Well what a bad day , I have an excessive amount of oil blow by coming from the dip stick and the PCV valve on my 1990 L98. Also looks like it may be leaking from the rear of the engine. Any thoughts? or ideas where to start?

 

If it were my car, a leakdown test would be my first test.

 

hi pete k,
you mentioned a leak down test, i am looking at buying the otc brand leak down tester guage @ $ 60.00 soon and i was wandering how and what the procedure is to use this guage and what to look for as in time wise/guage specs please when doing this test?
can you please expalin what the procedure is to use it please ?
regards
shae

 

A leakdown tester requires an air compressor.
Basically, 100 psi is put into the cylinder, and the guage will show the psi that the cylinder is holding. If you put 100 psi in, and the guage reads 90 psi, there is 10% leakdown.
The closer to 100 psi, the better. 85-90% is typical on an older engine. Most do not pump better than 5%.
All 8 holes must be tested to properly perform the test.

 

And you can determine the point of leakage by listening at the TB for intake valve leaks, the tail pipe for exhaust valve leaks, and the crankcase breather for ring leaks. Since you are blowing the dipstick out of the tube and are getting blow by at the PCV, we pretty much know that you have a ring seal problem.

RACE ON!!!

 

hi pete and cfi-efi
thanks for the explaination there!
regards
shae

 

That is what I was thinking as well. I guess it's time to research what parts will work best and get started. I may as well do it up proper and get the extra ponies I want at the same time. Or maybe just go to the 383 crate? any suggestions? Thanks for the help

 

How many miles are on this beast anyhow?
IMHO
first of all,
1. determine that your pcv valve isn't gunked up and is still working.
2. verify that your vent hose is in good shape, and is hooked up
3. verify that the tube on the throttle body that the crankcase vent is hooked to is free and clear.
3A. check that there is vacuum at the vent tube on the throttle body with the throttle plates open and closed.
3B. pull the vent tube off the throttle body, and hold it so you can see if there appears to be oil smoke coming out. The PVC valve should be pulling on the crank case from the valve cover, and there should be no smoke. If there is, troubleshoot the pvc system.
THEN
start troubleshooting for a bad set of rings.
personally, if you don't beat on the car, a simple compression test will pin point the bad cylinder.
If you treat it like it was stolen, then the leakdown tester is a good idea. Because when you thrash it again, and it fails to hang together, you will need it again.
4. If you have the sandwiched oil cooler under the oil filter, that o-ring might be out of squish, and is allowing some oil leakage past it.
5. determine that the oil pan drain plug nylon gasket is good.
6. try tightening the oil pan bolts just a little to determine that the gasket is being compressed enough to actually seal the pan.
7. If you take a flashlight and mirror, check the back of the block to see that the intake manifold rear seal is really sealing since it's just a ribbon of gasket sealer.

 

I am almost positive it's a ring problem, I likely washed out the cylinders . I was on the thrittle at the time with 150shot of N20 for about 5-6 seconds . The problem started right after and I have only put about 3 miles on it since the damage was done. I trailered the car home (6 hours) and now she will sit as a winter project. Question is , Should I rebuild it or get get a crate motor?

 

My L98 was blowing oil out the dipstick tube with a 125 shot, but not when I run it without nitrous. I since eliminated the PCV valve and the vent tube and went to open element breathers on each valve cover. I no longer have any oil out the dipstick, and my breathers are staying clean, so far. I think the nitrous caused some excessive blow by, the higher cylinder pressures will cause more blow by even on a new engine. The L98 pcv system, in my experience, is hardly big enough to keep up with a stock motor. I'd try breathers before I'd rebuild if I were you. For the price, it would be worth it even if it were a bandaid till the winter rebuild.

 

If I were you
1. Pull all the sparklers out, and add a squirt of marvel mystery oil to each cylinder. (thin red oil with a great reputation)
2. spin the engine on the starter for about a half a minute, being careful to place rags inline with the spark plug holes to catch what comes flying out.
3. add another squirt, and let it sit for about 5 minutes, then put all the plugs back in.
4. start it up and let it idle or about 15 minutes.
5. drive it like a grandma for about 1000 miles.
Try it, and what do you have to lose? you will just reseat the rings and reestablish the oil barrier in the oil rings and tensioners.
This should help if not cure the problem.

 

Thanks coupeguy, any idea where I can get this mystery oil?

 

great info there, thanks
shae

 

I had an excessive amount of oil blow by, but i had broke 4 of the pistons. lets hope thats not the case, but a rebuild is a rebuild no matter what caused it

i hope the best for you

 

Next week it will come out and I will break it open to see how bad the damage is. Then I need to decide which way to go on the rebuild. Any suggestions are welcomed

 

.....but what did you do to break 4 pistons? Were you spraying at a low rpm?

 

Most auto stores sell it. I saw it at Advance recently.

Jake

 

Not sure if I have 4 pistons out or not I beleive that was another post from another member. Hopefully my sistuation is not as bad.. I have a definate oil blow by so I know the rings are gone on at least one cylinder. I need to do the lead down to confirm. The spay was at 3500rpm to 4500rpm. I could here the detonation and shut it down. Still runs and idles good, just a serious blow by issue that makes it look like a steam engin if the oil fill cap or PCV is out as well it keeps pushing the dip stick out and smoking and sputing oil out of it.

 

Is your shot a wet or dry? I'm running a Zex 125 shot with 6* base timing and I don't hear any detonation. Do you know what caused your detonation? What was your timing set at? I'm a little concerned now that I'll break mine too. As I said above, I have oil blow out the dipstick tube if I use the stock PCV system when I use nitrous but with open breathers I do not. I never have any smoke out the exhaust. I can't afford a rebuild right now so any advice would be appreciated.

Also, if it looks like a steam engine coming out the oil fill hole....are you sure it isn't water and steam getting over into the crankcase somehow? Possibly a head gasket or something? You could possibly check by pulling the oil drain plug and see if you get a little water before any oil comes out. Or maybe pull the oil cap while running and see if there are any water droplets. I could be way off base, but could be worth checking.

 

Going to do a leak down this weekend. but I am sure that the rings are gone. The timing was factory. and i was using 150 wet shot from NOS. I will keep you updated.