Moving on to the business of repair (300SDL burning coolant) - PeachParts Mercedes-Benz Forum

thelazzarusman · #1 03-08-2006, 04:46 PM

Thanks to all who responded to my "I've been had" post. The vehicle's A/C has been repaired succesfully and will go into the dealership tomorrow for the trapox recall, when I can hopefully get all my necessary engine repairs done at little or no cost under the recall

I do have a question about the nature of my coolant burning, if for nothing but a better understanding of the process. The car burns coolant, that's established; however, there is no mixing of engine oil in the coolant reservoir. I suspect there may be coolant in the engine oil, but not vice-versa. Also, although she chugs white smoke sometimes at idle, one she is above the low RPMs, she is smooth and powerful, with no smoke. Most importantly, while I was driving her (which was not long, thanks to my suspicions and your advice!), she NEVER got over 100 C.

Would these symptoms indicate a simple headgasket failure, or an entire block failure? If it's a block failure, why no overheating and the smooth operation above the lower RPMs? This is all quite fascinating to me, which mitigates my anger about being duped in the first place.

Any and all replies appreciated!

DL

dieseldiehard · #2 03-08-2006, 05:03 PM

Quote:

Originally Posted by thelazzarusman

Thanks to all who responded to my "I've been had" post. The vehicle's A/C has been repaired succesfully and will go into the dealership tomorrow for the trapox recall, when I can hopefully get all my necessary engine repairs done at little or no cost under the recall

I do have a question about the nature of my coolant burning, if for nothing but a better understanding of the process. The car burns coolant, that's established; however, there is no mixing of engine oil in the coolant reservoir. I suspect there may be coolant in the engine oil, but not vice-versa. Also, although she chugs white smoke sometimes at idle, one she is above the low RPMs, she is smooth and powerful, with no smoke. Most importantly, while I was driving her (which was not long, thanks to my suspicions and your advice!), she NEVER got over 100 C.

Would these symptoms indicate a simple headgasket failure, or an entire block failure? If it's a block failure, why no overheating and the smooth operation above the lower RPMs? This is all quite fascinating to me, which mitigates my anger about being duped in the first place.

Any and all replies appreciated!

DL

It could be a headgasket, that would be the best thing possible. If not its the head.
read about the cracked head syndrome. The block is not involved unless its a new, never seen b4 problem. Coolant under pressure gets from a cooling passageway into the cylinder
A pressure check with the head off the engine is probably necessary but at that time one can likely see the head gasket and the head and decide which is the culprit

dieseldiehard · #3 03-08-2006, 05:04 PM

Oh, and don't let the dealer remove the head for troubleshooting this problem or you will be in another world of: "I've been had"

Hatterasguy · #4 03-08-2006, 05:09 PM

I wouldn't have the dealer do anything they are going to charge you for. If it is the head you can get a brand new 22 with all the trimmings for about $3k.

Diesel Giant · #5 03-08-2006, 05:11 PM

Head gaskets can blow several ways. Letting oil in the coolant, letting coolant in the oil, blowing exhaust back into the cooling system and letting coolant into the combustions chamber.

To be sure its coolant burning, it will be a thick sweet smell and very white.

hughet · #6 03-08-2006, 06:07 PM

I am going through the same thing and in my case there were cracks in #5 and #6 and there had been moisture in all of the cylinders. The car was overheated for the first time 18 years ago and my guess is that it has not run well since(see my post from last week about my 300 SDL autopsy). I think that the cracking head was a dormant condition that went way back but just happened. The oil was clean but the radiator hose was hard as a rock upon starting. It didn't miss at higher RPMs because the cooling system was pressurized to the point that the cracked cylinders couldnt leak enough to screw up combustion. The header tank was black from soot.

I opted for a new "22" head from Metric because the car is worth fixing. In my case I needed 2 exhaust valves, 6 intake valves and all new prechambers in addition to the head for a total of just over $2,500. Add in 6 new glow plugs, a head gasket set, new tappets and a new style (non exploding) vacuum pump and that gets you up to the $3,000 that Hatterasguy is talking about. The springs were all OK and the injectors pop tested out fine.

What you should do is remove the head and look for cracks between the prechamber and exhaust valve. The cracks on mine were almost invisible but they were there. any pitting in the valves and in the ridge area indicates fluid leaks into the combustion chamber. With the head off, you can evaluate the cylinders and camshaft for wear. In my case the cylinders still had the factory crosshatch on the thrust side, the cam was beautiful and the chain had no stretch which goes along with what most mechanics say about the durability of the bottom end of Mercedes diesel engines.

thelazzarusman · #7 03-08-2006, 11:02 PM

and found the hose soft and squishy after the car had been sitting unused for several days. Is this a good sign?

DL

Brian Carlton · #8 03-08-2006, 11:07 PM

Quote:

Originally Posted by thelazzarusman

and found the hose soft and squishy after the car had been sitting unused for several days. Is this a good sign?

DL

You mention that the car "burns coolant".

Are you positive that it does not "leak coolant"?

The soft hose test should be done the next morning after the engine was run. After several days, the pressure may have bled off.

A definitive answer can be obtained from an oil analysis. For $20.00, you'll know what you have. Why conjecture?

t walgamuth · #9 03-08-2006, 11:15 PM

i would think it means steam coming out the tail pipe on start up. yes after running a few minutes this will not show. it will still be leakning however. the residual pressure in the system will push some water into the combustion chamber after shutdown until the pressure is gone. then on startup poof steam.

i dont think if there is steam on startup there is any other choice than cracked head or bad head gasket. small chance of cracked block. in any scenario it is head off time.

tom w