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