Miata question- Leakdown test

Aged racer

Aged racer

New member
Running my '99 as an SSB car (SM next year). The car felt a little draggy at the last National. Had a guy I trust (experienced in german cars, but, hey, I know him..)

Leakdown tested as follows:
#1 8%
#2 28%
#3 20%
#4 6%

At face value, I have a problem. Assuming this looks like a legit pattern, do I need head work or could this be a ring problem ? (Car uses a quart per race weekend, BTW).

Got the Runoff's coming up- comments/ suggestions are welcomed--

Thks- Steve
 
Originally posted by Aged racer@Aug 16 2005, 01:53 AM
Running my '99 as an SSB car (SM next year). The car felt a little draggy at the last National. Had a guy I trust (experienced in german cars, but, hey, I know him..)

Leakdown tested as follows:
#1  8%
#2  28%
#3  20%
#4  6%

At face value, I have a problem. Assuming this looks like a legit pattern, do I need head work or could this be a ring problem ? (Car uses a quart per race weekend, BTW).

Got the Runoff's coming up- comments/ suggestions are welcomed--

Thks- Steve
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Well you obviously have a problem if the test was done correctly. You need to find out where the leak is from.

Did you listen to see where the air was escaping from? That will tell you if it's intake or exhaust valves or the rings.

What are the compression numbers?
 
We didn't do a compression test. You could feel air escaping through the oil filler cap- sounds like rings ?

Thks
 
Originally posted by Aged racer@Aug 16 2005, 11:27 AM
We didn't do a compression test. You could feel air escaping through the oil filler cap- sounds like rings ?

Thks
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Sounds like rings. Was the car at operating temp when you did the test? I'd still do a compression test, but the numbers don't look too good already.

Ron
 
Originally posted by chumpy36@Aug 16 2005, 02:11 AM
Well you obviously have a problem if the test was done correctly. You need to find out where the leak is from.

Did you listen to see where the air was escaping from? That will tell you if it's intake or exhaust valves or the rings.

What are the compression numbers?
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Well if it's mostly coming from the oil filler cap then yes, it sounds like rings. But you need to make sure it's not coming from the valves also.

I would do a comp test, it's easy. Run them dry first then add a teaspoon of motor oil to each cylinder and run the test again. If it's rings the numbers will get better with the oil.
 
All good advice. However, hearing sounds from the filler cap would not automatically mean rings whereas if you heard it from the dip stick tube...
 
Thanks much for the feedback- another racer has suggested I contact Bob Thornton and get him to look at the engine, which is now the plan.

Like Dirty Harry said, a good man knows his limitations....

Steve
 
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