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Discussion Starter #1
I'm looking at buying a TT Supra (94) and I just got back the compression test results. They were performed by a Toyota Dealership. The results are as follows:
Cylinder PSI
1 160
2 180
3 185
4 180
5 165
6 185

Turbo tested at 11 PSI which seems right. From what I got from the Supra manual, the cylinders should be around 158 PSI with the variance between the cylinders not being more than 14 PSI. My questiosn are:
1) The maximum varinace between cylinders is 25 PSI (185-160)...10 PSI above the max. From what I can see, this is not good and would require a rebuild.
2) Do the 2,3,4,6 cylinders have too much pressure or is 1 and 3 too low? Would the higher PSI damage the engine in any way?
3) Would a rebuilt be able to fix the higher pressure\cylinder variance and bring them in line with the specs.
4) Could the higher PSI do irreparable damge to the engine cause premature wear?
5) Should I get any other tests done?
5) Finally, should I buy the car and get the guy to reduce the cost by the average cost of a rebuild or should I walk away? I am willing to do a rebuild down the line, but I just want to make sure that the main engine parts are not being damaged i.e piston, ealls, etc.

Any help would be greatly appreciated.
 

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180 psi seems very high. Are you sure they did the test when the engine was at normal operating temperature? This is very important, because the results will be different.
 
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Discussion Starter #3
I jsut talked to service guy. He said that they ran it dry... don't think they warmed it up properly. He said the more PSI the better, and that the difference between the cylinders is normal. and nothing to worry about. Once I gave him the specs from the Supra repair manual, he said he would check it out on the computer (DTS). COmputer was down so he talked to some of the mechanics. He just phone me back now and said that the difference between the cylinders was prob due to carbon deposits and that an engine cleaning should fix it. I don't have too much faith in these guys.

I think I should get it checked out by another dealer and make sure they do the test properly. If it still comes out high and with the variance, does that mean a rebuild?
 

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Shawn Davis
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I'd be concerned about the difference.

I've got 156k miles on my engine and the difference is still within 5psi. Shouldn't the carbon buildup be roughly even across the board.

When I looked at my first supra I had the compression test done and the mechanic tried to convince me that the readings were fine despite a 20 psi variation and generally low readings. I told them the spec and the mechanic said that since the engine was turbo it had lower compression than other engines. I explained that the spec I quoted was for the turbo engine and all he could say was..."oh, well I'm sure its fine..."


:rolleyes:
 
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Discussion Starter #5
Yeah, I'm concerned with the difference.

The car only has 65k miles on it so I don't think carbon buildup would be that big of an issue. I got the same "it should be fine" response when I gave them the specs. Seems like they really didn't care. Either the results are messed up or the engine isn't under specs. If the engine is bad, I would have to pass on it unless they pay for a rebuild .... thanks for the input... for a while I thought maybe I was wrong. I'm up in Canada where Supras are superhard to find. I was hoping this would be the one (my first one that I'm looking at) but maybe not .... I guess the worst thing is to rush into it.
 
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Discussion Starter #6
I would take the car to at least one more mechanic to get another test done. This time make sure who ever does the compression check warms the engine up first. Dont assume the engine is bad because of one compression test done by a grease monkey who dosent give a rats ass.
 

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Shawn Davis
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If the rest of the car is great another compression test might be order.

I think a cool engine would lead to low numbers across the board and not change the difference. Just like if you ran the test with the throttle closed (technically you're supposed to pull the throttle body for the test.)
 

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Ubermensch said:
I think a cool engine would lead to low numbers across the board and not change the difference. Just like if you ran the test with the throttle closed (technically you're supposed to pull the throttle body for the test.)
You don't "pull" the throttle body. You just need to make sure the throttle plate is open. You can do this with your foot each time you test a new cylinder.

Many engines have more variation between cylinders cold than hot. My numbers vary ~6psi cold, but less than 2psi hot.
 

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Yeah, I believe the consensus here is to get the test done by somebody that knows what they are doing. You shouldn't have to explain to your shop how the test is conducted. They're obviously not competent. I'm sure the numbers will be more in line once the car is warmed up.
 
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Discussion Starter #10
OK ... I got another compression test done ... i talked to the mechanic who did the first one, he said that the results were done when the engine was warm. ANyways, here are the new results:

Cyl PSI
1 170
2 170
3 175
4 170
5 170
6 180

Compare this to the old results of (1>6): 160,180,185,180,165,185

This is a Twin Turbo ... so are these numbers too high? If they are high, what are the negatives i.e. engine wear/damage? I will prob get it checked out in one more place before I buy it. I'm also wondering if the change in results is reasonable or is the mechanic making up numbers?

If these are the real numbers should I get the car?

Thanks for the help.
 

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Shawn Davis
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Lagtime said:


You don't "pull" the throttle body. You just need to make sure the throttle plate is open. You can do this with your foot each time you test a new cylinder.

Many engines have more variation between cylinders cold than hot. My numbers vary ~6psi cold, but less than 2psi hot.
As I said its fine to do the test with the throttle just open, but the service manual says to remove the throttle body prior to the test.

That's an interesting second point. I stand corrected. I've never heard of that before, but that doesn't mean its not the case.


Blackdog,
I think its strange that a shop you had to tell the spec to suddenly finds themselves within it after an initially low test.
 
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Discussion Starter #12
My thoughts exactly. I'm phoning around today to see if I can find a service shop who has experience with Supras. That way he can look at the whole car and give me some expert advice since he'll know what to look for and do the tst right. The car I want to buy is an hour out of town for me so that's why it's a little inconvenient and there isn't much choice out there, but, I might have to get the guy to bring it into my city if I find someone here, which shouldn't be a problem.

Just out of curiosity, if those were the correct numbers, what would they do to the engine over itme i.e. overheating, knocking? Still learning about cars so, just wondering .... Thanks
 

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Ubermensch said:


As I said its fine to do the test with the throttle just open, but the service manual says to remove the throttle body prior to the test.

The manual says to remove the TB for the NA engine, the 2JZ-GE. Try to be reading the correct paragraph if you are offering advice. :)
 

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185 is not an umcommen reading. I have dont the test on a few of them. My highest was 175 and my lowest was 144 if i recall and that was at about 100K miles. I now have 127K and it still drives like day one, only faster. 80)

I let the engine getup to operating temp then I perform the test.
 
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Discussion Starter #15
Those compression numbers look pretty good. With 170-180 psi across all of the cylinders I bet that engine is making very decent HP.
but definetely get a dp and exhaust on that car to relieve any back pressure.
 
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