Engine is a d16y8 out of a 97 ex. with 330,000 mi. I need to do a rear main and front crank seal replacement as well as a timing belt, water pump, tensioner etc etc. Was wondering if I should do new piston heads, rings, main and rod bearings, etc etc while the engine is apart. Here are my compression results today.
cyl
#1 - 180psi
#2 - 150
#3 - 165
#4 - 170

thinking that #2 being lower is due to maybe a valve not sealing?

should i rebuild? if i dont need to rebuild....i won't have to pull the engine. i will do a gasket and seal kit regardless. any input is appreciated.

 

Put a cap full of oil into the cylinder and redo the compression test in the lower cylinders, see if it changes.

also do a leak down test as that can help diagnose what is causing a loss of compression in the cylinder.

 

I second the cap full of oil. If the cylinder walls are dry the ring seal isn't as great. 150 isn't really that low I'd be more worried about the inconsistency between cylinders.
leak down test isn't a bad idea.

 

Also, was the compression test done with the engine at operating temp or cold?

 

Will do. Thanks.

Ok I will redo today.

 

Ahh..didnt even think about it.....so it was cold.

 

Those are pretty decent numbers for cold dry test.

Also when you did the test did you do a specific amount of cranks each cylinder or cranked until compression didn't go any higher?

 

thanks for your help. I cranked it until the needle stopped going up.

 

Okay, that's more of a max pressure sort of test and not a solid indication of engine health.

The typical method is on a warm engine (15 minutes off after running at full temp) you crank each cylinder a set amount of times. Typically it's 4 or 5 cranks (You have to decide if you are doing 4, or 5. Just be consistent with which ever number you choose. Do all 4 or do all 5, don't mix and match.). Record the numbers. Then do the same for the wet test, dribble a little oil in then do the same 4 or 5 cranks. Record all the numbers.

Doing it this way will really give you a good idea of the engine health.

The reason the max pressure isn't very informative is even weak rings will eventually build up decent pressure if given enough time cranking. That's also why a leak down test was suggested, it is quite informative.

 

ok, so what if my battery starts to get weak? Wont that have an effect on compression readings if I limit the number of cranks? Because my battery sounded a bit weaker after the first cylinder. Thanks again.

 

If your battery weakens from a single short burst of cranking, then you have other issues you should also be concerned about.

You can always use a jump box or battery charger with a jump start setting to supplement a weak battery.