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Need Help with Compression Test Results

So yesterday I went to buy a parts Disco 2 for my 2000 SE7, but when I get there I’m looking at beautiful Adriatic Blue 2004 Disco 2 with a near mint body and interior, seven seats (which I need), and it has the CDL transfer case as well as the proper lever, though I’ll have to source the cable from somehwhere to get CDL functionality. It also has 150000 KMs as opposed to the 300000kms on my current disco.

I paid the man $300 CAD for this beauty (yes, $300 CAD or $5 USD) and towed it home. They reported some constant misfires when running, and ‘a buddy’ came over and cut out the cats, so tow truck it was.

Bottom line is that this Disco is far too nice to use for parts, and I’m going to get it running again and likely end up selling my beloved black 2000 Disco.

There were no engine codes when I hooked up my code reader, no transmission codes, one ABS code, and one SRS code. It was time for a compression test to start figuring out what is wrong with the engine. I removed the wires and all spark plugs (which looked to be original), wedged the throttle body open, and turned up the following results. I ran a dry test first and then a ‘wet’ test.

Dry:
8=180 7=135
6=20(no typo) 5=155
4=80(no typo) 3=155
2=175 1=155

Wet:
8=210. 7=170
6=25(no typo) 5=170
4=100 3=190
2=185 1=180

So at this point I’m looking for some help interpreting the results from those with experience. I could hear a sort of whooshing sound when I ran the test in cylinders 6 and less so in 4. The rest sounded normal. I ordered a leak down tester and was planning on tearing into the intake and harness to free up the valve cover and see if I could find the source of the leak.

I did the headgaskest on my current disco, as well as most of the required servicing and upgrades for those buying a ‘new to you’ Disco 2, so I’m not worried about the outcome, or looking for good news, rather I just want to stay focused on the proper path to fix this baby.

Any and all advice would be greatly appreciated, and if anyone has any idea where I can source a CDL cable that would be great as well.

Thanks so much in advance for all help given!

You may just have a burned valve there. A little more testing is in order.
You can perform a pressure test to pinpoint what's going wrong. You'll obviously need a air to plug hole adapter, sometimes sold to hold the valves closed so you can change valve seals or rockers. You'll need an air compressor, and some hand tools. Sounds like you have most of that plus good skills.

Pull out spark plugs and rotate the engine so that the first cylinder you're testing is at top dead center. Screw your air to spark plug hole adapter in snug enough to seal.
Pressurize the cylinder. 100 psi is plenty.
See if it will maintain that pressure.
Then, open the radiator cap, the oil cap, pull the dipstick, and take off the intake hose. You can now listen from all these points and see if you can hear air escaping. An automotive stethoscope is handy.

Air whistling out of the intake probably means a leak around the intake valve.

Air coming out of the exhaust indicates an exhaust valve leak.

If you hear it whistle out of the PCV valve, oil pour hole or dipstick is a sign of that air getting past the piston rings - worn or broken rings.

And if any air bubbles appear in the coolant, it indicates a head gasket leak

This is not an end all be all, but it will help eliminate possibilities. Some leaks don't show up cold.

Since 8 and 6 are next to each other, I would suspect a blown head gasket between the two. I just compression tested mine, for reference:
2 = 188 1 = 155
4 = 170 3 = 178
6 = 126 5 = 168
8 = 170 7 = 175

So you can see on mine #6 is pretty weak, followed by #1. I did #6 3 times, getting 115, 128, 135 so I averaged it at 126. The pressure increased, so I think it is a lifter. I will know more when I remove the valve covers and watch things move as I crank the engine. I was just planning on plugs and wires, but now I am into injector cleaning and VC gaskets.

Very interesting. Are the other numbers within range of each other beyond #6 and #4?

The other thing was that when i added oil to each cylinder the numbers all increased, does this mean that the piston rings are leaking?

Bcurtman: I don’t have the are to spark plug adapter, but I do have a leak down tester coming Wednesday, will that allow me to do the same tests? I’ve never causally used one yet.

Thanks so far guys :)

Wow, oil made a difference! I should do a wet test tomorrow.
There is too large a psi difference between 4 & 6 for a bad gasket. Now I am thinking valve train also. Camshaft, lifter, rockers, valves. That's where the leakdown will show the problem. Do you have a lot of oil in your throttle body from the pcv?

Quote:

Originally Posted by Lisa Bunch (Post 684086)

thanks for the input! I’m looking forward to seeing what the leak down tests shows with the covers off.

there actually wasn’t much oil at all in the throttle body to be honest.

The oil does indicate some ring leakage, but that is fairly normal. The low pressures on 4 and 6 (adjacent) would suggest a blown gasket between the two, which is not uncommon. You are on the right path with the leakdown test. Normally when you have the blown hg between cylinders you get a misfire code on both, in this case I would expect to see an 0306 and 0304. Good luck!
https://cimg8.ibsrv.net/gimg/landrov...8dd7b60e4d.jpg

Wow that’s quite the blown gasket. I was only able to run the truck for a few seconds because the owner apparently let his brother cut the cats out and it is beyond loud to run.

I did start it briefly though, and the check engine light was flashing as it ran. It was hard to hear anything specific given the noise from the open exhaust, but I did give the engine a listen the best I could and I didn’t notice any particularly odd sounds.

for the leak down down test am I right to assume that I should have the valve covers off?

As far as the piston oil leak goes, is it a problem? What effects does it have on the truck?

Thank you

I am you tubing this right now. I don't know if the harmonic balancer has timing/TDC marks, if not, I will have to mark them on mine, then yes, valve covers off to verify tdc and both valve closed. My thumb is too small to feel compression in the cylinder as it comes on compression, though I could get a whistle or something...Shucks, if that's the case, I may as well change the valve seals at the same time...my engine isn't perfect, but it should suffice for a few years.

I watched this YouTube on a leakdown test. I learned some things.