QuestionQUESTION: I just completed compression and leakdown testing on my 1800. The results were compelling:
1: 125 psi, 1% leakage
2: 110 psi, 30%
3: 0 psi (not a typo), 95%
4: 65 psi, 95%
Where do I go from here? Anything else to check out before I pull off the head? What will be the procedure for checking the valves, rings, bearings, etc?
Thanks!
ANSWER: Hi Billy,
There are some other tests you can run to have a clear picture of what you need to do.
First check valve clearance to be sure there are no tight valves.
Pull all the plugs and spin I engine for a minute or two and note the oil pressure. You should see 35 PSI. this is a rough check of bearing clearance. Run the compression test with 4 or 5 squirts of engine oil in the plug hole. This (Wet) test will check rings and should not be any more than 10 to 15% higher than the first (Dry) test.
Then get one of those fittings that adapt your air hose to the spark plug hole. (most tool trucks carry them)
Put the piston on TDC of the cylinder to test. Hand brake on hard and gear lever in 4th gear. Apply air (125 to 150 PSI) to the cylinder, then listen at the carb for a hissing sound. (no sound should be heard)then listen at the tail pipe (same)
Even though you can hear hissing in the crankcase with the oil filler cap off from ring leakage but unless you have listened to a known good engine it is difficult to distinguish the difference.
Another test you can do on each cylinder while you have pressure on it is to open the radiator cap and watch the coolant level. It should not raise when pressure is applied. I found this test to be so good that it can pick up a minor leak that didn't even cause any overheating.
I found that this air pressure test was a 100% effective test for valve tests and for head gasket tests.
Let me know how you do.
Howard
---------- FOLLOW-UP ----------
QUESTION: Thanks! Adjusting the valve clearance certainly changed the picture, raising compression on 2 and 4 to 125, and on 3 to 50 psi. The wet test didn't seem to show much difference, good news. The pressure/leak test indicated exhaust 3 and intakes 2 and 4 were bad. Pulling off the head and putting kerosene in the valves confirmed this.
So the good news is, the engine appears salvageable. The head's at the shop now getting estimated.
However, I forgot to run the oil pressure with the plugs out. I did test the oil pressure with the engine running, and got 25-50 psi at idle, 50-70 at speed. The lower numbers were when the engine was cold. Does this tell us anything?
Thanks for all your help!
AnswerThe lower pressure readings cold are normal as the oil pressure can't seem to get through that little metal pipe to the gauge and I found that cold thick oil seemed to open the pressure regulator valve easier thus lowering the pressure a little.
Sounds like you have your stuff together on the engine tests. Good luck.
Howard
