Thread: 300TDI very very high compression!!!

first up remove the injectors, pull the solenoid wire and crank the engine over to clear the pots.

then do your compression test.

if its spitting out liquid and wont stop, theres your answer.

Thank''s for you answer Dave,

What would it mean if liquid is coming out, and from where?
And do I put the injector back when I do the compression test ?
And what would be the liquid ?
And I have a weird thing going on, when I try to do the compression test, the little valve in the tester just keep breaking. I change the vale and it do the same thing again and again.

Thank's again,

Matthieu

which compression tester are you using?

you need to work out what the liquid is, it will be either oil or coolant.

I am using a ultrapro diesel compression tester.

Can you explain me from where the liquid would spill out and what it could meen ? And the liquid would come out when I do the compression test ? I put back the injector in ?
And some people have told me that the head that have been skim twice is good for garbage and that this is why the compression is so high.

what do you think ?

Hi Matthieu.
Ok, when an engine is healthy, and a compression test is undertaken, each time the piston comes up and a reading is taken, there is a certain amount of 'blow by'... This means that some of the compressed air is escaping down the side of the piston... Giving you your lower/normal reading. If however you have an internal engine issue (which it sounds like you have) and there is oil or water getting into the cylinder, this 'liquid' helps form a seal between the piston and cylinder bore, and in turn causes a higher compression test reading......

Now, we are assuming you are doing a compression test using the starter, and not allowing the engine to run.... Secondly, if you are getting those high readings, how is it starting...? Thirdly.. You talk of liquid... If there's liquid, then there's smoke.. (You imply there is no smoke).. There also has to be fluid level loss in the sump or radiator... As you've decided to investigate by doing a compression test, and you say there is coolant coming from the head, we can reasonably safely assume that the head gasket has failed, or the head is cracked... Are there any low compression readings within the 4 tests? Has the engine ever been boiled or got hot?

My advice would be to take a step back, look closer at the symptoms, what's happening, oil colour, coolant use, coolant colour and activity (start engine from cold with radiator cap removed and watch for rapid coolant departure from header tank..), any water from the exhaust, any steam from the exhaust, any misfire, etc etc. Time spent now with a decent diagnosis will help you in the long run. Good luck, and let us know what you find. Pics and videos are good as they tell a 1000 words! Cheers. Simon.

Originally Posted by Matthieu

I am using a ultrapro diesel compression tester.

Can you explain me from where the liquid would spill out and what it could meen ? And the liquid would come out when I do the compression test ? I put back the injector in ?
And some people have told me that the head that have been skim twice is good for garbage and that this is why the compression is so high.

what do you think ?

depending on the depth of the skim you can get away with a couple of shots at it BUT it wont last long if the material at the surface isnt at a certain hardness.

skimming the head does raise compression but not as much as you're experiencing.

IF you havent disabled the fuel injection when you crank the engine over you're going to be reading combustion pressure not compression. If your reading combustion pressure your going to want a gauge that can handle upwards of 2000psi. (and truth be told Id be wanting a guage that could do minimum of 5000psi)

Oh my god,
I have been doing the compression test into the heater plug!!
OK, I feel stupid now. After reading all your post I realize I was doing something wrong, I checked into the manuel and saw it!
I will do it right tomorrow and let you know.
Hopefully, everything will be better.

Thank's a lot guy,

Originally Posted by Matthieu

Oh my god,
I have been doing the compression test into the heater plug!!
OK, I feel stupid now. After reading all your post I realize I was doing something wrong, I checked into the manuel and saw it!
I will do it right tomorrow and let you know.
Hopefully, everything will be better.

Thank's a lot guy,

Why would doing a compression test using the hole which the glow plug be an issue????, Even if the head had a pre-combustion chamber the compression it should not be an issue.
My diesel compression tester is designed to screw into the glow plug hole.
As previous replies advised....I would start the motor and diagnose symptoms, a white sweet smelling exhaust is coolant leaking into the combustion chamber.
Are you actually loosing coolant over time? Overheating issues?