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Leak down test
- Thread starter Andyman
- Start date
Clio 200 Cup
Its primarily leakdown rate you are interested in. It's best to use a gauge but you can tell a lot by listening.
Bring the cylinder you want to check up to tdc. Presurise the cylinder by feeding compressed air in via an adaptor screwed into the spark plug hole; and listen to three things:
1) Listen to the end of the exhaust. If the exhaust valves are passing, you'll hear it.
2) Listen to the inlet (take the airbox off). If the inlet valves are passing, you'll hear it.
3) Take the oil filler cap off and get your ear next to the hole. This can be a tricky one but if the piston rings are buggered you'll hear them passing too.
Anything particularly bad will sound louder than the other two.
Just a guide but if you are getting severe leakdown then the above system will tell you what is to blame.
Hope this helps,
Kevin
Much appreciated for the help Kevin. You wouldnt happen to know what the readings should be for a 172?
From what youve said it sounds like a good hours labour there which wouldnt be far off the cost to buy one new?
My mate works in a garage but only has a compression tester which isnt as accurate i believe.
From what youve said it sounds like a good hours labour there which wouldnt be far off the cost to buy one new?
My mate works in a garage but only has a compression tester which isnt as accurate i believe.
Clio 200 Cup
Im not sure of the correct leakdown figures, infact Im not sure leakdown rates are engine-specific. I think you look for similar leakdown behaviour in all 4-stroke engines. I could be wrong on this, so check 
If a compression tester gives good figures then there probably isn't any need to go through the process I described.
Note: Compression test figures are dependant on compression ratio, and are therefore engine-specific.
If the compression test comes back poor then the process I described can tell you whats wrong. For example you might decide the piston rings have gone on No.3 cylinder, etc
The last leakdown tester I used was £300 worth, and again, all this tells you is the leakdown rate. If you find excessive leakdown then its time to start listening for where its leaking - you dont necessarily need something as elaborate as a leakdown tester to do this.
I'd run a compression test (cheap) and then if you identify a bad cylinder do the leakdown checks I descibed using an adaptor (also cheap)
Glad to help,
Kevin
If a compression tester gives good figures then there probably isn't any need to go through the process I described.
Note: Compression test figures are dependant on compression ratio, and are therefore engine-specific.
If the compression test comes back poor then the process I described can tell you whats wrong. For example you might decide the piston rings have gone on No.3 cylinder, etc
The last leakdown tester I used was £300 worth, and again, all this tells you is the leakdown rate. If you find excessive leakdown then its time to start listening for where its leaking - you dont necessarily need something as elaborate as a leakdown tester to do this.
I'd run a compression test (cheap) and then if you identify a bad cylinder do the leakdown checks I descibed using an adaptor (also cheap)
Glad to help,
Kevin
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