Hi All,

My project 99 XKR has just failed a dry composition test, the resulted were:

Righthand
1 = 50 psi
2 = 100 psi
3 = 90 psi
4 = 0 psi

Lefthand
1 = 100 psi
2 = 100 psi
3 = 90 psi
4 = 70 psi

The engine did run but stopped when we tried to drive it which is why I had a compression test run.

Any help or advice would be most appreciated as I'm hoping a new engine or rebuild is not required

Thanks in advance

 

Phil,

Not a lot of car history in your write up, so before you go too far, are there any DTCs through the OBD2 port. Well worth getting that done, before you start thinking about an engine tear down.

For compression tests, my limited experience is that the value spread is what should concern you. Plus you have a big fat zero! Stick a camera down the spark plug hole and you may see piston damage. Again, the only time I saw a zero was when the valves weren’t seated, but that was on a 72 Triumph.

 

Thanks for your post David.

The car has done 97k miles but very little over the past few years, interestingly past MOT history have no advisory's which is amazing considering the cars issues.

I dont have reader, do you know of a half decent budget one?

 

I would double check 1 and 4 on the right and 4 on the left. I've been caught out with low looking numbers which revert to normal on a retest - sometimes it's not obvious if the tester isn't screwed in properly, especially at the back of a longitudinal engine. If they persist, put some engine oil in the cylinder and retest to see if compression returns to rule out borewash.

Can you give more detail about exactly what happened when the engine 'stopped when we tried to drive it '?

 

Try a small amount of oil in each cylinder. If you only had it running for a short time there is a chance of bore wash. Then retest.

 

Thanks for your reply, the test was run on Monday and again today with the results being the same. 😡

The engine died as soon as I put it under load.

 

Could the Nikasil cylinder lining have gone?

 

Very unlikely unless it was severely overheated, in which case you would possibly have had a blown head gasket or dropped valve seat. Failure was originally due to high sulfur fuels, mostly in the american south, ancient history now.

 

foot the floor as long as necessary

you don’t even need to put oil in the bore

 

All of the above advice is valid. 97k on a domestic market car - unless no maintenance and absurd habits - just seems out of the ordinary. Symptoms should have built up over months and many miles. Even if there is no Harbour Freight over there, the $100 for a tube camera will pay for itself. Good luck.

 

You say MOT so I guess you are in UK. You can get a camera to put in the bore for £ 7.51 on e bay item 353538885232 OBD reader is tricky but This one from Amazon works with your phone .£13.99 " . I have 3 that do not work so be warned.

You should do your compression test with the throttle fully open ..many people forget this.

 

Where in the UK are you? You may find a local forum member with diagnostics.

 

It could be blown head gaskets. I would look at the oil and see if there is coolant mixed in. It will give the oil a milky appearance.

If you have bad head gaskets on both sides it would suggest that at some point the engine was over heated and warped.

Good luck

 

Thanks for your advice all, the camera is arriving next week so I'll be able to look inside to get a better idea.

I am from the UK (Surrey) if the head gasket has gone can anyone recommend a decent mechanic?

 

It not going to be a head gasket ...where would all the air go pushed up by the piston to give zero psi ?
best way is cylinder leakage test and listen at the exhaust and inlet to see which its coming out .
I assume you have checked the valve clearances on the bad cylinder?

 

Once the endoscopic camera arrives, have a look in the cylinders displaying low compression. If all appears normal, remove the cam covers and see if the cams are correctly timed and if the secondary timing chain tensioners are the metal-bodied variety. If the engine still has the plastic-bodied secondary tensioners, one may have failed causing valve damage.

 

Thats whats strange about the test results (ran twice) the only thing that could explain a zero compression result is a hole, in my mind anyway.

The cylinder leak test is going to be the next thing to run after I've got some photos inside which fingers crossed look okay.

Thanks

 

Thanks for the advice NBcat but how would I test to see if the cams are correctly timed?

Also what does the tensioners look like?

Cheers

 

a valve stuck open (most likely), a broken rod are two other thoughts

wj

 

Here is a link to the AJ Engine Course, which explains about how to check and correctly set the camshaft timing:

https://www.dropbox.com/s/vqpy3bbjzd...e_168.pdf?dl=0

Pay particular attention to page 74 of the PDF concerning the correct way to set camshaft timing.

In these two photos, one can see the secondary chain tensioners pressing on the chains. Note the metal bodied tensioner in the first photo and the camshaft 'flats' in the second photo that must be aligned when the crankshaft is rotated in a clock direction when viewed from the front of the vehicle. Use a 24mm socket on the crankshaft bolt to rotate the engine. Under no circumstances is the crankshaft to be rotated in an anti clock direction as damage to the main and rod bearings is the result.