PDA

View Full Version : Help



flottari
7th September 2010, 08:33 PM
hi all

What is wrong when i get a lot of air coming up the oil filling cap is it the piston with a crack in it or something els

YNOT
7th September 2010, 08:48 PM
What you're describing is excessive blowby. You won't know until you strip down the motor and inspect it exactly what is causing it. What ever it is, it won't be cheap to fix if you have to pay someone to do it.

Tony

ablast
2nd October 2011, 03:28 PM
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.
Checking Compression

Compression can be checked two ways: manually with a compression gauge or electronically with an engine analyzer. The manual gauge method is the only one available to most do-it-yourselfers.

To check compression, all the spark plugs are removed. The ignition coil is then disabled or the high tension lead is grounded. The throttle is also held open. The engine is then cranked for a few seconds using a remote starter switch or a helper while a compression gauge is held in a spark plug hole. The maximum compression reading is noted, then the process is repeated for each of the remaining cylinders. The individual cylinder readings are then compared to see if the results are within specs (always refer to a manual for the exact compression specs for your engine because they do vary from the ballpark figures we quoted earlier).

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.

The same basic rules apply for diesel engines except the compression is higher.

-ET 4wd-
4th October 2011, 12:27 AM
that was super imformative ablast!
Was just about to write it myself!
only thing i would do different is use a bit of trans fluid instead of 30 weight oil, the trans fluid burns off 10 times faster and leaves no residue!!!

Steve.