Hello,

Unless my engine is wrong - and Im guessing not, there is no expansion tank like there is on a 300 turbo.

My question is, is the cap used on the tank on the 300 turbo cars the same as on the 240D cars in size?

More practically speaking, assuming that boil-over isnt an issue, there are generally 1.2 and 1.4 bar caps, the 1,4 being the newer part.

What is better? Ive alwys figured the lower pressure item, since the less pressure on system components (and less severe pressure cycles) the better the longevity, right???

Thanks!

JMH

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

240 does not have an expansion tank. Just the radiator. As far as which is "better", I'd go with the higher pressure cap -- it'll let you get more useful cooling out of the radiator without puking coolant when the temperatures climb towards the top end.

__________________
1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER

I would try to stick with what the car is designed for. Going higher may cause things to spring leaks that otherwise would not. If its not cooling correctly I would fix the problem.

Going lower may result in it boiling off coolant when it should be cooling.

Tom W

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

1.4bar is the replacement part.

And that is kind of my point... the car has a cap, 123 part number with an MB star on it, which is labeled "100".

the standard older part for w123 cars was a 1.2 (120 depending on what nomenclature you use) bar cap.

there is a newer w124 cap that is the standard part now, and is a 1.4 bar cap. The 1.2 is obsolete, and is only sold until gone - any new stock is 1.4.

The point about springing leaks is a good one... but it is assuming that the cooling system needs to get to that high a pressure.

Seems responses are mixed. MB claims a 1.4 is good for the car... but maybe the 1.2 is the best intermediate...

Thanks,

JMH

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)