I completed my Eco swap in 00' Cav. I drove the car everything was fine, The car started to leak oil from the bak of the engine where the trans bolts. I pulled the trans and chnaged the rear seal. put it back together and still leaked. Pulled apart again replaced the seal reinstalled, Still leaking, Did this 2 more times and each time the car does not leak until I drive it. I can run it at idle with the or without the trans in and no leaks, drive it starts leaking. each time the leak gets worse. any ideas. I have put seal er on the threads of the bolts but I'm thinking its not working.

Maybe a dumb question but if you're sure its the real main seal, have you checked out your pcv system to make sure its operating properly? It needs to be run to vacuum or it won't work. Could be the reason you're blowing a seal..


"In Oldskool we trust"

Yes I checked it. Its working fine. Im not sure its the rear seal. I think its the bolts... wondering if I'm using the wrong sealant or something else...

Are you sure it is oil and not tranny fluid getting dark from dirt.



FU Tuning

Positive... no question about it...

i would wonder if you have bad rings losing compression/excessive crankcase pressure... does it run well? as in good compression, no spit/sputter loss of power? if you are sure the leak is coming from the rear seal then there is a reason it keeps coming from there, is the seal damaged when you remove it? or does it physically look blown out from pressure?


Have a nice day.

I'm positive its not coming from the rear seal. Each seal I have taken shows no wear and installed correctly. The leak is between the fly wheel and block as there is a ton of oil there and not in the bell housing or on the clutch. I think its the bolts. I wondering if there is an issue with the sealant I used or the bolts themselves. I have no loss of power and great compression. It passes the PCV test as outlined in GM repair procedures. Again I can run the engine for over an hour without the transmission installed and get leaks. I can the engine with the trans installed at idle and get no leaks. Once I engauge the clutch it starts leaking.

Could it be the pan gasket? You would think the source of the leak would be easy to find... what bolts do you think are leaking? I didnt think any of them would go all the way to the crankcase or anything like that.. never have i ever put any sealant on any bolts for that purpose.


Have a nice day.

Input shaft seal on the trans?

Are you talking about the flywheel bolts or the trans bolts? There should be any fluid behind the flywheel bolts. There also shouldnt be any fluid behind the trans bolts to the engine block. Either way a leak from an unsealed bolt wouldnt be massive. You would just see some liquid seeping under the heads. If it doesnt start leaking until the transmission is in, its probably in the trans.

How fast does the oil level drop in the engine?

fast enough to just about empty the crank case of oil. The fly wheel bolts is where i think its leakinf, they bolt completely through the crank. I resealed the oil pan. The onlt thing i can think of are the flywheel bolts. It onlt starts laking after the clutch is enagned, will run for ever with the trans in and not leak enage the clutch pours out. that cant be the oil pan.

Where is this PCV test from GM might I ask? I fsomeone could om me the place to find?

The test is in a GM repair book.the dealers would use:
CRANKCASE VENTILATION SYSTEM Inspection/Diagnosis
I copied exactly what is written in this section.

1. Disconnect the PVC hose
2. Start Engine
3. Check for vacuum at the hose or manifold port. Check for a hose that collapses when blocked (Vacuum applied). Replace the plugged or Deteriorated hoses.
4. Allow the engine to idle at normal operting tempature.
5. Remove the engine oil dipstick and install a vacuum gage on the dipstick tube.
6. Block off the PCV system fresh air intake passage.
7. Run the engine at 1500 RPM for 30 seconds, then read the the vacuum gage while engine is running at 1500 RPM.
* If vacuum is presnt, this indicates that the crankcase ventilation system is functioning properly.
* If no vcuum is indicated, the engine may not be sealed and is drawing in outside air. Check the valve covers, the oil pan gasket or other sealing area for leaks.
* If the vacuum gage registers a pressure, or if a vacuum gage is pushed out of the dip stick tube, check for a plugged PCV port, a plugged hose or an excessive engine blow-by.

Neat,

I actually made a fitting to go in the oil dipstick tube with a vacuum guage, basically does the same thing.

So can any one tell me what would cause excessive pressure in the crank case. I have replaced to many rear main seals, and this is the last thing I can think of. I changed the flywheel bolts. because I thought it was leaking there, but thats not it.

Excessive crank case pressure? Assuming your vent system is working probably scored piston/cylinder


Have a nice day.

I followed GM procedure to check the PCV system that worked as described. I change the rear seal put the car back together, I let idle for 30 minutes no leaks. I drive aroun the block no leaks, I take on the main road, andI smell the burning oil. Pull over and its pouring out. I put a new seal in this morning drove and it blew the out. Its pushing the rear seal into the flywheel.

I would lean towards a scored cylinder then. I dont recall if you Did it or not but do compression/leakdown tests on all 4 cylinders. Will probably show one or more of them low/leaking down


Have a nice day.

I have done this and all the cyclinders are maintaining compression, and all showed about the same compression... Thank You

Add oil dye to the engine the get it to leak, then use a uv light to pinpoint the leak exactly

Thx but the exact leak is the rear main seal.

I did a compression test from left to right, 100, 90, 100, 100.
I placed a vacuum gauge on the oil dip stick tube and blok the PVC port as dirtected, the gauge read 10 Inch HG the rear main seal came out at 5-6 inch hg.
Any Ideas. Im thinking maybe theres a problem in the rings causing some pressure in the crankcase.

maybe its time to get another engine, eco's can be picked up for around $500..

Although the compression numbers are all within a safe range of each other, I'm almost positive they are low since no piston should be under 100psi and when I tested mine it was around 160psi (IIRC)

Dan McClure wrote:Thx but the exact leak is the rear main seal.

I did a compression test from left to right, 100, 90, 100, 100.
I placed a vacuum gauge on the oil dip stick tube and blok the PVC port as dirtected, the gauge read 10 Inch HG the rear main seal came out at 5-6 inch hg.
Any Ideas. Im thinking maybe theres a problem in the rings causing some pressure in the crankcase.

Something isnt right...you should be up in the 180 range per cylinder.

Do a leak down test and pull your dipstick when doing it.

Yep agreed

Leak down has air coming out of the dip stick tube and the torn rear seal. Think the rings are bad...