Coolant res. cap (stupid question)
 

Ok, so my res. cap busted. I need a new one, mine says: "100" on it, along with 123 501 0015... All the ones I find say "120" on them... application is 1983 300td...

What do I do?

GottaDiesel,

Fill your cooling system with EVans waterless coolant and just leave the cap loose. That's what I did.

I also run my '79 300SD beater using antifreeze/ water coolant with the cap loose with no cooling problems. The heater does not get as hot in the winter though even though the temp gauge reads normal. So sometimes in the winter I have to tighten the cap to get enough heat inside the car.

P E H

i have an 83 300tdt it uses a 13# cap.
MADSEN

GottaDiesel,

Check Fastlane by going to the on-line catalog and punching in your car's model and year. They tell you which cap to use and apparently the original cap has been superceded by one rated at a higher pressure for the W124, but they have some original parts in stock or can get them. I do not think it makes a big difference unless the pressure setting is too low, and the coolant is released when the engine temperature gets near the red zone. So, buy either the 1.2 bar setting cap or the 1.4 bar setting cap. Good luck, Jim

Hey, call me crazy but I see no reason to use a higher pressure cap just because they don't feel like sourcing the old "100" or 1 bar cap. Actually I use a standard 7psi cap on my 84 300D. Take your cap to the nearest McParts store and pick out a matching cap in whatever rating you want. 7, 11, 13, etc. psi. I use the 7 psi as I see no reason to overstress a 20yr old cooling system and heater core with a 1.2 or a 1.4 bar cap. I've been running a 7psi cap for 6 months with no problems, overheating, etc. Runs the same temp it always has. RT

Higher pressure gives better boilover protection. I would never use a 7 psi cap, nor a "McParts" cap -- the 7 psi cap will allow the coolant to boil below the red mark on the gauge, and the cheapo caps usually don't fit well.

Peter