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Old 11-23-2007, 08:10 PM   #1
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Default Is there an engine doctor in the house?

I'm running a 95 with a modified T25 at around 8PSI - giving 175Hp. This is a race only car. My last race weekend, I started pouring in the oil but not a drop to be found on the floor and I really did not notice anything excessive coming out the exhaust. 2 quarts/race. My downpipe was loose (blue smoke escaping between the turbo and the DP).

Pulled the plugs - all had heavy black carbon build up.
Ran a leakdown. 1 and 2 looked good with only 15% loss. Tested 3 - massive compression loss (no compression). Tested 4 - it was less the 3 but still heavy loss. Kept retesting both and trying to hear where the air was going - nothing from the intake, exhaust tail pipe, oil cap or dip stick, nothing from the radiator, but you could hear it kind of deep inside - very audible. When I tested 3, I did not hear anything escaping from 4 sparkplug hole. I would think it would be a fluke to lose rings from both cylinders at the same time??

I drainind the oil - looked fine. I did notice a some metal grains left in the collection pan (no big pieces just "sand" sized stuff. Refilled with oil and ran for 15 minutes then drained it again -very dark for brand new oil (combustion gases getting into the oil)?

I drained the radiator - perfect.

A friend mentioned that maybe a ring got stuck with deposits and to spray carb cleaner in the cylinder. Did that in both and ran it - still blue smoke releasing around the turbo/dp. My guess is that did not do anything. Looked at the tailpipe and there was a black carbon spray on the floor - not too heavy but very noticeable and there was also some 15 drops of water.

Is it possible to have a head gasket fail without fouling the coolant? My guess is 3 and 4 rings are shot. Could both exhaust valves (3,4) be burnt??Please share your opinion and how I can confirm this leak. Thanks, Jim.
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Old 11-23-2007, 08:27 PM   #2
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carb cleaner probally wont do anything, try to replace a quart of oil with a quart of ATF if you beleive something is stuck. do you have a boost guage, if so what it the vac reading? the vac will tell you everything, compression test will just say what cylinder it is. also pour just a tad of oil in 3 and 4 and re-test them to see if you get a different reading.

Last edited by bryantaylor; 11-23-2007 at 08:27 PM. Reason: added more
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Old 11-23-2007, 09:07 PM   #3
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carb cleaner probally wont do anything, try to replace a quart of oil with a quart of ATF if you beleive something is stuck. do you have a boost guage, if so what it the vac reading? the vac will tell you everything, compression test will just say what cylinder it is. also pour just a tad of oil in 3 and 4 and re-test them to see if you get a different reading.
At idle the vac reads 21. Hit the gas to 5K and release - the vac goes to 0, rebouds to 30 and settles back to 21 at idle. What does this is tell you?
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Old 11-23-2007, 09:28 PM   #4
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at idle is it steady? sounds like the motor is ok. if it was a motor problem, it would have dips or would read really low. going by just the vac, the motor is ok.

how is the power? does it feel like its running ok? could just be turbo seals or like valve stem seals
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Old 11-23-2007, 09:43 PM   #5
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at idle is it steady? sounds like the motor is ok. if it was a motor problem, it would have dips or would read really low. going by just the vac, the motor is ok.

how is the power? does it feel like its running ok? could just be turbo seals or like valve stem seals
It is steady at idle and ran like a champ - 1:24:4 at Roebling Road Raceway, just sucking down oil - blowing smoke - now I can really see it in the garage. I'll check the IC for oil but with all of the air loss in the cylinders - starting to sound like valves?? I'll do the cap of oil in cylinder - if no change then every thing points to the valves?? Are there any other tests to isolate the valves as the issue?
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Old 11-23-2007, 10:21 PM   #6
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It is steady at idle and ran like a champ - 1:24:4 at Roebling Road Raceway, just sucking down oil - blowing smoke - now I can really see it in the garage. I'll check the IC for oil but with all of the air loss in the cylinders - starting to sound like valves?? I'll do the cap of oil in cylinder - if no change then every thing points to the valves?? Are there any other tests to isolate the valves as the issue?
are you positive when you did a leakdown test that all the valves in the cylenders were properly closed (aka TDC)?

The thing is if it were valves or rings, and 2 cylinders had very low compression, the engine would not run well at all. (which you said it is, you said you are getting good times at the track). Check the intake pipeing for oil, it very well could be the turbo.
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Old 11-23-2007, 10:51 PM   #7
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are you positive when you did a leakdown test that all the valves in the cylenders were properly closed (aka TDC)?

The thing is if it were valves or rings, and 2 cylinders had very low compression, the engine would not run well at all. (which you said it is, you said you are getting good times at the track). Check the intake pipeing for oil, it very well could be the turbo.
Thanks - 100% positive I had each cylinder at TDC. I agree with you that it is wierd that I had power but it looks like the compression in 3 and 4 is way off. Going to check the IC piping.
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Old 11-23-2007, 11:03 PM   #8
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Thanks - 100% positive I had each cylinder at TDC. I agree with you that it is wierd that I had power but it looks like the compression in 3 and 4 is way off. Going to check the IC piping.
you know what try this. Do the leakdown test, but put alittle oil in the cylinder before you do the test. If you get good numbers with extra oil, then its the rings.
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Old 11-23-2007, 11:09 PM   #9
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your rings are gone.
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Old 11-23-2007, 11:20 PM   #10
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your rings are gone.
Rule out the Turbo - the pipes are clean and dry. I'll do the oil in the cylinder but I think you know!!

So what is the rule of thumb - rebuild the lower end or buy a Planet Miata special?
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Old 11-23-2007, 11:58 PM   #11
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Rule out the Turbo - the pipes are clean and dry. I'll do the oil in the cylinder but I think you know!!

So what is the rule of thumb - rebuild the lower end or buy a Planet Miata special?

If its just rings, and you know what your doing, just rebuild it youself. Plus, thats a great chance to get some nice connecting rods and pistons so you can run more boos with no worrys
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Old 11-24-2007, 09:03 PM   #12
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i doubt its the rings if the motor is running good and its pulling good steady vac. you sure you did the compression or leakdown test right?
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Old 11-24-2007, 09:41 PM   #13
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i doubt its the rings if the motor is running good and its pulling good steady vac. you sure you did the compression or leakdown test right?
Alright sports fans: Did the "put the cap of oil in the cylinder" test. #3 had only12% loss and held - looks like the rings are gone. Did the same on #4 - still major loss - alot of gurgling - sounds like the exhaust valves. Any second opinions?
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Old 11-24-2007, 10:07 PM   #14
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bad oil consumption + poor leakdown + blue smoke = rings.


probably detonated, 1.8Ls see less ring failures than 1.6Ls.
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Old 11-24-2007, 10:43 PM   #15
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Alright sports fans: Did the "put the cap of oil in the cylinder" test. #3 had only12% loss and held - looks like the rings are gone. Did the same on #4 - still major loss - alot of gurgling - sounds like the exhaust valves. Any second opinions?
how many psi was it before and after the oil? your rings are done. i would pull the head and see if the piston and walls are still usable and go from there
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Old 11-24-2007, 11:52 PM   #16
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bad oil consumption + poor leakdown + blue smoke = rings.


probably detonated, 1.8Ls see less ring failures than 1.6Ls.
B: Just a follow up on the "probably detonated..." I'm running 7-8 PSI, watch the AFR like a hawk (always between 11-13), no temperature issues at all, and I really did not hear any knocking/detonation. If not detonation, what are the other general causes of ring failures (old age, over heating, bad oil..?). Very curious on the issue with the 4 cyl. - almost like a head gasket failure between 3 & 4. #4 still lost all compression with the oil added test. Scratching my head on this as I have been actually very careful trying not to kill the engine.
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Old 11-25-2007, 12:20 AM   #17
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B: Just a follow up on the "probably detonated..." I'm running 7-8 PSI, watch the AFR like a hawk (always between 11-13), no temperature issues at all, and I really did not hear any knocking/detonation. If not detonation, what are the other general causes of ring failures (old age, over heating, bad oil..?). Very curious on the issue with the 4 cyl. - almost like a head gasket failure between 3 & 4. #4 still lost all compression with the oil added test. Scratching my head on this as I have been actually very careful trying not to kill the engine.
Without a dual feed rail, cant the number 4 cylinder acually run lean? That would explain it. Someone correct me if im wrong.
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Old 11-25-2007, 12:55 AM   #18
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Best case scenario is you fubarred the HG, and that will be aparent when you pull the head but even so it means taking the motor out of service for a little while. Yes the #4 has been known to run leaner than the other 3 in alot higher HP cars a 8-9 psi setup is not high enough to warrant the dual feed mod. Age could be a factor as could have silent knock listening is only half the equation to detecting knock your knock sensor or in our case working oil pressure gauge is the other.
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Old 11-25-2007, 09:06 AM   #19
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Best case scenario is you fubarred the HG, and that will be aparent when you pull the head but even so it means taking the motor out of service for a little while. Yes the #4 has been known to run leaner than the other 3 in alot higher HP cars a 8-9 psi setup is not high enough to warrant the dual feed mod. Age could be a factor as could have silent knock listening is only half the equation to detecting knock your knock sensor or in our case working oil pressure gauge is the other.
I have a dual rail feed. I agree, looks like engine pull'n time.

Thanks everyone for the help and insight.

Jim
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Old 03-27-2008, 12:17 AM   #20
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maybe a hole in #4 piston?
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