• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

Compression test on dry engine

tomasss

tomasss

former PRVert
Joined
Oct 13, 2008
Location
Sydney, Australia
Ok, so I have engine out of the car.
The engine had an excessive crankcase pressure, PO stated it is most likely because of the blocked PCV. Anyways I wanted to take it out to replace the transmission and do some other mods, so not a big deal.
After draining all the fluids and finishing some other tasks, I came back to the PCV...but found out there is no blockage whatsoever and all hoses are ok.
So now the question is...can I do the compression test without damaging things on the dry engine? I need like 5 revolutions per every cylinder...
Cooling is not a problem but the lubrication...?
 
Cranking speeds will not cause an issue. Assuming it had oil in it within the last 6 months or so? Over *very* long periods of time, all the residual oil can slowly leave the bearings.

on a broken in engine, the oil is almost more for cooling that lubrication. And no cooling needed at cranking speeds.
 
You could always just take the timing belt off and prime the oil pump by spinning the aux shaft with a power tool.
 
^^^ you can also do it by hand with a socket wrench and 6" extension if you have good stamina. Peek in through the oil cap and keep cranking until you see the valve buckets fill up with oil.

For OP, often you'll do a compression test first with the cylinders as-is. If the readings are low, you then squirt a little oil into the cylinders and do the compression test again. The extra oil will cause the rings to seal better and can help diagnose low compression due to ring leakage versus valve/gasket leakage.
 
There is a tool for old GM engines where you remove the distributor and install the priming tool to the oil pump driveshaft, attach a drill, and prime.

On old Volvo, especially on a costly rebuild, I would probably enjoy priming the engine for a peace of mind. Pull the oil filler cap and prime at least until clean oil is seen coming from the cam bearings.

Glad to hear the suggestion was appreciated. I'm still learning many new tricks an methods from the old timers at the shop.
 
ZVOLV said:
You could always just take the timing belt off and prime the oil pump by spinning the aux shaft with a power tool.
Click to expand...

Bullu.jpg
 
You must log in or register to reply here.
Back
Top