Old Library

Is it possible to do a leak down test at home on a 98 GTI VR6? I would
assume it can be done with an air compressor and an adaptor for a spark plug
hole, but I am unsure of the pressure, and feasibility of getting an air
line to the plug holes. Any ideas on if I can do it and how? Or should I
just take it to VW? Thanks.

why not do the opposite and simply run a compression test?

Gavin

I've done it to my 16V Jetta before at home, and I don't see why it wouldn't
be feasable on the VR6. I am sure that my uncle has done it before on his
VR6. Should take about an hour if you have all the tools.

You need an air compressor, a spark-plug-pressure-gauge-leakdown-tester
doohickey (I think that is the technical name), a jack, jack stands,
flashlight, and some welding rod or other long thin object to determine TDC.

Basic process:
1. Find TDC on cylinter one using tranny marks
2. Test that cylinder 
3. rotate enginer to TDC on next cylinder 1-5-3-6-2-4 see
http://www.houseofthud.com/firing.gif
4. repeat steps 2 and 3 for all 6 cylinders.

As to why do a leakdown test, that can often tell more data than a
compression test because you can find out what part of your engine isn't
holding up. If you hear hissing in the intake, it's your intake valves not
seating. If you listen to the exhaust pipe and hear hissing it's your
exhause valves. If you can't hear either it's your rings. If you hear air
coming out of the side of the motor you have a serious problem. :)

Peter J.
Club H2O Atlanta/GA Rep
http://www.clubh2o.com
&#112;eter.jolles&#64;ps.ge<img src=/i/dc.gif border=0 width=35 height=15>

Any of you guys ever did a compression test on your VR and what are the
results. A friend of mine did it and got 180 is that ok?

I did one recently on my 1995 with 120K on it.  The highest was in the mid 170s and the lowest in the very high 150s, within 10% of the high.  This was well within the tolerances in the Bentley manual.
Cary

Yeah, but the tolerances of the Bentley manual are
pretty wide.  If my motor was on the lower end of the
Bentley tolerances I'd be pretty worried.

-josh

Roger,
It isn't necessarily the number that is important.  The number should be
within an acceptable range (Bentley) but, what is more important is the
variance between cylinders.  If all cylinders measured about 180, I would
speculate that your motor is in good shape.

Gavin

Guys,

Is a compression test something that a Do-It-Yourselfer can do?

-Costas

If you can put in a sparkplug, you can do a compression test. A cheap tester
is only $30 or $40. Of course putting a sparkplug in a VR6 is no simple
feat. Especially without the right tools.

it is a one friend and a 2 beer kind of job.  all you do is, remove the
spark plug & wire, then screw the tester guage into the spark plug hole.
crank the engine and read the guage.  replace spark plug & wire then repeat
for all cylinders.  I am not sure if you need to disconnect anything else
so that you don't get a fault code.  I have never done it on a computer
controlled car. Refer to the Bentley Bible for more details.

Gavin

New here, Hi everybody! The way I have always been
told and always done my car is, have the car up to
operating temp, pull the fuelpump fuse, start the car
to drain all the fuel from the line/injectors, remove
all sparkplugs, hold throttle wide open while cranking
the engine when testing each cylinder. Crank the
engine over 4-5 compression strokes per cylinder. Its
always given me accurate readings.

Sean