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 They tell you which cap to use and apparently the original cap has been superceded by one rated at a higher pressure for the W124, but they have some original parts in stock or can get them.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

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

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

__________________
When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K

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

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!