the time that might explain the 1 pt higher compression? The plugs looked OK, but I figure that most of what is happening is exhaust going through the hole into the valve cover, not the other way around.

One other other theory is that there was a timing belt incident, a valve was bent, and has subsequently destroyed a single guide. the valve is not closing completely. This doesn't explain the hiss in the valve cover though, nor would a sticky valve due to carbon, making this theory second. However, there were a few oil spots on the inside of the overflow tank making this idea more viable. No oil in the coolant or coolant in the oil right now, but If they continue driving it who knows. If the belt break caused a crack in the head, that could explain the symptoms as well.

I told them not to drive it and I explained that if the gasket fails, the piston could hydrolock and bend/break rods/crank, if a lifter jams, the valve could break the piston, or if the valve fails, same thing.

Against my advice they are driving it daily, and have insisted the leakdown is immaterial, and they don't want a headgasket. They are putting their time into washing and waxing it instead. They want me to do just the timing belt, but I will not without taking the head off too.I don't want to touch a hot potato.

What do you all think about my diagnosis, the condition of the car, my dire warnings etc? I am curious if any other experienced mechanics would say to drive it in this condition and what they might think is the issue. Would you do just the timing belt?

thanks,

devnull

Reply to
devnull
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Devnull,

They need a rebuilt head on that thing, the valves are worn in the guides, seals are shot, etc. If a snapped belt bent a valve then the belt on there would be new, right? It's probably just all carboned up in there due to excessive oil leak past the valve seals.

But, you got a bigger issue than that.

Simply put, you told them not to drive this and they are ignoring your advice. Even if you are wrong and the car is OK to drive, the fact is they are using/abusing you for car repair assistance and your telling them to do something and they aren't doing it. Your word should be law to them on this. If not, you need to tell them "sorry, I told you not to drive it until I got it fixed, your ignoring my directive, your on your own with the timing belt and whatever else" and just turn and walk away from it.

When they are ready to do as you tell them to do, then be happy to help them out. But it may take a few blown up engines for that and a few times of biting your tongue instead of saying I told you so.

This is a professionalism thing. If they aren't doing as you tell them they then have no respect for your abilities and if you touch their car and -anything- goes wrong with it, even if it's at the other end of the car and has nothing to do with what you touched, they are never going to believe that it wasn't you that caused it, even if the Pope himself tells them.

If they paid $100's of bucks to a mechanic would they ignore that person's directives? Of course not. The fact they aren't paying you labor should not make a difference. Obviouosly it does or they would be doing what you told them, so you need to just let them alone right now.

Ted

Reply to
Ted Mittelstaedt

Thanks Ted,

I did basically tell them I would not help until the car passed leakdown, or we were doing the head & TB at once. I even gave them a second chance saying that I would do it all this weekend if they would like, not only did they refuse, they decided to have another relative that has never touched a VW do the timing belt.

I figured my best bet was to make sure everyone else in the family knew I receommended the car only with the repairs I specified, and they are now doing something I did not recommend, in the strongest terms I could muster. I don't want to be blamed for picking a "lemon" as it wouldn't be a lemon if they would let me fix it. They have agreed to this over and over again, saying it will be fine and they will just put a gasket on when it gives out (famous last words, heh.) they will have a hard time pinning the eventual meltdown on me.

Older VW's are easy to work on, newer VW's are easy to work on if you know them, and a nightmare if you don't. The other relative has a 50/50 shot at getting it right. The timing belt runs the water pump, so since they are doing it half-assed they probably won't replace it, leading to another TB change when it leaks all over the place in a few months. They claim they are doing all of this to save the $350 in parts I specified. They paid $2-3,000 under retail due to my help and advice, and they can't spend this much on it? They will probably skip the tensioner or use the chinese one from autozone. I only use dealer parts in critical areas such as this.

I warned our other VW savvy relative that they may get a call if the VW Buying relatives mess up the TB or if they explode the motor. I warned him as you warned me that no matter how good a job he did, he would get blamed if it blew up. As you say, a good mechanic would never knowingly leave a ticking time bomb. He, as I, is very helpful by nature and may have agreed to help without thinking about what a mess it could be. I respect him and don't want him to get taken advantage of as I was.

I agree, it is completely disrespectful to take up 5 or 6 of my evenings, two weekends, and then tell me I don't know what I'm talkng about. They are pulling defeat from the jaws of victory with this one. I am unlikely to bail them out if the engine is destroyed, they need to pay full freight for this repair to learn how valulable certain kinds of help is and that they shouldn't tick off the free mechanic. Plus, an engine swap is 10x more work than a head gasket, and I have better things to do than reward their hubris.

Funniest part, they took a trip right after they bought the car and while on the (likely expensive) vacation they bought a $300+ digital camera that they "needed."

take care,

devnull

Reply to
devnull

with good wanna help intentions - you might be being a little hyper in you fix-it upper program.

I'd think about bringing the scheduled maintenance items up to date (*fully), and change the timing belt only if it was evident there was a need, or mileage dictated such.

Then, if it blows - exchange it, no big deal.

*there is a raft of these, address each one.

mho vfe

Reply to
fiveiron

On a mk4 2.0 VW you have to change the timing belt unless you know it has been done right, as if they fail since it is an interference engine it will be an expensive repair if it does. Mileage dictates that it is neccecary and the seller had no idea if it had been done.

Most of my "fix it upper program" is to repair things that are obviously broken. Some of the items I described would only be neccecary if problems were found, or would take little to no extra time with the head off.

In essence, there is a headgasket leak, bad valve & guide, or crack in the head and exessive lifter noise. When you run a bad component to failure, the results are unpredictable. The timing is unpredictable as well, it will go when you are farthest from home or when it is the most inconvenient.

My "hyperactive" program was essentially 1) take off head 2) make sure its good 3) put back on and use new timing belt. I feel this is the best plan as a used engine is $1500-$2500 + labor* and a headgasket is $100. Any machine work dictated by head condition is still cheaper than the engine.

thanks,

devnull

  • My time has value to me, so 4 hours of head work vs 12+ hours of engine swapping work matters to me.
Reply to
devnull

I'd be thinking head gasket, and bad valve[s] at the #3 cylinder, possible bad rings on #3 also. The symptoms you describe lead to it. You could suggest they try some of the chemical fixes on the market, such as poru-in leak sealers, decarbonizers, valve quieters, but I'm sure you know they at best are only fast fixes for a problem requiring repair.

Reply to
Knifeblade_03

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