Leakdown Test

[NYCHonda]

Anyone here know about doing a leakdown test? Is it hard to do?

[coombsie66]

In what respect? R u checkin cylinder compression? For a leak in the oil system? Water?
For cylinder compression test i believe u just get a special gauge that screws in to the spark plug hole, then crank the engine and compare the values of each cylinder.

[NYCHonda]

Okay, here's the problem on my car that I can't solve. I have a 1997 Honda Prelude. I just did few internal work on the engine. I bore the block slightly bigger to fit in an oversize piston. The piston that I'm using is still an OEM Honda piston but with a higher compression. I also did few other minor engine modifications (camshafts, header,.....).

After I did all that work, the engine still losing a lot of oil. Honda Prelude are known to burn a lot of oil but reasonable amount though. Right now, I'm losing a lot more than normal condition. There's smoke coming out from my muffler whenever I hit the gas at full throttle and it's bluish. The smoke isn't a lot though, just a little. I know bluish smoke means there's a blow by.

I brought it back to the machine shop that did the boring on my engine block. They did a compression test. The result came out normal. All the cylinders compression were normal. I also did a compression test myself using the gauge that you talked about and yea the result came out normal either.

I checked if there is any leaks and I don't see anything at all. Someone told me that it could be the valve seals but all the valves & the seals are brand new. I changed it when I did the internal engine work. I also checked if there's anything wrong with my head gasket and nothing wrong. I never lose any coolant at all.

Currently I'm using Mobil 1 10W-30 synthetic engine oil on it. One of my friend suggested the Redline 10W-40 for my next engine oil change. He said that his Integra Type R used to lose a lot of oil when he was using Mobil 1 oil but now after the Redline, his engine lose a lot less oil than before.

I also heard many people told me to do a leakdown test. Okay, now I don't know what's that leakdown test thing all about. Sorry if it's too long but I just want to be as details as possible so maybe someone here understand my engine problem. Any input & suggestions are appreciated. Thank you.

[zevolv]

you might have oil leaking through the Cylinder Heads on the intake valves, it can happen sometimes.
you need special tools for a leakdown test there's a special gauage assembly and you need an air compressor. then you hook it up to the spark plug hole and listen for leaks and also look for air bubbles in the radiator. If the intake or exhaust you have bad valve seats which I would guess since your burning oil, radiator bubbles means bad head gasket also a possibility for burning oil, PCV or breather bad rings or oil galley.

[NYCHonda]

So I guess I have to take it to a shop for a leakdown test. I don't think I can do it by myself. I also did look for that air bubbles on the radiator and I don't see that either. Any other problem beside those? Thanks for your input.

[zevolv]

I fyou said that it is burning oil in the cylinder and it comes out the exhaust it has to be bad rings,valve seats or guides, or head gasket. the only ways oil can enter the cylinder and if you said the rings are fine take the Head off with a torque wrench (don't be stupid) and look to see if there is any signs of oil on one of the cylinders and look at the valves to see if you can see any buildup or leaks on the intake valves(because the vacuum can pull some oil down with through the guides). I would try that I personally would check the rings for safe measure but I doubt you want to pull your motor and pull the pistons especially if you don't have a second car or the equipment.

[NYCHonda]

Isn't that when the rings are bad, you can tell from the compression result? The compression result is 200-200-210-200.

I just changed all the valve & the valve seals too when I did the internal work which is just about 2 months ago and I only put 1500 miles on it.

[zevolv]

in some cars 210 would be too drastic of a difference which can mean build up on the piston maybe oil or carbon deposits and did you replace the guides and make sure all the valve seats were properly angled and that all the clearances and height were correct. Also is the car N/A? if not oil from the compressor what ever type might some how be getting in the air stream.

[NYCHonda]

Yea, the engine is N/A. The piston I'm using right now is a 11:1 OEM Honda piston. I changed all the valve, seals, & the valve springs.

Is there a way I can check the valve without opening the head? Is there any test that I can do?

[zevolv]

not really since it's more of a visual check even if you changed those parts the valve guides could have been worn down and that would cause the leak the guide is what you slide them through some are removable others aren't and in that case you have to find new valves with a wider valve stem. you might need to insert some spacers under the springs if there is too much end play that's something you can measure if you have the right tools. most of which are expensive and you need to know the many measurements. basically you need a friend who can help you out maybe a shop willing to help also and do all the tests at once. If you had an osciloscope or some other tiny fiber optics camera you can insert through te spark plug holes and look to see if there is any build up that would really help a really good shop should have one.

[NYCHonda]

Oh okay, thanks a lot for your input. I appreciated.

[zevolv]

No problem and good luck

[hotgemini]

Making a leakdown tester is quite simple, you can either do it yourself by gutting an old spark plug or purchase an off-the-shelf item. The advantage of a leak-down test over your traditional cranking compression test is that it allows you to diagnose a wide range of flaws, for instance by slowly rotating the engine with the air supply on, switching it off, and rechecking for any leaks you can identify damage to the bore which would not be noticable with a CCT.

As for your particularly situation, first guess would be poor ring seal, either they haven't bedded in properly or there is something more seriously amiss.

When performing a CCT then engine should be at working temperature, one additional test to try is after taking one set of measurements, try dribbling some oil into the bores and rerunning the CCT, if the compression readings increase it is a sign of poor ring seal as the oil helps act as a sealing agent.

[NYCHonda]

Making a leakdown tester is quite simple, you can either do it yourself by gutting an old spark plug or purchase an off-the-shelf item. The advantage of a leak-down test over your traditional cranking compression test is that it allows you to diagnose a wide range of flaws, for instance by slowly rotating the engine with the air supply on, switching it off, and rechecking for any leaks you can identify damage to the bore which would not be noticable with a CCT.

As for your particularly situation, first guess would be poor ring seal, either they haven't bedded in properly or there is something more seriously amiss.

When performing a CCT then engine should be at working temperature, one additional test to try is after taking one set of measurements, try dribbling some oil into the bores and rerunning the CCT, if the compression readings increase it is a sign of poor ring seal as the oil helps act as a sealing agent.

So I can buy the leakdown test stuff at a local auto parts store? As with the last one you mentioned, I did that and the compression readings didn't increase though.