[Vwdiesel] 1.6L Diesel Compression

[James Hansen]

Bentley isn't so much a step by step how to manual as a factory service 
manual that assumes you have the basic resources of a journeyman or 
apprentice.... meaning the only thing they will identify is volks 
specific or specific procedure related things.  It is accepted practice 
to squirt oil into a hot gas motor to check if the low pressure is rings 
or valves on a compression check.  It's not a good thing on a diesel, 
specially if you are doing it hot or very warm, which is the standard 
testing mode for a compression test.  Loren was lucky.  Local dude blew 
the gauge across the shop, and ate some glass.

A leakdown test is by far better, but a tremendous PITA to accomplish 
compared to a compression test. I hate doing leakdown tests, but you can 
do them anytime on a cold motor.  Trick is to keep the motor from 
turning.  It's easy to do on an airplane, pretty sucky on an auto engine.
-james

Doyt W. Echelberger wrote:
> I re-read my Bentley on how to do a compression check on a VW diesel, to 
> see if there was any mention about doing the check on a hot engine.
> 
> Bentley doesn't actually say what the temp should be, but it describes 
> preliminary work that would take_ me _enough time for the engine to cool 
> off considerably, if it had been warmed up: Bentley describes disconnecting 
> the electrical wire from the stop control, removing the injector pipes and 
> the injectors, and then putting the compression checker in place and 
> testing each cylinder. And those checks are done without squirting in any oil.
> 
> The suggestion to squirt in some SAE 40 into the cylinder is for 
> determining what is causing a low reading if you get one....so that would 
> happen only after testing all the cylinders and comparing the readings 
> .....which would allow a hot engine even more time to cool down.
> 
> The one time I checked compression (about 7 years ago) was on a cold n.a. 
> VW diesel that had stopped running for unknown reasons. So, there wasn't 
> any question of working on a hot engine.
> 
> Doyt
>  >>>>>>>>>>>>>>>>>>>>>>>>>>
> At 08:18 PM 11/24/2007, you wrote:
>>   Problem is you're supposed to check compression on a hot
>> engine.  Add oil, plug the one hole with a compression gauge
>> and viola!  You get compression ignition using the oil as fuel!
>>   Not likely to happen you say?  I had it happen on a Stock,
>> Ford 302.  Pegged the gauge and it stuck there.  Trust me,
>> I'll not ever try it on a diesel (so long as I'm actually thinking
>> about what I'm doing!)
>>      Loren
> 
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