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Bad valve seals or valve guides??? Still fighting this damn car!!!

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newlitemotorist

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Discussion starter · #1 ·
Hey guys,

I have been fretting with this damn car for some time now. I have replaced everything leading up to the manifold that could leak. Well, tonight after I put my leak free throttle body on I hooked the pressure tester up the the throttle body inlet for a quick test. Pumped it up to 25psi and the pressure droped to 10 psi with in 2-3 seconds and then continues to drop off after 10psi but slower.

Knowing that this wasnt good I went out to listen while i pumped up the intake and I could hear air escaping from under the vavle cover. I pulled the valve cover off and I can deffinitly hear air escaping form the valves. I tried moving the piston placement around to see if that changed anything but it didnt. When I took my old turbo off....I could see that oil had leaked down the valves of the center two cylinders and there was oil on the manifold itself. Also, every once in a while I would see a little puff of smoke comming out of the valve cover vent on the side. Through all of this I have concluded that either the valves seals are bad or the valve guides are bad. The motor only has about 900-1000 miles on a fresh rebuild but the motor has sat for almost 2 years because the kid I bought if off of started having problems with boost leaks and he could not figure it out.

I am thinking that with a fresh rebuild i immagine the valve seals were put on wrong.....just hoping the guides are ok.

So you guys think this sounds like bad valve seals and would this cause the car to cut out bad at around 10 psi??? Also, how hard is it to change the valve seals? I figured I would need a special valve spring compresser and with that I could do it with the head still on.

Hope you guys can help.....I just wanted someone elses oppinion.

thanks
 
#2 ·
The valve seals are not designed to hold positive pressure as per my understanding. Also bringing the piston to different positions will have no effect because the pressure is coming from the intake manifold not the cylinder as in a leakdown test. Typically the only side effect of leaking valve seals is smoking, no major power loss.

If you are set on changing them though, they can be done with the head still on the car. You will need to pressurize the cylinder and remove the springs with an overhead spring compressor. Search around it has been discussed somewhere because I do remember reading it.
 
Discussion starter · #3 ·
So do you think I need to perform a leakdown test or something like that??? I can hear the air escaping from right where the valves are so I just figured it was the valve seals.

It just confuses me that I can hear air comming from that end of the head. If I had bad rings wouldnt I hear the pressure release from the oil ports???

It does have an oil leak so maybe the guy ran low on oil for a while and fried the rings....I hope this did not happen but if so atleast it is not a very expensive fix.

I just really didnt want to tear the head off but if its a must to get this car running right I will.
 
Discussion starter · #4 ·
Hey guys,

I did a compression test today and it read 155 across the board cold so I am assuming that the piston rings are ok. What would cause the pressure to release so fast when I pump the intake up???

I thought it was the valve seals but it make sence that they are not supposed to hold any kind of pressure.....so if I have good compression what could be casusing this??? Im really confused right now as I dont know what the heck is wrong with this thing. Do you think it could be the valve guides and would this still allow for good compression???

Please guys....someone lend a hand.
 
#5 ·
quazz209 said:
Typically the only side effect of leaking valve seals is smoking, no major power loss.
Click to expand...
Oil consumption, fouled plugs, decreased knock threshold, & rough starting, increased coking on valves and bad sealing...

To name a few.
;)
 
Discussion starter · #6 ·
Asmodeus said:
Oil consumption, fouled plugs, decreased knock threshold, & rough starting, increased coking on valves and bad sealing...

To name a few.
;)
Click to expand...
So do you know or have an idea what I am dealing with??? I do have rough starting and the car will only run half decent if I cover the lower half of the mass air sensor and even then it cuts out at about 10psi because what ever is leaking becomes too great and things go all outa wack.

Valve seals??? There is no oil in my coolant and there is no coolant in my oil and my compression is good so my rings and my headgasket are ok. The only thing I can think of is the valve guides or the seals.......I can hear the leak coming from the general area of the valves on the head.

Do you recommend a head rebuild or just seals for now???

Thanks for any and all help guys!!!
 
#8 ·
newlitemotorist said:
Am I on my own on this??? I need help guys....I suppose I could post in the help forums but I just wanted to try here first.
Click to expand...
if the motor sat for 2 years and the head doesn't have bronze guides... the guides probably got whiped out the first time you started it. they'll rust and the valves will tear them up on startup. you may want to mic the valves too, though they're not likely to have worn on the stems.

if the guides are bad enough, the car will smoke like a chimney all the time, not just at start up and pull outs like with valve seals.
 
#9 ·
i believe i have experienced the same issue with my setup, my main concern was with blowby in the block however, my compression test dry ran about the same numbers as yours, my suggestion to you is to perform the leak down test and as per the results pull the head, thats all you can really do, good luck :)
 
Discussion starter · #10 ·
RapedApe said:
if the motor sat for 2 years and the head doesn't have bronze guides... the guides probably got whiped out the first time you started it. they'll rust and the valves will tear them up on startup. you may want to mic the valves too, though they're not likely to have worn on the stems.

if the guides are bad enough, the car will smoke like a chimney all the time, not just at start up and pull outs like with valve seals.
Click to expand...
The guides are bronze!!! And the car never smokes at idle....just at startup but it was cold and wet the last time i started it.

I know now that the pressure is escaping down into the crank case from futher testing today but my compression test still baffels me. Today i did another test only this time I was looking at the guage instead of my friend. Every cylinder from the very first stroke hit mid to high 150's except for cylinder 3 with hit 148psi yet all while cold as I cannot start the engine right now. All a wet test did was raise the compression of each cylinder almost exactly 10psi and that is it.
 
Discussion starter · #12 ·
Well I did have the boost tester hooked up to throttle body and not the turbo so i know it is not leaking into the pan that way. When I have pressure in the intake I can hear the air comming from the crank case so this would mean it is leaking past the rings I think....although I have good compression so right now i am confused.

It might be as simple as a bad connection on the mass air sensor:confused:
 
#14 ·
Asmodeus said:
Oil consumption, fouled plugs, decreased knock threshold, & rough starting, increased coking on valves and bad sealing...

To name a few.
;)
Click to expand...
In my experience I have never witnessed power loss like he is experiencing due to leaking valve seals. Im not saying the car will run at 100% but they usually run "ok" after startup.
 
Discussion starter · #15 ·
quazz209 said:
In my experience I have never witnessed power loss like he is experiencing due to leaking valve seals. Im not saying the car will run at 100% but they usually run "ok" after startup.
Click to expand...
I hate this but the more I think about it there has got to be something wrong with either my pistons, my rings, or something. I have performed a compression test and things tested out ok but i performed another boost leak test at the throttle body and I stuck a hose down one of the oil return holes and I can clearly hear the pressure escaping down into the crank case......it has to be passing the pistons some how. I can not get access to a leakdown tester so what should I do??? Re-ring the thing and see what happens?

Thanks for the help guys
 
#16 ·
Well how about the leakdown test first?

Did you say it's been rebuilt?

Aside from the leaking issue, have you inspected your ECU lately?

It's possible whoever rebuilt it didn't know what they were doing. I mean after a fresh rebuild, he just gives up because of a boost leak? Sounds kinda odd to me. With that much money and/or time in the car, I sure wouldn't let a "boost leak" stop me from moving forward...
 
Discussion starter · #18 ·
Alright guys, I have the answers.....and I have more ?'s.

I put the intake and the exhaust back on and plugged everything back in today so I could do a compression test and a leakdown test....(bought the leakdown tester at harbor freight for 39.99). I warmed the engine up and I performed the compression test first. Here is what I got:
cylinder #1: 152
#2: 152
#3: 147
#4: 155

Now the bad. The leak down test showed that I have moderate to high leak down in all cylinders. So some how I have good compression but the rings are still worn??? The air was escaping into the crankcase because when I held my fingers on the valve cover vents and then let off on one of them I could feel and hear the air whoosh out. This would explain my power loss problem as I just had these vents venting to the atmosphere. I think that if i hook hoses up to both vents and recirculate the air back into the intake after the mass the car should atleast run better.

So what do you guys say....new piston rings or something else???
Either way this sucks!!! Thanks for all the help.
 
#19 ·
Air is going to get past the pistons. The rings have a certain amount of end gap and air will pass through. This does not mean that your not getting excessive leak down, but with those compression numbers the rings are probably ok.
 
Discussion starter · #20 ·
bsmart82 said:
Air is going to get past the pistons. The rings have a certain amount of end gap and air will pass through. This does not mean that your not getting excessive leak down, but with those compression numbers the rings are probably ok.
Click to expand...
I know some will pass but my motor will not hold pressure for more than 20-30 seconds total! I read somewhere that is should hold for a few minutes. Anyone else have a suggestion. I want to fix this car but I do not want to play the dsmer "fix what doesnt fix till the problem is fixed" game.

Thanks for the help guys.
 
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