[E36VT]

Basic question - Is there any way to stop a slow gasket leak without taking the head off?

Full explanation of the situation below

1995 E36 M3, S50B30 engine, 129k miles - I've got a slow coolant leak out of the cool-side of the head gasket, exhaust side of the head. It looses about 0.5 liters of coolant every few weeks with regular driving. It's been doing it since I got the car back in 2014.

It has never over-heated, and it has never been a function issue, it's just a little annoying. I brought the car to my mechanic at the beginning of last year to have him remedy the issue. When I dropped the car off with him I noted that there appeared to be a small dribble of coolant coming from the head gasket. This was very concerning to me and I was in the mindset that the car needed a new head gasket. He did a full pressure test on the cooling system, and ended up replacing a few old hoses and clamps, but insisted the little dribble out of the head gasket was nothing to worry about. The oil has never had any coolant in it, and he said he's never seen a head gasket fail on the cool-side with a S50 motor.

I want to believe my mechanic that it's nothing to worry about, but I wanted to see if anyone else has had a similar issue?

Most important, I am going to be selling the car this spring and don't want this issue to effect resale. Is there any way to stop a slow gasket leak without taking the head off?

[stairmast0r]

Originally Posted by E36VT

Most important, I am going to be selling the car this spring and don't want this issue to effect resale. Is there any way to stop a slow gasket leak without taking the head off?

I hope you're not trying to hide the issue and not tell the buyer(s) about it...

[deboM3]

Originally Posted by E36VT

he's never seen a head gasket fail on the cool-side with a S50 motor.

For what its worth, I don't think this is true. Back when my car had 170K on it I had the exact same symptom (head gasket leaking a couple of dribbles externally onto my exhaust, no oil in coolant, no coolant in oil, no coolant in combustion chamber) and I talked to a mechanic who said its a common leak point on the S/M50 & S/M52.

I fixed it myself, and I noticed at about 270K that the dribble is back. I have ignored it and the car has been running great ever since. Im at 302K right now.

But to answer your question, the proper way to fix is to remove the head and replace the gasket. Any coolant additive is IMO a band aid solution and can cause issues later down the line with blocked passages and what not.

[E36VT]

Originally Posted by deboM3

For what its worth, I don't think this is true. Back when my car had 170K on it I had the exact same symptom (head gasket leaking a couple of dribbles externally onto my exhaust, no oil in coolant, no coolant in oil, no coolant in combustion chamber) and I talked to a mechanic who said its a common leak point on the S/M50 & S/M52.

I fixed it myself, and I noticed at about 270K that the dribble is back. I have ignored it and the car has been running great ever since. Im at 302K right now.

But to answer your question, the proper way to fix is to remove the head and replace the gasket. Any coolant additive is IMO a band aid solution and can cause issues later down the line with blocked passages and what not.

When your car was at 170k what did you do to fix it yourself?

Originally Posted by stairmast0r

I hope you're not trying to hide the issue and not tell the buyer(s) about it...

Seriously, was this reply necessary? I'm seeking advice for a mechanical solution, not ethical guidance. Also I'm not a used car salesman by trade... Please stay on topic.

[stairmast0r]

Originally Posted by E36VT

Seriously, was this reply necessary? I'm seeking advice for a mechanical solution, not ethical guidance. Also I'm not a used car salesman by trade... Please stay on topic.

Alright, fair enough

[deboM3]

Originally Posted by E36VT

When your car was at 170k what did you do to fix it yourself?

Removed the head, rebuilt the head with new valves & guides. Machined the gasket surface. Rebuilt vanos. There was a long list in my "top half refresh" Parts alone were about 2K i think, but I didn't cut any corners knowing that I would keep the car forever.

[E36VT]

Originally Posted by deboM3

Removed the head, rebuilt the head with new valves & guides. Machined the gasket surface. Rebuilt vanos. There was a long list in my "top half refresh" Parts alone were about 2K i think, but I didn't cut any corners knowing that I would keep the car forever.

I might have to revisit replacing the head gasket next month when it comes out of storage. I do hate to spend $1500-2000 on something that will not have a proportional benefit on resale...

If there is not a magic bullet I think I'll just have to try selling as-is, and if the coolant dribble scares off to many buyers, then do the work.

Was my mechanic at least correct in saying it's not something to be worried about?

[deboM3]

Originally Posted by E36VT

I might have to revisit replacing the head gasket next month when it comes out of storage. I do hate to spend $1500-2000 on something that will not have a proportional benefit on resale...

If there is not a magic bullet I think I'll just have to try selling as-is, and if the coolant dribble scares off to many buyers, then do the work.

Was my mechanic at least correct in saying it's not something to be worried about?

Well, the first time it happened at 170K miles. I got all worked up and fixed it as soon as I noticed it.

The next time (270K miles) I kinda just ignored it and its been running strong for over 30K miles. I just keep an eye on things. I do oil analysis to ensure no trace amounts of coolant are there, and my coolant levels don't really drop. I also recently passed California SMOG and I have a true coolant temp gauge, so I keep an eye on that.

My only symptom is a slight drip that gets burned up when it drops onto the exhaust header right by the upstream O2 sensors.

If I started to overheat, or my oil was milky I would fix it ASAP. For me, right now, if it keeps on running then I'm happy.

I don't know if my situation is typical or not. Just tryign to give you my experience with this since I have had this twice in my ownership.

[j0rdan J]

I had a friend with this exact issue on his 1999 M3. S52B32 engine. He drove the car everyday and sold it when the leak became really bad (The buyer was a BMW tech and fixed the issue with a new top end gasket set and rebuilding the head). But I do recall before he sold it, he even made a few trips from San Diego to Arizona with the coolant leak on his head gasket.

I think your mechanic is correct by saying don't worry about it unless the coolant loss increases.

[fiveightandten]

External coolant leak on the exhaust side at cylinder 6? It's somewhat common on these engines.