Coolant leak & mixing with oil
 

I just purchased my '91 Supra turbo yesterday and am very excited about it. I got it for a good price and it is a bit of a fixer-upper. That being said, It is puking coolant and the oil is chalky when I checked it. I took it to a local shop (because they offer free inspections and I don't have a hoist myself) and they showed me what we think is a leaky timing belt cover gasket. This of course is not coming from the top, plastic section, but rather the bottom section. Of course they said it was a 5 hour fix and I am hoping to do it myself. I am in school however and may not actually have the time.

Is this a common issue? Has anyone here had this problem and/or fixed it themselves? I am trying to find out as much information as I can and I am obviously very new to the forum, but I hope to be an active member.

Thanks.

I'm sorry to say exterior leaks are the least of your worries. Oil and coolant cross contamination is indicative of a blown head gasket. Refer to the FAQ section for threads about BHG or blown head gasket for details on the process of how to repair it. It's not a quick or easy job for a novice... It's not a cheap job if you pay a shop to do the whole thing.




Here's a starting point:
http://www.toyota-supra.info/forums/...-symptoms.html
http://www.toyota-supra.info/forums/...ir-w-pics.html

This is what I thought when I checked the oil. However, The exhaust is not white at all and there is no sweet smell. Also, the car apparently has a metal HG with ARP studs torqued correctly. I know that the MK3 had major HG problems with the factory torque specs.

I may be misunderstanding part of your description of the problem... What do you mean the oil looks "chalky". Chalk, soft white stone, used on black boards a couple decades ago?

Oil leaking near the timing belt is not going to affect your coolant in any way. There are a few places where that oil could be coming from: Cam seals, oil pump seal, front main seal, or if the head gasket job wasn't done by the book the lower rear timing case/block union FIPG wasn't applied.

A head gasket doesn't have to leak anything into the cylinder to allow oil and coolant to leak into one another's circuit. The only other ways for the two to mix as you're describing are a seriously cracked head or a seriously cracked block. Just because there's a MHG and ARP fasteners it doesn't mean the job was done right...

Your new best friend: http://www.cygnusx1.net/Supra/Library/TSRM/MK3/

Thanks for your replies and sorry for not making myself clear. It is actually coolant that is leaking from the seal, not oil. I am not certain of what the gasket is actually called, but they described it to me as the lower timing belt cover gasket that the COOLANT is leaking from. The mechanic worked at Toyota in his earlier days and right after discovering where the coolant leak was he checked the oil and was not surprised to see that coolant had mixed with the oil.

To help verify that it is not the HG (which the mechanic said it was not), my buddy is coming over later today with his compression tester.

Again sorry for the confusion and I will have more information to post later today.

Like cre said the coolant and oil systems are separate. Even if it is your coolant is leaking it should not be mixing with the oil. Inside the head are coolant and oil passages the are separated by the head gasket. Again like cre said there doesn't have to be a leak into the cylinders to have a bhg. Therefore your compression may still read normal.

After further review, it is still likely that the HG failed, but after discovering where exactly the leak is, I think that after the leak is fixed, I will be good to go. I'll explain further...

When the HG goes, as I'm sure you all know, the coolant will mix with the oil (current problem with my car), but the oil will also mix with the coolant causing the overflow cap to pop off and various other signs of oil mixed in with the coolant stream. This is not the case with my car. There are no chunks of oil in the rad or overflow or any other signs of oil.

I also talked to the mechanic more and there was a screw missing from when the previous owner replaced the water pump. As a result, the mechanic said that the seal broke which was the cause of a small oil leak that was declared by the previous owner, and eventually the coolant leak that I have now.

To the part that matters... http://www.zhome.com/~aktar/zcar/engine/blockDec17.jpg ... in the picture you will see that at the bottom left of the front of the block, there are holes for coolant (top hole) and oil (bottom hole). This is the gasket that is leaking on my car. It makes sense (to me at least) that the oil started leaking first, and as the seal broke further, the coolant began to leak out and also into the oil stream.

I hope this helps some of you to understand the issue and why we don't think it is the head gasket (which supposedly has been replaced with a MHG and ARP bolts).

I am going to get the shop to take care of it as they quoted me just over $700 including the timing belt since they will be in there anyway.

Thanks again.

I think 700 is a lot to pay to fix a leak. I prefer to do the work my self though. When you own a supra you either need to have deep pockets or be able to do the work yourself. But the hardest thing you should run into would be removing the crank pulley. It is easy to make room to work up front by removing the rad.

So you don't think coolant in the oil is a problem...... You need to start studying a lot and find another mechanic if he agrees with this. This is ridiculous. Of course the coolant leaks first with a leak between the oil and coolant jackets, it's thinner than the oil. It takes a big hole for the oil to enter the coolant system but by then your bottom end may be trashed.

So, to recap, if there is actually coolant entering the oil circuit you have a problem... PERIOD... no ifs or maybes about it.

Also know that just because you have a mhg and arp studs does not mean the job was done correctly. For a mhg the block and head surfaces must be machined smooth. Not to mention chasing threads and a retorque after several heat cycles are never bad ideas. It is very possible to do a hg and have it go bad shortly after.

Coolant in the oil is obviously a problem. I tried to explain where it is mixing but I guess I didn't make myself clear. $700 also includes the timing belt job. I do my own work usually but I am new to the Supra and I don't have tools for the timing belt anyway.

I'm bringing it in on Tuesday. I'll let you know if it is still mixing after.

I was responding primarily to statement:

It came off to me as saying that it doesn't matter that the HG is probably leaking and that after fixing the external leak you've found you're just going to be done with it and hope that fixes everything. From what the picture I've got in my head of what's going on that's just not going to happen and you're just going to end up paying for the labor of removing some of that stuff twice when you have the shop replace the HG next.

There is no way for coolant to enter the oil system and make the oil look like pudding that isn't internal and isn't bad. It's been a while since I've had one apart but I'm pretty sure that none of the water pump fasteners run all the way into the oil galley. So if the oil in the pan is getting contaminated you've still got a bigger problem than just the missing bolts. Drain the oil and look for water/coolant separating or see if it looks like chocolate pudding. I don't know if you're understanding this, being hopeful or if it's just a little more confusion and miscommunication on all our parts but I'm repeating it the one last time. I'm just trying to make sure you have all the info you need to make a good educated diagnosis. Please don't think I'm trying to be rude.

Went to she shop today and saw my Supra in the air. Stopped in and he has it all taken apart and he was right. Just that gasket. He showed me how it was leaking straight down into the oil pan. He also showed me that the car actually does have a MHG that appears to be working. The car will be done tomorrow and ready to go. I plan to run it a few miles and change the oil and filter again.

I am happy that there is nothing else wrong and I didn't have to go through the headache of replacing the HG or anything else. Once I get it back, I hope to upload some pictures and write a description of the things that I actually know about it :P

Thanks again!

If you could get the part number for the gasket from your mechanic I'd appreciate it. Even looking at the Toyota EPC I can't figure out which gasket could allow a leak between the oil and coolant circuit. I've stripped more than a few of these engines and rebuilt a couple and I'm stumped. This is a 7M and not a 1JZ or 1G, right?

I'll get the part number for you when I go to pick it up. I wish I got a pic of it to post. I thought about that when I got home. Yes I have the 7mgte...I can't find anything helpful to show you on the internet.