Very Slow Coolant Leak: What Are the Risks?
 

I am in the process of monitoring a very slow coolant leak on a 1992 300D (referenced in another post). Over the course of 1200 miles, it has dropped about 1/4 inch with the level having begun at the expansion tank seam. I have observed no evidence of external leaks and no evidence of coolant in either the engine oil or the transmission fluid.

I certainly intend on fixing this, but am also taking something of a leisurely, nonchalant approach.

My question: What damage am I risking by simply keeping an eye on it? If it's an external leak, there doesn't seems to be much risk, other than the possibility of a complete rupture at the point of the leak leading to massive coolant loss. I guess my concern is more with internal leaks, where coolant is bleeding into something else. But, like I say, oil and ATF are clean.

Thanks.

i would try bar's leaks on it.... it won't do any harm regardless of what anyone else says

Thanks for the tip. In the only post I could find

http://www.peachparts.com/shopforum/tech-help/88236-bars-leaks.html

folks had some good things to say. While I'm certainly not part of the absolutely-no-sealants crowd, I'd want to gather some other opinions before using it.

Of the different Bar's products, I wonder which one would be best for my application..

http://www.barsproducts.com/barsleaks_products.htm

Mainly, though, I'm wondering what the risks are with an internal leak.

Ditto. I know for a fact that a very small amount of coolant is making its way into my oil, not because I can see it in the oil (although I do see the coolant level dropping slowly) but because an oil analysis from Blackstone showed "trace amounts" of antifreeze (0.26% after 5,000 miles). They said that this amount was not high enough to be a problem, but they added that the longer the antifreeze is in the oil the more chance it has to damage the bearings.

Like Shertex, I'd be curious to hear what sort of risk one runs by allowing a very minor internal coolant leak to persist.

I've been 8,000 miles since my last oil change (with Mobil 1 Turbo Diesel Truck) with planned 10,000 mile intervals, so I've been thinking about getting an oil analysis....that would be an interesting piece of information.

I'm somewhat less concerned about coolant in the tranny. If it's not visibly milky pink, it's got to be a small amount. And, with 225,000 miles on the original tranny, I'm sure I'll have to replace it before too long.

What was done at mile zero? Did you renew the coolant or replace radiator hoses?

Nothing. Before that, level was about 1/2" too high. So I was content to let it drop, thinking it might be a problem with the overflow tank or hose. Then, when level got to seam, I wanted to see if it went down farther. It has, but rate has slowed.

Do you ever get just a slight smell of antifreeze in the car when the heater is on. I did on my 86 300E last year and I put in a very small bottle of Prestone coolant stop leak. Coolant level stays up now, although I occasionally still smell antifreeze, but that could be remaining from original leakage. But it runs at the same temperature and I have not added any coolant since last winter.

At the rate that you are loosing coolant. I'd venture that you still may have an external leak, but it's drying up as fast as it's leaking. One way to find leaks is to pressurized the cooling system with compressed air, and look around for drips. Do this with the engine off, and you can really poke your head into the tight places, that you might not want to with the car running.

Also, a slight external leak isn't going to hurt anything as long as you keep your eye on the level, and keep it topped up. It is likely to get worse though.

No, haven't noticed anything.

Yes, definitely a possibility. Another thought: if it is an INTERNAL leak (meaning either engine or tranny, right?), then eventually, even if it's a slow leak, it should be visually observable in the oil or the ATF, don't you think? Altogether, the level has been dropping for well over 2,000 miles and the other fluids still look perfect.

You may not be able to notice coolant getting added to your oil in such small amounts, and I've never been able to get a consistent enough reading on ATF that I would be able to tell that small amounts of coolant were being added. I'd pressurized the cooling system and see if you can track down any leaks, then think about an oil analysis to see if it's going into your oil.

I had a nightmare tracing a coolant leak. I looked everywhere and was thinking of doing a head job. It was the water pump that was leaking under pressure nad heat, but ever so slightly that is was not possible to see it for about 2 month. But it was getting loose a bit more as time pass by and one day I was under the beast, engine iddling and really hot and I received a drop of coolant on the face, this is when I saw it was the pump.
Really tricky to find it was.
You might have that too?
I'll look at this before putting any goo in the radiator.
Olivier

i had a leak just like this, there was a very small crack on the bottom of the overflow tank. the leak dripped down in a place where you couldn't see it and dried before the coolant hit the ground, so there was never a drop or puddle under the car. it continued for about 3 months or so until finally the leak got large enough that i could see some wetness somewhere and that led me to remove the reservoir and finally find the leak.

Would the coolant continue to drop well below the seam level in the expansion tank? How low would/could it go? I've been suspecting the overflow system since the rate at which it drops has slowed....but it hasn't completely stopped.