Glow Plug change and compression results
 

Changed the glow plugs today. Removing the injector lines is pretty much an absolute. How easy is it to strip the threads on the injector? :o

Compression test results were:

No1 320
No2 280-290
No3 315
No4 360
No5 315


I measured through the glow plug hole. I cranked until the needle wouldn't go any higher, probably 10-12 cranks. Maybe I didn't do something right cause No4 couldn't be that high, right?
Is No2 cylinder possibly a problem? Maybe a leak down test is in order.
Also, there was some whitish residue on GP #2.

Appreciate the help.

Did you perform a very careful valve adjustment before performing the compression test? There is more variance than I would expect.

Luke, its been a few thousand since I did a valve adjustment. Not beyond the recommended interval though. I forgot to mention this engine has 300,000 miles on it. I've been noticing some lack of smoothness in the idle at times (after hard runs), also more smokiness out the tailpipe (not white).

That is within manual specifications
 

The max that the Mercedes manual says you can have on a piston is 420psi.

Well, the 617 manual isn't that forgiving.
The normal range is:
22-24 kilopascals or 320-350 psi

minimum is 15 kpascals or 220psi

Permissible variance between any two cylinders is 3 kpascals or roughly 45psi.

I've got a maximum deviation of about 70psi with a deviation of 30psi or so between the other cylinders and the low one.

Oh and now I find the torque spec for the injector lines is 25Nm. I hope I didn't overtighten them. One of the throttle linkage mounts in the valve cover stripped out. :(

I herd that on junk Jaguars you can:
 

Pour either ATF or a little oil and it would help give them better compression and make them run again. This was on the cars with Nickasil. I do not know if it would help or not. I probably would not try it but just thought I would mention it.

I thought you squirted some motor oil in the cylinders and recheck compression. If it goes up, you have bad rings. If it remains unchanged, either the head gasket or valves.

I have heard for compression test too.
 

I have also heard that it is supposeto raise compression too for a little while in its running. Only about 20,000 miles from what I heard.

Squirting oil into the cylinder would help compression if you have worn rings. The oil will help seal around the rings. This would have no influence on leaking valves. This was a common way to help diagnose worn rings on a gasoline engine. I would not recommend this for a diesel engine for a couple of reasons. First of all, oil is combustable and your engine is designed to burn oil. You run the risk of having the oil ignite during the compression test. This is dangerous. Your compression guage can probably handle 500 psi but not if that cylinder ignites. The second reason I wouldn't do this is the amount of clearance you have between the piston and the head at TDC is very small. If you squirt too small amount of oil into the piston, it will just sit on top of the piston and not get to the rings. If you squirt in too much you could run the risk of hydraulicly locking your motor or bending a rod. The third reason is the benefits are short term. As soon as your cylinder starts to fire, the oil will burn off. As soon as the plume of smoke behind the car disappears, so is the oil you squirted in the cylinder.

If you are squirting oil into the cylinder to help free sticky rings, then that's a different story. I have heard of folks using everything from Marvels Mystery Oil (MMO), ATF and WD-40 squirted into the cylinders with some success. In this case it's important to crank over the engine several times with the glow plugs or injectors removed so excess oil can escape without locking the engine.

TimK