Leakdown test and TDC location
09-13-15, 06:40 PM
#2
So i'm a little dumbfounded- is TDC always at the very top? It seems like what I thought was TDC on the even cylinders wasn't. Is TDC not at the very top for 2, 4, and 6? Are there actually 2 different times when the cylinder is on top, and only one of them has all valves shut?
I'd like to know for sure what the deal is here. I'm assuming since I managed to turn the crank a bit and get to a position where it held 98% of its air, that this means there are no leaks and the engine is good to go. Thanks.
09-14-15, 03:22 AM
#6
Maybe you are not just on TDC . At the same time , when you say "Screwdriver being on the highest point" , that is the TDC , when both intake and exhaust valve are fully closed.
Timing might not be set right or It could be you have a timing belt or cam /timing gears with worn teeth . Seldom , especially for an old engine to have a 0 (Zero) percent leakage in every cylinder... almost in my opinion , only a few you will find with perfectly zero leakage. In fact I have never seen one.
On the contrary , I have seen tons of 2jz/1jz have miserable leakdown numbers or let us say fail the normal leakage expected which 0-10% in every cylinder. They will still run but don't expect it to run optimally especially if it is a boosted car.
Will that leakdown tester be able to accept 100psi ? IMHO , much better to have that amount of pressure testing for leakdown. It gives you better or more accurate status of leakdown , just my $0.02.
That figure you mentioned of holding 8psi means you have over 75% leakage on that cylinder since it is only holding less than 25% of the 40psi you introduced. Try introducing 100psi if that tester could hold it.
Timing might not be set right or It could be you have a timing belt or cam /timing gears with worn teeth . Seldom , especially for an old engine to have a 0 (Zero) percent leakage in every cylinder... almost in my opinion , only a few you will find with perfectly zero leakage. In fact I have never seen one.
On the contrary , I have seen tons of 2jz/1jz have miserable leakdown numbers or let us say fail the normal leakage expected which 0-10% in every cylinder. They will still run but don't expect it to run optimally especially if it is a boosted car.
Will that leakdown tester be able to accept 100psi ? IMHO , much better to have that amount of pressure testing for leakdown. It gives you better or more accurate status of leakdown , just my $0.02.
That figure you mentioned of holding 8psi means you have over 75% leakage on that cylinder since it is only holding less than 25% of the 40psi you introduced. Try introducing 100psi if that tester could hold it.
Last edited by gerrb; 09-14-15 at 03:28 AM.