Help please

G

glanza97

UNTRUSTED SELLER
Hey guys, my mate cooked his car, not sure how or why? Anyway, headgasket went... had his head skimmed, new headgasket... just put it all back together.... not started it up yet because he has no oil.... but done a compression test....

1 reading around 150.... number 2,3,4 all reading v low... around 50's etc i think he said....

just wondering what may be the problem, i thought of the timiing but if it was the timing I thought they'd all be out...?

Maybe rings?

any input guys...? cheers
 
GTWorld

GTWorld

Member +
mmmmm Thats a werid one i would have thought piston rings going would cause the compression to drop that much?
 
G

glanza97

UNTRUSTED SELLER
i was thinking maybe the rings too... what I dont get is why he didnt just pop them out when he took his head off :S guna b a long night i think :(
 
Texx

Texx

Super Moderator
glanza97 said:
not started it up yet because he has no oil.... but done a compression test....
Click to expand...


So theres no oil in the engine?

If no, I'd get some oil in there, run the engine to operating temperature and carry out a compression test again.
 
GTWorld

GTWorld

Member +
glanza97 said:
ooo right, im not sure mate, hence why im here.. :)
Click to expand...

But like everyone has said oil in first mate!

As a rule, most engines should have 140 to 160 lbs. of cranking compression with no more than 10% difference between any of the cylinders.

Low compression in one cylinder usually indicates a bad exhaust valve. Low compression in two adjacent cylinders typically means you have a bad head gasket. Low compression in all cylinders would tell you the rings and cylinders are worn and the engine needs to be overhauled
 
GTWorld

GTWorld

Member +
glanza97 said:
so what about low compression in 3 cylinders? does that mean no oil :p
Click to expand...

Lol,

If compression is low in one or more cylinders, you can isolate the problem to the valves or rings by squirting a little 30 weight motor oil into the cylinder through the spark plug hole and repeating the compression test. The oil temporarily seals the rings. If the readings are higher the second time around, it means the rings and/or cylinder is worn. No change in the compression readings tells you the cylinder has a bad valve.

Hope all this helps
 
G

glanza97

UNTRUSTED SELLER
GTWorld said:
Lol,

If compression is low in one or more cylinders, you can isolate the problem to the valves or rings by squirting a little 30 weight motor oil into the cylinder through the spark plug hole and repeating the compression test. The oil temporarily seals the rings. If the readings are higher the second time around, it means the rings and/or cylinder is worn. No change in the compression readings tells you the cylinder has a bad valve.

Hope all this helps
Click to expand...

cheers batman, will see what i can do :)
 
MeisterR

MeisterR

Lifer
Had a similar issue when my engine was being rebuild, number 1 was down a bit.

So we decide to map the car and see if things get worst as I would need a new block (already overbored) rather the engine surrive or not.

Once we got it running for a while and hot on the dyno, we did another compression test and the level have even up again.
You just might have "sticky" ring and need some pressure to pop it back out.
 
HYBRID

HYBRID

Super Moderator <a href="http://www.toyotagtturbo.
Sheldon said:
why did he crank it without oil??
Click to expand...

thats what im trying to figure out.. he could have easily damaged the engine bearings/oil pump by just trying to crank it with no oil.. thats some crazy shit trying to do a comp test with no oil..

also how do u expect to run a comp test & get good results when u have no oil? oil flow/pressure plays a very important part in sealing the engine.. dont expect any accurate results without oil!!

kon
 
MeisterR

MeisterR

Lifer
Oh, I miss that bit... I was under the assumption that there was oil in the sump as I didn't think anyone would ever crank a engine without oil.

In which case... yea... there is no way you would get an accurate result, and just hope it didn't do any damage.
 
You must log in or register to reply here.
Top