70 GT Rear Main Seal Replacement/additive:

[ameyer]

Good morning:

Can anyone tell me the procedure to replace the rear main seal in my 70 GT? 1.9 engine/4 spd. In some GM cars you can replace the seal without backing out the tranny. Leaks while engine is running. Pint a week.
I don't think this is possible on a manual transmission. Is there any additive that would stop the oil leak? Any forums out there that could explain the procedure.

Great site. Learning something new every day. Thanks to everyone.
Ang

[sawdust]

How bad is the leak? A few drops a week? A quart a year?

Buy a drip pan. Keep an eye on the oil level. Add as needed.

I use STP oil treatment. Motor Honey. Every Oil change 3000 miles.

[RallyBob]

Good morning:

Can anyone tell me the procedure to replace the rear main seal in my 70 GT? 1.9 engine/4 spd. In some GM cars you can replace the seal without backing out the tranny.
I don't think this is possible on a manual transmission. Is there any additive that would stop the oil leak? Any forums out there that could explain the procedure.

Great site. Learning something new every day. Thanks to everyone.
Ang

On the older GM cars with a 'rope seal' you can replace the seal without removing the tranny. Slow and tedious, but possible.

Opels use a one-piece rubber rear main seal. Tranny must be removed, as well as the flywheel.

FWIW, on my old 290,000-mile Nissan (which used to leak from everywhere), switching to 20w-50 'Brad Penn Racing' oil stopped all the leaking, and even dropped the oil burning by 2/3rds.

[ameyer]

On the older GM cars with a 'rope seal' you can replace the seal without removing the tranny. Slow and tedious, but possible.

Opels use a one-piece rubber rear main seal. Tranny must be removed, as well as the flywheel.

FWIW, on my old 290,000-mile Nissan (which used to leak from everywhere), switching to 20w-50 'Brad Penn Racing' oil stopped all the leaking, and even dropped the oil burning by 2/3rds.

Thanks.
Ang

[ameyer]

Thank you.
Ang

[jlthunder]

If this engine was rebuilt, some people forget to put a small dab of gasket sealer on the 5th main bearing(not on the actual bearing surface) but where it meets up with the block which extends outside of the pan. Mine leaked there. I dropped the pan, unbolted the main, put the dabs of sealer there and no more leak.

If this is an unmolested engine, then I would say it is the rear main seal and you have to removed the trans.

Good Luck.

[opelnut10]

If this engine was rebuilt, some people forget to put a small dab of gasket sealer on the 5th main bearing(not on the actual bearing surface) but where it meets up with the block which extends outside of the pan. Mine leaked there. I dropped the pan, unbolted the main, put the dabs of selaer there and no more leak.

If this is an unmolested engine, then I would say it is the rear main seal and you have to removed the trans.

Good Luck.

First I would get under the car with a can of brake clean and clean the oil pan area then run the car and investigate that it is in fact the seal leaking.Check all the oil pan bolts to make sure they are snug. Next inspect around the gasket to make sure it is intact without any gaps. If you are not worried about how it looks, sometimes you can clean the rear of the pan around the seal and smear some high-temp Permatex gasket sealer in that area to help it, if it is the seal leaking then it will require dropping the trans & bellhousing, removing the flywheel, the pan and the rear main cap to fix it. No additive that I am aware of is going to stop it from leaking, thicker oil will slow it down but it will still leak.

[jlthunder]

First I would get under the car with a can of brake clean and clean the oil pan area then run the car and investigate that it is in fact the seal leaking.Check all the oil pan bolts to make sure they are snug. Next inspect around the gasket to make sure it is intact without any gaps. If you are not worried about how it looks, sometimes you can clean the rear of the pan around the seal and smear some high-temp Permatex gasket sealer in that area to help it, if it is the seal leaking then it will require dropping the trans & bellhousing, removing the flywheel, the pan and the rear main cap to fix it. No additive that I am aware of is going to stop it from leaking, thicker oil will slow it down but it will still leak.

Good advise.
My engine was clean since it just came off a rebuild and my leak looked like a main seal. OGTS pointed me to the bearing cap solution and they were right. Start with the simple stuff first as mentioned above before tearing into a rear main seal.

[OpelNewb]

Good grief this problem is too common. Mine leaks as well. I will be tearing into this soon. My engine has a fresh rebuild and the builder was advised about the bearing cap deal but it may have still been overlooked. My leak is pretty bad though. Which is very aggrevating. Drip drip drip when hot. Running right down the back of the oil pan.

[opeldean]

https://www.opelgt.com/forums/6a-engi...ebuild-25.html


look at post 467 in the apprenticing thread. should help you on the main seal install. Its not that bad.mine leaked after the rebuild,so I had to replace it. I ruined 2 seals until I learned the easy way in this photo

[BQS4]

https://www.opelgt.com/forums/6a-engi...ebuild-25.html


look at post 467 in the apprenticing thread. should help you on the main seal install. Its not that bad.mine leaked after the rebuild,so I had to replace it. I ruined 2 seals until I learned the easy way in this photo

Dean;
Not to steal your thunder, but, you also need to explain that the "blue tool" you show in your install pics is the actual Opel tool, which is mine. I'm willing to send it out to those who might need it.

[opeldean]

My engine has a fresh rebuild and the builder was advised about the bearing cap deal but it may have still been overlooked. My leak is pretty bad though. Which is very aggrevating. Drip drip drip when hot. Running right down the back of the oil pan.

Mine leaked after the rebuild too..notice in my photo...I used black sealer on the outside seal. There are 2 spots you can leak that i am aware of....1- the metal to metal interface that jeff speaks of and 2- the outside surface of the seal itself...the seal is not hammered in...its a gentle tap..if you have to hammered it..it gets bent..the key is the plastic sleeve and lots of grease.

PS; THANK YOU Gene for lending me your blue OPEL tool. Its a perfect fit.

[P.J. Romano]

I have made rear seal installer of the scrap metal. It works great.

[Dan-MI]

Why the overhead film? The pics show you cutting it down and leaving it. That does no harm? Does it improve the seal?

[BQS4]

Why the overhead film? The pics show you cutting it down and leaving it. That does no harm? Does it improve the seal?

First, the "blue tool" you see him using is supposed to have a second piece to it. The second piece does what the film does, in that, it helps the actual seal go over the crankshaft surface while tapping the main body of the seal in place with the rest of the tool. I do not have the original second piece, but, Dean is smart enough to have figured a way around it. That is why, if you read the whole thread of Dean installing the seal, he destroyed two seals before getting the third one in. Now, the film, once you get the entire seal properly seated, gets removed. He didn't mention this as it should be obvious. Anyway, he trimmed the film down so it would fit inside the blue tool and allow him to tap the body of the seal into it's proper place.

[kwilford]

First, the "blue tool" you see him using is supposed to have a second piece to it. The second piece does what the film does, in that, it helps the actual seal go over the crankshaft surface while tapping the main body of the seal in place with the rest of the tool. I do not have the original second piece, but, Dean is smart enough to have figured a way around it. That is why, if you read the whole thread of Dean installing the seal, he destroyed two seals before getting the third one in. Now, the film, once you get the entire seal properly seated, gets removed. He didn't mention this as it should be obvious. Anyway, he trimmed the film down so it would fit inside the blue tool and allow him to tap the body of the seal into it's proper place.

I have the same "blue tool" seal installer, which is a special Kent-Moore tool ("Seal Installer" #J-22928-2) specifically designed to install the CIH rear seal. And mine also came minus the second part ("Oil Seal Seal Protector", #J-22928), which, by the photos shown in the 1971 FSM Figures 60-61 and 60-62 on page 60-45) , is a cone shaped piece that the seal is slid over first before it is driven into place over the crank journal. The cone ensures that the seal lip doesn't fold back as the seal is installed, as the lip MUST face inwards to form an effective seal. Dean has devised an ingenious method using the plastic film to form a cone. But care must be taken to ensure that the seal lip isn't folded back. I installed a new rear engine seal in my old '88 Prelude a few years ago when I installed a new clutch, and that seal was even larger than the Opel CIH seal, so it was quite tricky to install without folding the lip back. The film would have done the trick. Good tip Dean!

[zippy7575]

There's something to be said for making sure your rebuilder is experienced with Opel engines. I did a rebuild about 30 years ago via a local mechanic and the rear main seal leaked like a sieve thereafter. I put up with it for about ten years then finally bought a rebuilt 2.0L short-block from C&R Small Cars, which has worked perfectly for about 20 years now. Not sure if OGTS sells short blocks, but if so, that's what I'd do if I had to do a rebuild again.