General compression test

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General compression test

Lets end this and tell you how the garage way is. There is a "dry" and "wet" test. Dry is done at beginning with open throttle and pressure guage. When readings have been done, you put a small teaspoon of oil down each plug hole to do a wet test. This is to test for ring failure. If the guage does not read higher, rings/gasket is leaking. Simple and takes 15 mins to test for compression/leaks.

Andy.
 
Oh to test head gasket, coolant header tank should be pressurised to 6 bar to test head. If it cannot hold pressure, it will show leak. Either a pipe, joint or head gasket. And, if you have a friendly MOT garage, ask him to put his emission sniffer in your header tank to smell the tank for leaks. (y)

Andy
 
sumplug said:
Lets end this and tell you how the garage way is. There is a "dry" and "wet" test. Dry is done at beginning with open throttle and pressure guage. When readings have been done, you put a small teaspoon of oil down each plug hole to do a wet test. This is to test for ring failure. If the guage does not read higher, rings/gasket is leaking. Simple and takes 15 mins to test for compression/leaks.

Andy.

exactly as its says on the back of the gunson tester i got to check the turbo's compression
 
sumplug said:
Lets end this and tell you how the garage way is. There is a "dry" and "wet" test. Dry is done at beginning with open throttle and pressure guage. When readings have been done, you put a small teaspoon of oil down each plug hole to do a wet test. This is to test for ring failure. If the guage does not read higher, rings/gasket is leaking. Simple and takes 15 mins to test for compression/leaks.

Andy.

is that with one plug out or all of them?

oh thanks for the info too (y)
 
99sei said:
is that with one plug out or all of them?

oh thanks for the info too (y)
One plug at a time. Does not matter as other cylinders will not effect the one you are checking.(y)

Andy.
 
it doesnt matter compression wise, but you dont want the other 3 plug holes to suck any dirt in during their intake stroke. that could block an exhaust valve or damage a piston ring. there's probaly all sorts of crap lurking around the plug holes. i usually blast the bits off with my compressor before taking a plug out, just to make sure.
 
Liam said:
Sorry, didn't read all the thread, was too much bickering etc on it but for what it's woth, when doing compression tests I remove one plug at a time, screw in the guage, turnover and record readings, repeat for all cylinders then put a small drop of oil down each bore to remedy and possible sticking pistons rings.

Liam

by bore do you mean the spark plug holes?

now the head is off could i put a drop down the valves? or would people recommend not doing this?

got a pic of my head, dont look in bad nick, anything i should check for whilst its off? how do i check for burnt piston rings and bent valves? (im still learning mechanics so be patient with me :eek: )

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When the head is still attached you drop some oil down the spark plug holes and this goes into the cylinder bores and can unstick a sticky piston.

Liam
 
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