Cooling System Riddle 1991 350 SDL - Page 5 - PeachParts Mercedes-Benz Forum

Fulcrum525 · #61 02-04-2011, 05:58 PM

Quote:

Originally Posted by GregMN

http://www.amazon.com/UVIEW-560000-Combustion-Leak-Tester/dp/B000NPDL76/ref=sr_1_fkmr1_2?ie=UTF8&qid=1282707791&sr=8-2-fkmr1

hmm, that's the same that was used on mine and it came back positive right away....odd.

toecutter · #62 02-04-2011, 06:33 PM

Quote:

Originally Posted by GregMN

...
The overflow bottle had about 4" of coolant in it. (it started empty)
The system was pressurized enough to be pushing air and/or coolant into the overflow bottle (very little, very slow gurgling) for about 5 to 10 minutes after I turned off the motor.
The reservoir was still full up to the "max" level.
There were some very slight gurgling sounds that seemed to be coming from the intake side of the head...

you have a cracked/warped head, and/or bad head gasket. period. have the head magnafluxed or pressure tested.

W124 E300D · #63 02-05-2011, 05:17 PM

MB has a bypass tstat, not a regular one, a water circ pump will push 2 bar against a dying tstat, which would tie in with no gas contamination of coolant...

ppls are usually way too quick to blame heads and gaskets, and new heads and gaskets coincidentally will fix many other issues... by simple fact of disassembly and reassembly.

toecutter · #64 02-05-2011, 07:09 PM

but it's not going to magically make bubbles appear in your system. and the t-stat has already been ruled out, according to the op.

i can't remember where the t-stat housing is on this engine, but if it is in the usual place (near top and front of head) there's a relatively simple test. remove the housing and t-stat, leave enough coolant to keep the exposed part of the housing full. disengage the water pump drive belt. start and rev it up a good bit over a minute or three. shut it down and keep a close eye on the coolant in the bottom of the housing. if you see any bubbles at all, even a really fine fizz, you have a compression leak in the cooling syatem. proof positve. i've been down the cracked head/gasket dusty road more than once.

babymog · #65 02-05-2011, 08:34 PM

The thermostat on the 60x engines is on the side of the block, and it is a really bad idea IMO to run a 60x engine without coolant in the head. Really bad.

toecutter · #66 02-07-2011, 08:08 PM

Quote:

Originally Posted by babymog

The thermostat on the 60x engines is on the side of the block, and it is a really bad idea IMO to run a 60x engine without coolant in the head. Really bad.

that being the case yes bad idea, really bad. and totally pointless, if the head has no coolant, there's nothing to make bubbles in. too bad, it's a relatively easy test. like i said, i couldn't remember where the t-stat housing is on this engine, in most of the enigines i deal with the housing is at about the highest point on the engine. top, front and centre.

but quite often if you shut it down, and hear "blub blub blub" in the waterjacket, be patient and look real close at what's going on in the overflow reservoir (even put the hose into a clear jar) you'll see the fine fizz as the level rises.

another simple diagnostic, get it up to running temp and get a feel on both the top rad hose and the bottom hose. there should be about a 20° c difference between the two, bottom being the cooler. if they are both hot to the touch, this would indicate either faulty thermostat or clogged radiator.

GregMN · #67 02-18-2011, 03:13 PM

I just finished replacing the head gasket. That seems to have fixed the problem. I drove 25 miles at 70mph with no coolant loss and no high pressure in the cooling system.

I still do not know why combustion gases were never detected.

Thanks for all the other suggestions, but, "if it walks like a duck, quacks like a duck, looks like a duck, it must be a duck".

cscmc1 · #68 02-18-2011, 03:16 PM

That's great news -- glad to hear it!!!

lgreeley83 · #69 02-17-2014, 07:52 AM

Good read. Still own the car? How's it holding up.

GregMN · #70 02-17-2014, 10:15 AM

The head gasket repair has held up fine. It doesn't get driven much anymore, too many cars. I have driven it to AZ and back 4 or 5 times (3800 miles). It has been sitting out under a couple of feet of snow. I haven't driven it since last Aug. I spent an hour digging my way to it, then getting the snow off the hood on Friday. I put a good battery in it and started it. It was maybe 10 degrees out.
It has rust issues, and I need to replace the upper ball joint (which I have in a car out in the woods). Then I am ready to drive it to AZ again on VO. Everything still works on it, A/C, CC, PW, PL. It has a lock up diff. that really helps in snow. But it is rusty, and the B3 valve in the transmission leaks, so no reverse. I have a spare trans, I just haven't taken the time to fix it. I drove it for 2 years w/o reverse.
I am shopping for a new car for my wife. I will probably have to travel to get what I want. I have a couple I am looking at in AZ. So, may drive it to AZ and leave it there. Maybe sell on CL for fuel money home, or see if a scrap yard with pay anything for it. Or, just give it to a forum member in the area.
I really love that car.

Mxfrank · #71 02-17-2014, 02:53 PM

If the cap is ok, take a close look at the filler neck in the header tank. Look for cracks or irregularities in the sealing surfaces. I would almost go so far as to suggest substituting a new tank.