alright so i spent the better part of this morning searching through all these threads and stuff trying ti find out HOW to do a leakdown test and all i have found is people actually doing them. can anyone explain to me how to do a compression leak down test and what the proper numbers should be? im trying to find out if i have a bad valve seal.

i am having bad oil consumption and am trying to find out the culprit. any other compression style tests that can be done and how?
thanks,
-David

 

You'll need the adapter to screw into the plug hole, make sure the little valve stem core is out, and get the piston to top dead center. Then just connect the air to it and verify how much leak down it has by the gauge reading and of course if the valves aren't seating you'll hear air escaping for either the exhaust or intake. I think that any reading of 15% or higher you might have a problem, but I do not have a manual in front of me so I don't know if that number is correct. With the piston at top dead center though you should not have any leaking from either valve so there would be no leaks at the valve seals. It would tell you if your rings were worn though which could definetly be causing the consumption. Does it smoke at WOT or when you first start it up? A leaky valve seal would smoke primarily on startup where worn rings would smoke primarily at WOT. If the valve guides in your heads are worn you could have some leaky valve seals. Hope this helps some.
Ryan

 

it smokes only sometimes at start up. what im saying is that IF it smokes it is upon ignition and alot of the time it doesnt even smoke then. very random. i just put some oil treatment thats supposed to help seals and stop consumption so maybe that help a little. it doesnt smoke at WOT. how do you get your piston to TDC exact?

 

Hey soon, did you ever try modifing your pcv system like we talked about?

 

The leak down tool should look like this

 

zick, no not yet, i just sent you a PM with pictures and specifics to make sure. ill be ordering the thunderracing breather soon and trying it. 1slowhoe has oil smoke pouring out the hose that goes from pass valve cover ot throttle body when he had busted rings.

wilde, what all do you have to have or do for that? jsut remove the plugs and get it to TDC and how much pressure are you supposed to put in the cylinder, just 35psi? where do you get the adapter so that compressor hose will go into the plug port?

i assume you can rent the whole tool so basically how do you get the piston to TDC?

 

A leak down test is not going to tell you if you have bad seals. It will tell you if your valve seats are whipped. If you have blueish white smoke on start up you need seals... All you have to do is take the springs off and replace them it should only take a good wrench a few hours. The cost for the seals is minimal.

 

Im also starting to notice Blueish/whiteish Smoke on start up at random times. I also have noticed oil in the bottom of my intake manifold, but no oil in my intake tube. Im guessing i need to check compression, and all them kindof things.

2nd gear is also starting to slip on my stock trans.

What fun!!??

 

Smoke only on startup is valve seals....probably about $1.00~$1.25 each.

 

I'm not disagreeing on the fact that bad valve seals will cause a startup smoke issue but I'd like to share some info that will cause the same symptoms.

After putting my basically new engine together (05' block w/ 1500 miles & brand new patriot heads) I started having a very bad oil consumption problem. It would smoke real bad at startup, so I naturally assumed it was bad seals. But I also was doubting this too since the heads are brand new.
So instead of digging into the heads to replace the seals I figure I try a easier route first to troubleshoot this problem.

I noticed that with a catch can in place of the pcv system I was getting some oil into it but it didn't seem like very much compared to what I was going through in a months time (2-3 quarts). So I thought that maybe the oil is getting past the catch can and still getting into the intake. So I went to autozone, picked up a clear inline gas filter and put it after the catch can. As soon as I started the engine, you could see a ton of oil going throught it.
After this I completly removed the pcv system and installed a couple breathers in place. Its been over a month since I've done this and I no longer have the startup smoke nor am I burning anymore oil.

Just my .02