Coolant Leaks / Power Loss 1987 300D
 

Hello all,

I'm writing about two problems with my car that seem to be linked, as far as when they occur. I would really appreciate any help in understanding what is happening.

Issue #1: Leaking Coolant
My 300D leaks coolant intermittently. It was fine the first 6 months I owned the car, but recently started dropping coolant, and I've put almost a gallon in to replace the lost coolant. Sometimes after driving ~40 miles my low coolant light would come back on. However, for about a tank of gas it leaked none--until today.

I've looked all over the engine and found three sources of the leak. These are the upper / lower radiator hose (I tightened the clips on those two hoses), and where the hose to the heat exchanger leaves the engine block (approximately underneath where the air intake for the second cylinder from the firewall meets the cylinder head). I don't know how to tighten this one, as it is a metal-to-metal junction. Can anyone tell me more about this junction and what to do about a leak there?

Also, this has only occurred when it is cold out (I'm in DC) but I'm reluctant to blame it 100% on the cold as it was not leaking last week when it was colder than it is today. Can cold have an effect on the integrity of the cooling system?

Issue #2 Intermittent Lack of Power
The other issue with my car is a lack of power. The car sometimes can't seem to get past ~2100rpm when I try to accelerate. If I really mash the pedal, it will sometimes feel like it "breaks through" the hesitation and start making power again. Almost as if the turbo is stuck, and then spins up, or fuel is stuck, and then flows easily. I'm not sure if turbos, or diesel fule systems have such behavior.

This has only happened when the coolant is leaking (not sure if there's any connection beyond coincidence).

I will add that my cooling system has no pressure in it this morning now that the engine is completely cold, so I do not suspect the dreaded head crack.


--Thanks, I really appreciate your help!!

--Matt

The coolant fitting at the back of the head has a thick o-ring. There's a circlip holding the coolant line to the head. Along the circumference of the circlip there's a hoop you can hook with a pick to pull off the circlip. Then the line will pull out of the head so you can replace the o-ring. It's the same o-ring as used in the heat exchanger line attached behind the water pump, described as water pump o-ring in FastLane. You can check with Phil to be sure.

It's difficult to see a water pump leak in these engines.

Sounds like it's time for new fuel filters and maybe a dose of Diesel Purge.

Sixto
93 300SD 3.0

Thanks for the reply. I'll look into the coolant fitting to the block.

I actually just had my fuel filters replaced two weeks ago in conjunction with the replacement of my fuel pre-heater, which was leaking. My shop (Mitch Carr's) had thought that should fix the loss of power, and it did, for a time, but now it's back.

My pre-filter currently looks sparkling clean so I'm certain they do not need replacing again.

Remove the fuel filler cap and see if there's a strong rush of air. Seems to be a lot of that going around. Inadequate fuel tank venting I mean.

Sixto
93 300SD 3.0