shn7 Posted August 2, 2004 Share Posted August 2, 2004 Title says it all really. How is it done and what form do the results take? Steve. Link to comment Share on other sites More sharing options...
Chelspeed Posted August 2, 2004 Share Posted August 2, 2004 Take the plugs out. Put the cylinder to be tested on TDC to ensure the valves are closed, doesn't need to be exact, don't need a dial gauge on the piston just somewhere close. Then put the air line onto the leak tester set the regulator to give 100% leak down with the tester not connected to the engine. Then connect the tester to the plug hole to be tested, usually theres a screw in pipe with a plug thread on the end and a quick release fitting to attach the tester on the other end. Then read off the %age leak down. The reading is a percentage, presumably the %age of air that isn't being retained by the piston rings valves etc. With the tester I usually borrow a reading in mid single figures is good, ie 5% is OK, a reading of over 10% is indicative of a problem. But as with a compression test it's the cylinder to cylinder comparisons which are most likely to indicate a problem, ie 4, 6, 15, 5 for a problem with rings on no 3 or perhaps 4, 16, 18, 6 for a headgasket problem between 2 and 3 cylinders. Link to comment Share on other sites More sharing options...
shn7 Posted August 2, 2004 Author Share Posted August 2, 2004 Ok, but does that really tell you anything different from a compression test. (pardon my ignorance here) Steve. Link to comment Share on other sites More sharing options...
shn7 Posted August 2, 2004 Author Share Posted August 2, 2004 Also is this something that any local garage can do? (I don't have an airline/compressor). Steve. Link to comment Share on other sites More sharing options...
Gridgway Posted August 2, 2004 Share Posted August 2, 2004 just out of interest, why do you want to do one anyway Steve? Graham Link to comment Share on other sites More sharing options...
shn7 Posted August 2, 2004 Author Share Posted August 2, 2004 'Cos the suggestion from CC about the reason for a cranshaft oil seal failure (resulting from excess crankcse pressure) is a broken piston . So before taking the engine out and replacing the seal (assuming I'm right about it having failed) I want to do any tests necessary to check for a reason for the failure. Steve. Link to comment Share on other sites More sharing options...
Gridgway Posted August 2, 2004 Share Posted August 2, 2004 well that wouldn't be good on a rebuilt engine. Have you done a compression test? Graham Link to comment Share on other sites More sharing options...
shn7 Posted August 3, 2004 Author Share Posted August 3, 2004 Agreed and if a problem is confirmed I shall be speaking to CC about it. If no problem is found then I don't mind doing the seal myself as it sounds straightforward enough. But I'm not getting involved in fixing the internals. As to tests, not yet, but hoping to borrow a comp. tester soon. Steve. Edited by - Steve Newman on 3 Aug 2004 06:43:35 Link to comment Share on other sites More sharing options...
Jason Plato Posted August 3, 2004 Share Posted August 3, 2004 How does valve overlap at TDC affect the leak down test ? Link to comment Share on other sites More sharing options...
Peter Carmichael Posted August 3, 2004 Share Posted August 3, 2004 You put it at the TDC between the compression and firing stroke. Link to comment Share on other sites More sharing options...
Rob Walker Posted August 3, 2004 Share Posted August 3, 2004 It doesn`t Dave all valves are closed on the firing stroke. Edited by - Rob Walker on 3 Aug 2004 08:26:20 Link to comment Share on other sites More sharing options...
AndyA Posted August 3, 2004 Share Posted August 3, 2004 Broken Pistons - the Super & MegaGrads 'had' a problem with pistons in race use, speak to Andy Mc at McMillan Motorsport for one solution. Link to comment Share on other sites More sharing options...
ECR Posted August 3, 2004 Share Posted August 3, 2004 Never having used a leakdown tester and not wishing to buy one (but interested in its design/use)Could a reading be taken with just 2 regular pressure gauges ? If I set the output of my compressor to say 100 psi and then connected it to a cylinder from which another gauge exited (through the adaptor) then if I get 100 psi on the second gauge I have no leakdown, if I get 50 psi I have 50% etc. Have I just described a leakdown tester ? Link to comment Share on other sites More sharing options...
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