Engine Compression help needed

[Lucas]

I just did a compression check on a 1994 3.9L Disco. Test was done dry, engine hot ( went for a drive before testing) The readings are:
Left side front to back
148
146
148
145

Right side front to back
149
145
144
144

Seems low? I thought I had a head gasket problem. Exhaust smelled like antifreeze or so I thought. Engine does not burn oil. All plugs look the same. Are these reading normal?

Oh yeah, 126,000 miles

 

[scottjal]

I don't think you have a head gasket problem with them all within 5psi of each other.

From RAVE:
Expected readings, throttle fully open, battery
fully charged:
8.31:1 = 10.2-10.9 bar, 150-160lbf/in 2
9.35:1 = 11.5-12.2 bar, 170-180lbf/in 2

I would guess that you are fine with an engine of that mileage? Anyone know what the compression on that engine is? Suposedly stamped in the head above the serial number.

 

[Chris-St Louis]

Its a 9.35 on a 94.

Those numbers are low, but consistant with 125k of wear. Your looking for them to be within 10% of the other cylinders, which yours are.

Smell your coolant, does it smell like exhaust?

 

[Lucas]

Its a 9.35 on a 94.

Those numbers are low, but consistant with 125k of wear. Your looking for them to be within 10% of the other cylinders, which yours are.

Smell your coolant, does it smell like exhaust?

No exhaust smell in coolant. Guess this is good news?

 

[Chris-St Louis]

Good news indeed. I would keep a eye on things, but its too soon to do exploratory surgery right now.

 

[Lucas]

Great!

Last year I changed the valley gasket. I saw that the cam was worn and am planning to do a top end rebuild next spring. Would it be fair to say that if I do a valve job with the rebuild that a lower end rebuild could be a long way off? I often hear of these engines having 200,000+ miles without changing anything on the bottom end. The lower compression readings are making me question that now.

 

[Chris-St Louis]

I would, if it were me, do the valve job and worry about the lower end when it fails, if ever.

You could pull a bearing cap off and look...Use that as a gauge.

There is about 50 ways to skin this cat though...No wrong answers.

 

[Lucas]

I would, if it were me, do the valve job and worry about the lower end when it fails, if ever.

You could pull a bearing cap off and look...Use that as a gauge.

There is about 50 ways to skin this cat though...No wrong answers.

Thanks Chris. Sounds like good advice. You made my day.