10 replies to this topic

[Danmini]

Hi, my apologies for being very stupid.

I have read the Haynes manual re: compression testing, but I just don't understand the 'have somebody hold the throttle open while you turn the engine over on the starter motor' bit?

Can anyone please right a quick 1-10 for dummies on carrying out a compression test?

Also if anyone has any thoughts on the following: I have recently replaced the primary gear oil seal, found oil in the flywheel housing, but I suspect it's leaking again, hence the compression test? Can anyone offer any advice?

Thanks for suffering a fool.

[starletman]

Only ever done two or three,but have always removed one plug at a time screw in compresion tester and get some one to start the car or just wind it over while you check meter reading,you only need to run the car for a few seconds to get a reading then move on to the next plug.

[stevede]

Hi, my apologies for being very stupid.

I have read the Haynes manual re: compression testing, but I just don't understand the 'have somebody hold the throttle open while you turn the engine over on the starter motor' bit?

Can anyone please right a quick 1-10 for dummies on carrying out a compression test?

Also if anyone has any thoughts on the following: I have recently replaced the primary gear oil seal, found oil in the flywheel housing, but I suspect it's leaking again, hence the compression test? Can anyone offer any advice?

Thanks for suffering a fool.

A compression test is to check for bore / piston ring wear.

A leaking primary oil seal will not be connected in any way.

Is this the only reason you want to do the test?

Regards

Steve

[Danmini]

Cheers guys.

Steve couldn't one of the cylinders be split and pressurise the sump? Causing more pressure on the seal? Or maybe the breathers/hosing could be blocked causing the same problem?

It's not runnin great anyway, so think the test might help to diagnose any issues?

[mars red mike]

Cheers guys.

Steve couldn't one of the cylinders be split and pressurise the sump? Causing more pressure on the seal? Or maybe the breathers/hosing could be blocked causing the same problem?

It's not runnin great anyway, so think the test might help to diagnose any issues?

When my clutch wore out very early on due to a leaking oil seal, I took the breather canister of the flywheel housing to find that it was choked solid with crud. It was so bad that I filled one end of the breather with thinners and over an hour later still nothing had appeared at the other end. I have never seen one blocked up so bad before. I ended up poking all the wire wool out with a screwdriver and replacing it with new stuff. Since then all the other little oil drips have stopped as well.

[johnnyspencer]

to do a comprssion test your engine must be up to running temp and all plugs removed, put your foot flat down an the accelerator peddle and turn the engine for about 3 seconds, repeat on all cylinders.

[Danmini]

Thanks mars red mike.

Checked compression today and all cylinders around 165-170psi. Phew.

I bought a 'new' Clutch housing breather (seems to be a recon'd one) from minispares, as have been told as you say mike that the breather could be blocked. Tried to fit it today but with the engine steady repair kit i have it won't go back on... Frustrating to say the least. Having to find a fix for this!?

How easy is it to fill the breather back up with gauze? Because I cld just do this with my original one and get the £28 back from minispares?

[bmcecosse]

The advice to run the engine is very bad indeed. Leaking seal is indeed VERY likely to be caused by pressure in the crankcase - so indeed clean all breathers and make sure one of them is connected directly to the carb to suck away any fumes........ DO NOT use the daft 'breather filters' that some sell. As a quick check - hot engine idling - remove the oil filler cap and rev up - is there a pluime of fume/smoke ??

Edited by bmcecosse, 29 December 2010 - 05:42 PM.

[cooperrodeo]

Are you sure the oil seal is OK? You have to be careful when pushing the clutch housing on. You often need to help the seal expand on to the primary gear as the seal can be pushed inside out and the spring in the seal can come adrift.

Edited by cooperrodeo, 29 December 2010 - 06:16 PM.

[icklemini]

seal could have been split when fitting (as above), could also be wear in the primary gear bush.

yes excessive crank case pressure could cause it to blow, but to be honest a compression test wont really find that - a leakdown test would be better to assertain the leakage of the cylinders and where its leaking off to.

[Danmini]

Thanks for the advice. Have run compression test and as stated seems fine.

Today I replaced the Flywheel housing breather and cleaned all pipes. I'm concerned about the timing cover breather though when engine is idling it doesn't seem to have any air pumping through it at all, compared to the flywheel housing one which has a flow constantly? Is this correct?

I tried to clean the timing cover breather but it wasn't easy. I really don't want to be replacing the timing cover if I don't have to seems like a big job! But need to reduce the pressure in the sump!