Jay420

So I finally did a compression test on my XJ. (1992 2wd Sport 4.0 120k miles) Been having some weird problems such as turning the plugs white every couple weeks, losing oil/burning??, possible overheating, and a slight loss of coolant. No temp gauge and my light doesnt turn on, but it definatly seems too hot. Still has loads of power and runs fine otherwise.
Here are my results


Dry Wet
#1 = 110 120
#2 = 120 120
#3 = 120 130
#4 = 110 130
#5 = 122 135
#6 = 125 140

So whats happening? Should I retest? I only removed 1 plug at a time for the test. Would this affect my readings? Did 7 compression strokes, then added a cap of oil and another 7 strokes. Since #2 didnt move is there a bad seal there? I did overheat a few months back and thought I possibly blew the head gasket. But the numbers dont match that diagnosis right???


This is my daily driver so I really need to keep her running. Sorry for the long read but this thing has me confused at hell, and Im not the type of person to guess fixes by throwing new parts at her.

CCKen

Hre's the way you should check compression:

1. Run the engine until hot.

2. Remove all spark plugs.

3. Wire throttle plate wide open.

4. Using the starter (I use a remote starter switch for better control), rotate the engine and see how fast the first pressure appears. Should jump up quickly. Keep rotating until you get three (3) pump-ups. Record the reading after three pump-ups. Try to keep every compression reading technique standard.

Get back with your readings if you can.

Cheers

Jay420

New results are in and arent far off first test. Is this telling me my #2 has valve issues?
Dry Wet
#1 120 125
#2 130 130
#3 130 140
#4 135 145
#5 140 145
#6 130 140

Bbasso

I personally wouldn't worry about that.
Just keep an eye on the fluids and an ear on the sounds.

Jay420

Problem is the fluids are killing my wallet. Quart of oil per day with no visible leaks or crazy oil smell, and full set of plugs every week, sometimes less. Slight knock under acceleration, mostly uphill, but otherwise runs strong. Can lay rubber with the slightest touch of the pedal and ran smoothly 7000kms+ from one side of Canada to the other.

Jay420

Sorry for the double post, but Im thinking . . .maybe I have a messed up cooling system thats killing the plugs, and the oil leak is elsewhere, rear main are does look kinda grimy, and there is oil on bottom of the oil pan, but no drops anywhere on the ground.

Should the top hose to the water pump be too hot to touch??? I only have the idiot light for a gauge so its no help.

Turbo X_J

It's not magic, oil just can't dissappear.

Stand on the gas & look in the rear view mirror, do you see mosquitoes dropping out of the sky?
Park it on a piece of cardboard over night a quart of oil will make a huge mess.

Jay420

Ive tried the cardboard trick and not a drop. I also park in the same spot at work 8 hrs + a day and not a drop. Dont see noticable smoke when laying down the gas. Can smell it a little though so I know she is burning some.

But like you said a quart a day is a lot and should be noticable for a long trail behind me. I drove behind my wife yesterday in a different vehicle and I watched the exhaust. Nothing crazy, no more that other vehicles, and only a small smell when she started from a stop sign.

So where can it be going?

tgordon

White Plug Tips=Lean Burn Condition
Lean Burn Condition=Qverheating
Overheating=Burnt Valves, Blown Head Gasket or Both.
Loosing a quart of oil a day and no visible leak? Possibly get the engine warm then have someone rev it to 1500-2500rpm while you look for where the leak is. Look good at the rear of the valve cover. A lot of oil can get out of there and get sprayed everywhere behind it, concealing the source. You didn't mention any smoke out the tail pipe. No smoke out the tail pipe leads me to think of a rupture somewhere. Carefull visual inspection may locate it.

tgordon

Just curious, what does your air filter and air box look like?

Tobyxj

Are you sure you are checking the oil right ? 1 a day is a lot

Tobyxj

No offence just think its funny checking oil before or after the 420 ?

Bbasso

LOL @ 420

CCKen

Looks like #2 is the only good one of the bunch. If the compression comes up after adding oil it supposed to indicate the rings are bad. The oil seals the rings during the compression check. #1 is a bit low. Normal compression (dry) is 120 to 150 psi. Over all, you ain't too bad; although the rings in #3, #4, and #6 jumped 10 psi with oil added.

CCKen

Concerning having to add oil every day: how many miles do you drive per day?

With the engine at idle remove the oil filler cap and check if there is a blow-by sound coming from the valve train and check to see if smoke/vapor is coming from the valve train. Should be none.