‘76 240D overheat shutdown
 

Dumb me, let my ‘76 240D idle in the heat for a few minutes while I got out for a bit (auxiliary fan is not working). I noticed the car stopped running, and then I heard spewing and hissing. Within the next few seconds lots of coolant was on the pavement. Oddly enough I was at my mechanic‘s place, but he can’t look at it for a while. QUESTION, does the W115/OM616 have overheat protection via a temp switch that shuts the engine down? Or is it more likely that the engine shut down because it is damaged (damage beyond a belt or the radiator)?

I once drove a 240d for 15 miles with a broken fan belt. There was no coolant circulating during that time and the only thing keeping the engine cool was the air blowing over the radiator. This was during the winter and the ambient temp was around 35 degrees F.

As this is summer I would suspect the diesel in the lines boiled and vapor locked the fuel system. This would be the same as running out of fuel.

Turn the engine over by hand to see if it seized. If it turns then you will just have to deal with priming the lines via the hand pump on the side of the injection pump.

That’s good to hear. The mechanic told me later that it ran a bit when they were putting it inside their fence for the night, but it died. So, that should mean it didn’t seize, but it may need the priming as you describe. I appreciate the reply very much.

No overheat protection shutoffs on that car. It either ran out of fuel or got the air intake blocked but the latter is very unlikely OR it was so hot the pistons expanded a lot OR it was out of oil. Was the oil checked, oil pressure ok?

I was driving a 240D in the rain, hit a bumped ripped open the oil pan it seized due to oil loss. Put a new pan on it, filled with oil and drove it for years.

Good luck with yours!!!

That’s one tough cookie. THANKS. P.S. The oil level was good on the car.

There is actually a special tool for priming the diesel in a Mercedes. I have never used one but from what I understand it is an open tube screwed into an injector or the injector port leaving the injection pump. You turn the engine over and watch the markings on the flywheel while watching for the tube to start dripping diesel.

I think the name Mercedes gives this is 'Start of prime'. Any service manual for the car should have this procedure in it. Of course a diesel mechanic should know this as I have heard all of them need this 'timing' set up wen they run out of fuel.

I know this is sketchy, but look into it. If you did vapor lock the fuel you will need this info.

Good to know. Thank you!

Please explain why the start of prime needs adjusting when you run out of fuel? That is a hard setting that only needs adjusting to compensate timing chain stretch.

Please pause for a moment, and recall that the subject of the above quotes is actually "Start of injection". It has nothing to do with bringing fuel up from the tank on the lift side of the pump.

Yup, that is the correct term. It's been a long time since I had to do this so I was doing good to even get close.

A friend of mine's John Deere ran out of fuel. It took the dealer several hours to get the air out and get the thing running.

The only time to adjust the start of injection is when timing chain work is done or the pump itself has been taken out.

[QUOTE=Idle;

As this is summer I would suspect the diesel in the lines boiled and vapor locked the fuel system. This would be the same as running out of fuel.

.[/QUOTE]
Just for the record. Liquid diesel #2 boils at over 500F. Furthermore, that is at STP. Increase the pressure, and the boiling point goes up.
The fuel stays liquid, even at very high temperatures, until atomization at the injector nozzle. Atomization is aided by a drop in pressure when it goes into the cylinder and an increase in volume of the container, injector to cylinder. Added temperature does aid atomization within the prechamber, but that is different than boiling. Think of water, a cold mist is by no means boiling.

This thread and the OP are suspect.