'97 Lt1 in my firebird.....

about 4K on a rebuild, it has been leaking oil since the day it was started. It has completely soaked the underside, and rear bumper of the car. The oil is all over the starter, bellhousing and trans.

So far I have replaced
-Oil Pan Gasket, oil pan is not bent or warped.
-Rear Main seal, and rear main housing to block gasket.
-Intake Manifold Gasket, with dimpled block and RTV on the front/rear
-pulled the oil pressure sender on top of the block behind the intake, reassembled with plenty of thread sealant.
- Not coming from the oil filter or its gasket.


What else is there? I can feel the block and top of the bellhousing wet when I reach back there.....

 

Valvecovers can cause that as well. Stupid but it even happened to me. I ended up using adhesive so they seal to the gasket for sure and then recheck them after a few heat cycles. Never had it happen to me before on other engines or setups.

You are stating it is on the bellhousing. How high up would you say. It could possibly be that your intake is not seating properly to the heads or block. Are the heads or intake milled at all or stock?

There is a plug that goes above the oil filter that is blocked on 94-97 cars, this is where my oil pressure sensor is on my 93, make sure your plug is tight.

Do you have an oil cooler?

Would not expect the rear main since you stated it is on the bellhousing. Just trying to think of all possibilities. I know it is a pain to track down once everything is coated.

Dip stick can also cause a leak but it is not that common. Mine is even cut short and it does not leak.

 

pull the dipstick out and put some silicone on it and stick it back in, betcha that fixes u up, make sure and clean the block and dipstick with carb cleaner to get all the oil off so the silicone will stick...only other thing that u didn't list is valve cover gaskets.

Good luck

 

I know on the Gen I blocks there is an oil plug on the deck of the engine block. It is half covered by the driver side cylinder head. This plug is on rear portion of the engine. Maybe ours has it too. You could also see if the oil plugs on the rear of the block around the Cam are leaking.

 

I forgot to mention that I double checked these as well, and they are good.


I will check out the valvecovers and dipstick tomorrow....thanks for the ideas fella's

 

Is your timing chain cover oil free? One of the most common oil leaks is the waterpump gear seal in the timing chain cover.

 

Yes it is, CSI pump as well....

 

Where new freeze plugs put in during the rebuild? Where they sealed properly?

Seems as though if you have oil on the back of the block and on top of the bell housing, the intake must STILL be leaking. If you have to seal the front and rear surface, use ultra black from permatex.

 

I had a SBC 350 develop a similar leak once. Couldn't track it down for a while. Ended up being the dip stick tube, where it goes into the block. Pulled it out, new O-ring and a little RTV fixed it up.

Thomas.

 

Yup... what ^^^^ said. Common once the tube has been rmoved and re-installed on LT-1s.

 

I'll check this out as well, is there supposed to be an o-ring?

I did look at the freeze plugs when I had the trans out to do the rear main, and they were clean and dry.

I used copperseal on the intake manifold, does permatex black work better?

 

For me it was the seal around the water pump shaft, it has a double lip and if it gets put on wrong and the inside lip is damaged it will leak like crazy. If thats it make sure you get a took to put that on, you can't just jam it onto the shaft. I used a socket wrench that was .0005 bigger then the acutal water pump shaft, ground it down to a slight angle, put the seal on that and then after the timing cover was on just put the socket wrench against the pump shaft and slipped it off the socket and onto the shaft....oil leak solved (for me at least).

Now I have a new leak...somewhere.

 

This may be a little bit of a pain, but try to clean everything off with a brake cleaner or other type of cleaner and then go to an auto parts place and get some dye that pours into your oil fill (most places sell this stuff with a little black light, too)...Run the car for a few and then crawl around under the car with the black light...The dye will show up with the black light( the stuff I used turned orange) and you should be able to see where its coming from...

--Alan

 

Hard to understand since SBC's don't use an O-ring at the dipstick. And the crankcase is under vacuum unless the PCV system is screwed up. Nor do I see how if it did leak, for the oil to get on the top of the bell housing from down where the dipstick goes into the block.

I would only use Permatex Ultra Black on the intake. I don't see any reason/advantage to use something with copper in it. BTW, many intake gasket sets come with those cork end gaskets and they aint worth a S@#T. Do yourself a favor and use the black and try not to move the intake around much after you set it STRAIGHT down on the engine.

Do as ABA said. Put a dye in the oil and look for it with a light. I know UV light is necessary but I don't know if a black light uses UV or not. Or where to get a black light. The UV flashlights are available at most auto parts stores as well as the dye.
Like this one. http://www.lislecorp.com/tool_detail.cfm?detail=585

 

The LT1's were famous for intake leaks at the back of the engine. It run run down either side of the bell housing. The problem was the EGR tube was sometimes too close to the reat of the engine and the seal at the back of the intake could not withstand the excessive heat generated from the EGR tube. I had a '94 Z with the same problem.

Here is how I fixed mine. I bent the EGR tube away from the back of the engine toward the firewall several inches. Wrapped the tube with some heat tape used on race car headers (for extra insurance). Replaced the intake gasket, letting the sealant cure for 24 hours before starting the engine. I never had another problem again.

*Note: It is a PITA to replace the gasket due to the limited access.