Compression Test Failure
#1
Compression Test Failure
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
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
#2
Read the DTC codes
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.
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.
#3
#4
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 '?
Can you give more detail about exactly what happened when the engine 'stopped when we tried to drive it '?
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kansanbrit (08-13-2021)
#6
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 '?
Can you give more detail about exactly what happened when the engine 'stopped when we tried to drive it '?
The engine died as soon as I put it under load.
#7
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#8
#10
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.
#11
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.
You should do your compression test with the throttle fully open ..many people forget this.
Last edited by Pistnbroke; 08-06-2021 at 01:24 AM.
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piper 888 (08-15-2021)
#13
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#16
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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.
#17
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?
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?
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
#18
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.
Also what does the tensioners look like?
Cheers
#19
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
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
wj
#20
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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.
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JimmyL (08-08-2021)