Hi guys,

My name is Eric and I am new the forum. I have a 99 Olds Bravada with 57k. I bought from a little old lady who only drove to church and back 2 years ago with 36k. The only "mods" that I have are an ebay electric fan kit.

I run Mobile One in all myvehicles and used M1 on my first oil change with the truck. I have no idea what was used in the truck before me but I would assume it was dino oil.

My problem:

I drove the truck for the first time in about 3 weeks and noticed a huge oil spot underneath.

See below. I put my shoe next to it to give everyone an idea of what I was dealing with. That's a size 12 if girls are asking but for you guys its an 11.




So yeah....I was pretty surprised. I changed the oil 2k miles ago and I did notice a very small amount of oil on the oil plug but didn't think anything of it.

I checked the oil level right away and I was a qt low.I added oil and then drove to work.

When I got home Ifollowed some advicefrom the forum and tightened all theoil pan bolts. I maybe got a 1/4 on one of them but the rest were tight. All the oil was on the Front/Bottom/Back of the oil pan. At first its seemed to all be coming from the front. I took off the oil filter shield and cleaned everything up real good starting from the back and working my way to the front.

I spent about 25 minuetson the front of the engine with a snake light and a camera taking a few pics of things that I thought look out of place. But nothing really stuck out to me as being very abnormal. There was no on the block above the oil pan. Thereappeared to be a very small amount of oilseeping from the front of the enginebetween thepan and the block but nothing that would create the spot I found.

Iwent back to the rear of the engine where I had previous cleaned and noticed that oil was starting to seep out of the cracks where thetrans case meets the engine....

So all signs point to a bad rear main seal.

I drove the truck into town on a 40 mile round trip and checked the leak when I got home and sure enough there was plenty of oil on the back of the pan and I could tell that ithad built up enough to start dripping. I put a clean work towel under the drip to see how much I get in the morning.

Does anyone have other ideas of things I can try before I bring it into the stealership and have it looked at? From what I have found onhere it seems pretty obvious. Also, is there a "How To" on replacing the rear main seal? I know it involves a lot of work but it maybe something I feel comfortable doing if I had an opportunity to see what's involved.

BTW

How come you guys don't have any stick'd threads?

Thanks.

 

At the top of the sections there is a sticky named "Helpful Threads - Submit them Here!!" We are attempting to gather threads that members have found useful but it takes member participation. If you come across something that you have found useful/helpful, feel free to post the link there. My understanding is that once they are gathered they will be combined into one thread for the entire site.

I'm assuming since you tightened your oil pan bolts that you've done some searching. This thread also suggests a leaking oil pressure sending unit.

I've also read that switching from conventional to synthetic can cause leaks. Something to do with the seals and the consistency of synthetic after an engine is used to conventional. Might be worth looking into...

EDIT: This thread covers it lightly but there didn't seem to be much followup.

ANOTHER EDIT: This thread covers it a little more in-depth but seemed to end in an argument.

All of this was found using Search function for "Rear Main Seal" and "Conventional synthetic".

 

Pull out the rubber plugs on the bottom of the transmission bell housing. If your rear main is leaking, then the back of the flexplate will probably be wet with oil.

Other possibilities are a leaking oil pressure sensor up at the top of the block at the back of the motor.

 

Last night I pulled one of the rubber plug and looked inside and there was oil on the flexplate. So I made an apt at my local GM dealer today.

They just called back and said that the leak in the rear is from the rear transmission seal. They want $153 parts and labor to fix that.

They also said that my water pump needs to be replaced. They want $480 parts and labor to fix that. $242 for the pump and $215 for labor. I did a quick search and found water pumps for $65-$90 so that is definitely something I am going to do myself.

They also mentioned that passenger side wheel bearing needed to be replaced. Which is really strange because I just replaced that side less then 8,000 miles ago. I know those can be hard to diagnose so I'll take a look at the drivers side.

So I have a little more research to do...

 

Ok this is weird. I am having a problem troubleshooting the "rear transmission seal" that the dealer told me to needed to be replaced. From what I have found the rear trans seal is at the end of the extention housing by the driveshaft. That is no where close to where my oil leak is coming from.

Is there somewhere else I should be looking? Or is there a more common name for "rear transmission seal"?

 

If you are leaking motor oil, then the rear seal that they were referring to is most likely the rear main seal on the engine. Nothing to do with the transmission...

 

Man... I got a 97 with a similar leak at the rear but its annoying size about a half dollar. I will be tightening the pan nuts this weekend first. Could someone point out where the sending unit is..Do i need a special tool for removal?I'd like to take some pics to add the the forum. As far as your waterpump its defiantely a do it yourselfer.. This forum helps me out allot..