Massive coolant loss: could it be the head?

How hot does it typically get?

Stays at the half-way point like clockwork during almost every driving situation. Gauge drops like it should if I turn on the heater full blast, doesn't rise at all for A/C even in bad traffic. The only time it goes higher than normal is when I push the car going up a hill (then it steadily rises until I calm down) or when I'm driving around town like an idiot, flying out of every turn full throttle (and in this case, it barely goes up at all).

Mike

Done and done... I feel no moisture out of the exhaust at idle, and when revving/under light load, the car puts out no visible moisture. The only stuff I've been able to get out is a spitter-spatter of black guck (either oil, water/soot mix, or something else) out of the tail pipe during a cold idle. Not much at all.

There is one thing, during hard acceleration when the car is just at operating temp, OR normal acceleration in the morning when the car and the ambient temperature (outside) is cold, there's what looks like an exaggerated cloud of what normally comes out of gas car exhausts on cold mornings (steam?). On the freeway, when I can get this to happen (it's rare), the cloud behind is pretty significant, especially when lit up by the headlights of someone following me. I can never get this problem to happen when I want it to... could this be steam escaping until the block/head warms up enough to seal a leak somewhere along the line, or is this cloud normal with the hot exhaust of turbodiesels?

Mike

Well, in light of no obvious leaks you're suspicious of a headgasket. Probably right too, but - first be sure there are no leaks. Drive it and examine everything about the cooling system and heater etc. soon after shutting off the engine. That's when it is at its hottest and the cooling system's pressure is at its maximum, so that's when you'll see a leak. Also check the seam of the block and head.

Thanks for the tips. I'll pull the noise panels tomorrow and check for any drips and whatnot. Where is the best place to check the heater core (my carpet isn't soaking wet).

Seam of the block and the head: it's almost always looked like this, all the way around (with few exceptions):

(the worst area) Pretty much the entire engine block below the head seam is black, caked in what looks like oil with dirt and ash (fires were around here) all over it. The head is almost always spotless. The car doesn't use much oil though... I'll pressure-wash the engine in the next day or two as well to see if I can find where anything is escaping.

Hopefully it's a gasket and not a cracked/warped head, and hopefully it's something even smaller :)

Thanks! Mike

I do not have much experience with MB diesels but have seen many problems like this with other cars including my 500 SEL. When water loss cannot be diagnosed, I always look at the "weap hole" in the waterpump. A small hole which allows any water that gets past the seals to drain out. What happens is the seal only leaks when the engine is running and is under pressure. The water runs down the hot engine and turns to steam, hince no evidence. If you can see the "weap hole" on the water pump on your engine, look for traces of what looks like calcium deposits around and under the hole. If you can see deposits, you have found the problem.

Paul McKechnie

500 SEL

Well is there ANY puddle? That could be the clue. Coolant leaks in your engine in order of likelihood are:

1. Water Pumpo
2. Hoses, radiator
3. Heater core (you can smell coolant in the cabin)
4. Head gasket leaks external
5. Head gasket leaks internal
6. Cracked cylinder head

Bill Ditmire Ditmire Motorworks,Inc.

425 White Horse Pike Absecon,NJ 08201 609-641-3392

I believe you have the aluminum head, so if you can't find any leaks then you probably have a warped head leaking coolant into the combusion chamber, which burns it out so hot you don't see the moisture in the exhaust fumes. I had a similar problem with a 242 Volvo, I pulled the head off, got a fine tooth flat file, and carefully shaved the high spots off the head with the flat file. (For all you naysayers, this technique will not gouge the surface of the head). Then I put it back together with a new head gasket, tune up and so on and my water usage problem was solved with many, many more miles put on the engine.

--Geoff '84 300D

Mike \"Rotor\" Nowak wrote:

Where is the best place to check the heater core (my carpet isn't soaking wet)?

I'd say park it with the engine hot and watch for any dripping under the car.

Don't discount a pin hole leak in a heater hose, radiator hose or the radiator itself.

Good pictures!

Diesels will smoke when cold but that smoke is usually blue. Diesels emit far less CO2 than gas engines thus no "steam" in cold weather - other than in the arctic! So, if your engine is showing "steam" like a gas car you'd better start thinking about the head gasket.

Thanks for all the replies.

I woke up this morning and found quite a puddle:

Looks like it came from the upper rad hose @ the radiator. Tightened the hose clamp but it didn't take much tightening. After sitting for 8 hours or so, there was still pressure in the system.

Took the car to the dealership for another problem, and when I got out, there was a nice little drip coming from the fender resoirvoir tank, and the upper overflow tank was showing signs of a little pressure leakage around the radiator cap neck. The hose that goes from the upper tank to the fender tank is toast, too.

So what does everyone think? Could it just be the 2 resoirvoir tanks leaking, or might this be a side-effect of a blown head gasket/cracked or warped head?

-Mike

Think I've figured it out... coolant is coming out of the fender tank now en masse. The system is getting overpressurized and the coolant is escaping primarily from that avenue but it's finding new and creative ways to bust out (upper rad hose, for example).

Overpressurization is most likely exhaust gasses getting into the coolant system. Everyone I know says if you're replacing the head gasket, replace the head. It's gonna go sooner or later, and it probably already has.

Looks like I'm fu**ed.

Thanks for all the help!

Mike