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Model Specific Questions and Info => MK2 Golf/Jetta and Audi 5k => Topic started by: thomas m on July 23, 2017, 04:58:46 pm
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Bentley say "normal operation temperature". About 180F for my cylinder head.
Is it a good idea to first remove the injectors with the engine cold and clean the threads and apply some anti-seize?? Then warm it up.
I'm a little concerned about taking the injectors out of a hot aluminum head. I was taught no to do that on my old Beetle plugs.
PS: should all of the injectors be taken out for the test or should it be one at a time???? Would the cold air matter??
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Removing the injectors, yes all four when the engine is cold is a good idea. It is less work on the starter to spin it over that way. I like to work on a less than hot engine most of the time. And I would apply anti-seize to the injectors when I put them back in. But I would do something in between taking them out and putting them back.
I would do a compression test on all the cylinders when the engine is cold. Write down the PSI per cylinder and set it aside.
Now reform the heat shields or replace with new ones, whatever is your preference. Anti seize the threads on the injectors and get the engine warmed up as you say. Take it up to 180 if you wish then you have plenty of heat to burn yourself on getting the injectors out. They should come out without much force now that they have been out just awhile ago. Remember always push the breaker bar or socket wrench towards the head and don't pull away from the head when removing the injectors. A cracked boss is no fun. Well maybe at work once in awhile but not on the engine.
Now do the compression test again. See any difference in the numbers? Rings are seated on the warm engine and should give you higher numbers. Is the desired PSI 480 in the Bentley? And isn't it 10% difference between cylinders another standard you should look at.
Sure the diesel will start on less than the desired PSI but given a very cold morning with a low battery and you will likely be looking for a jumper pack in short order.
Hope this helps. Let us see yer numbers.
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Cold and hot compression test. With all of the injectors out.
Is there any concern about shock cooling the valves??? Or not to worry????
I guess the leak down test could be done at the same time; both cold and hot also.....for the fun of it !!!
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Concern about shock cooling the valves?
You aren't planning to zap your engine with electricity are you?
Pulling air into the engine using the down stroke of the piston is what goes on time after time when the engine is running. I can't foresee it being a problem during a compression test on a hot engine. Worry not!
If you have the equipment to do a leakdown test by all means do it. On the engine cold then hot. What can it hurt? Knowledge is useful and in short supply sometimes.
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Must be the stories my granny told me!!
Thanks for the reassurance.