Head or gasket. - PeachParts Mercedes-Benz Forum

babyjames · #1 11-01-2009, 12:30 PM

Got the '87 to a point where I feel it is actually safe to drive! Three dogbones on each side rear, and the control arm bushing (inner) on the d/s. Still have to replace that control arm bush on the pass, but that can wait for a bit. No major wiggles until you get him up to around 75. Are there Sportline camber links to be used w/shorter springs??

Anyway, any tricks that will help me - short of pulling the head - determine whether the 14 head is cracked, or is it just the head gasket? Oil in overflow tank, and pressure in cooling system increases markedly after prolonged operation. He does o.k. around town, but after a couple hours on the freeway it blows coolant past something on the water pump. There'll be a little (small dinner-plate sized) puddle in the driveway....

I don't want to mess with tearing the thing apart if the head is the culprit, at least not until I have a different head to slap on there.

Right now the thing runs really well, occasional loss of coolant aside.

Bone cold, the radiator hoses are nice and soft, if that is any help.

Cheers!

Jay.

Crazy_Nate · #2 11-01-2009, 12:43 PM

It is my understanding that the coolant system should pressurize (normally from increasing in temperature as the car warms up), however, if the system is airtight, a system that quickly pressurizes may indicate head problems. It sounds like you have a leak, so the radiator hose tests probably won't help you.

Coolant in the oil or oil in the coolant should be more robust indications of problems, however, I don't know if there's any way of definitely naming whether it is just the gasket or a cracked head, short of having the head pressure tested at a machine shop (which shouldn't be too expensive and done anyways as a precaution).

Best of luck...plan for the worst and hope for the best!

sasquatchgeoff · #3 11-01-2009, 01:44 PM

Oil in coolant for me was the time to open the engine up to investigate. Found out the head gasket was not compromised. Head bolts were unusually loose around #4 intake and in the general area towards the rear of the head. Rebuilding the head and replacing the head gasket fixed everything.

sixto · #4 11-01-2009, 02:47 PM

Good bets around here:

1) Oil in coolant = compromised head gasket

2) 603 that pukes coolant = cracked head

Do nothing more than replace the head gasket and hope the cooling issue goes away. In a pinch you can even reuse gaskets. The only things that come to mind that I wouldn't reuse are the o-ring for the fuel thermostat and the gasket for the upper radiator hose fitting at the head. If the upper hose fitting doesn't have to come off the head, that's one fewer gasket to worry about.

A basic digital camera will capture head cracks that have made it to the combustion chamber so you can eyeball those. If you don't see any cracks, put the head back and you're in no worse shape that you were to begin with other than being out the cost of a head gasket and some other gaskets and a couple days' work.

Have you checked the reservoir pressure cap? Maybe it isn't venting as it should. That's what I thought when my SDL head had cracks

Sixto
87 300D

sasquatchgeoff · #5 11-01-2009, 03:11 PM

I guess I should clarify my post a little - the head gasket was not broken through in any place that I could see. The mingling of oil into coolant was apparently happening above/below gasket due to a. corrosion or b. loose head bolts. Here is the area I suspect was causing the mingling, however the front part of the head looked equally suspect. The #1 cylinder area has been cited by the factory as a place for the original, old-style gasket to fail. Corrosion had eaten iinto the head in several places requiring welding. It was very difficult for my non-trained eye to determine the root cause of the oil in coolant problem. Pressure and magna-flux testing showed no detectable cracks.

babyjames · #6 11-01-2009, 10:56 PM

Awright, I'm feeling better. Now if I can just get the FSM DVD thang to load properly!! Maybe take an extra day or two off around turkey day.

Thanks, y'all.

Jay.