1975 240D overheating!

The radiator blew, then i paid $600 to fix it. Now it overheats! the mechanic is guessing a gasket? or even a cracked head. i doubt that. the hose from the radiator doesn't get hot to the touch and the aux fan (in front of the radiator) doesn't seem to come on.

is this a fan clutch problem or worse??
please help lads.

teddy

[Larry Delor]

Two things come to mind (the less expensive ones,...of course ), first the water pump (belt is on/not leaking/ radiator feels hot all over), and second the thermostat (stuck?). Does the radiator hose seem to become pressurized, more so than you would expect, after around 10 minutes of running?
Did you make sure that the radiator was "burped", and an often overlooked item...the radiator cap...eyeball it closely...hows the spring? hows the gasket?

(geeez, I asked more questions than you did! sorry)

-Larry

------------------
03/83 300D 184k
07/73 280 160k
-88 other 153k

sounds like the cooling system needs to bled. It took more than once to bleed all of the air in the cooling system in 76 240d.

How long does it take to get hot? If you have any coolant flow at all, should take several minutes to warm up.

was the thermostat replaced? how about the cap?

The other suspect is the water pump, would double check that belt is tight and not slipping.

Be careful if you the remove thermostat housing. Bolts can be frozen and wring off if they haven't been removed before.

If you replace water pump use MB pump which is only about $25.00 vs aftermarket.

replaced the radiator and water on my 240 last year at 150K mi, used a 3 tube core, now it never gets hot even with AC on at idle in 100 degree plus in TX

John Wallace

'76 240d

[gmask]

Originally posted by 240 panzer
Be careful if you the remove thermostat housing. Bolts can be frozen and wring off if they haven't been removed before.
[/B]

Any suggestions for what to do if the threads are stripped inside the thermostat housing?

[Aaron]

Just a hint for you all..

Anytime I have a cooling system opened up, I refill as much of the fresh coolant as I can through the upper radiator hose (hold the hose up high to let any air escape. This trick works on all models, especially V8s. When it starts getting full, the coolant will begin to seep from the radiator neck, so put the hose back on and fill any remaining coolant into the expansion tank or radiator tank. Put the heat on high, and run the car until the T-stat opens.

[Tom Drew]

Aaron, which end of the upper radiator hose do you disconnect to pour the coolant into?

[gmask]

Originally posted by Aaron
Just a hint for you all..

Anytime I have a cooling system opened up, I refill as much of the fresh coolant as I can through the upper radiator hose (hold the hose up high to let any air escape. This trick works on all models, especially V8s. When it starts getting full, the coolant will begin to seep from the radiator neck, so put the hose back on and fill any remaining coolant into the expansion tank or radiator tank. Put the heat on high, and run the car until the T-stat opens.

So because you are holding the hose high it forces any air trapped in the engine out? I'm guessing that you remove the end of hose connected to the thermostat housing otherwise the T-stat would have to be open for the water to go anywhere.

[MikeTangas]

I undo the upper hose at the radiator and pour in there. Never any problem with the T-stat, I guess because on the V-8's at least, the T-stat is at the lower hose. Once the upper hose fills, and the level does no settle any further, or the coolant starts flowing out of the upper radiator neck, then I reattach the upper hose to the radiator. Then top off the expansion tank or upper radiator tank (depending on which car I'm working on).

While doing this, I usually have the front end up on ramp, heater/defroster on at high heat. Once full, I run the car and top off as any trapped air is relieved from the system. If equipped with an expansion tank, fill the tank as full as possible, drive a while and check, top off the tank as the system purges air.

[gmask]

Originally posted by MikeTangas
I undo the upper hose at the radiator and pour in there. Never any problem with the T-stat, I guess because on the V-8's at least, the T-stat is at the lower hose. Once the upper hose fills, and the level does no settle any further, or the coolant starts flowing out of the upper radiator neck, then I reattach the upper hose to the radiator. Then top off the expansion tank or upper radiator tank (depending on which car I'm working on).

While doing this, I usually have the front end up on ramp, heater/defroster on at high heat. Once full, I run the car and top off as any trapped air is relieved from the system. If equipped with an expansion tank, fill the tank as full as possible, drive a while and check, top off the tank as the system purges air.

On the M130.923 the T-Stat is on the Upper Hose so I don't think that this technique applies. What I have been doing is running the engine and adding water as it goes down and air bubbles out.

I may also have to run it for as much a half and hour so that it comes up to temperature if it was a cold start otherwise the T-stat will be closed and I trap air in the head (that's my guess at any rate).

I don't think I had the heater turned on though so maybe I should remember to do that as well. This engine also does not have an expansion tank.

[MikeTangas]

If the T-stat is at the upper hose, then try filling the system backwards through the radiator. Undo the upper hose at the T-stat housing, and fill the radiator, keep filling slowly until coolant comes out the t-stat housing. Should work as there should be a check valve (or the hole where the valve mounts if you popped the valve out [recommended]), which will alow some coolant to bypass the stat.

Gotta have the heater/defrost on high heat.

[Aaron]

Even though the thermostat is in the upper hose section, it will still allow enough coolant to flow past it. Just disconnect (as Mike said) at the radiator and begin filling until it starts going really slowly through the upper hose. Reconnect it at the radiator and top up the expansion tank.

[leathermang]

240 panzer, Where did you get that 3 tube core radiator ?....

Since your here in Texas you might want to come to the Texas MB Shindig in Austin at McKinney Falls State Park... info is on a sticky on the Diesel discussion... welcome to the forum... Greg

[gmask]

Originally posted by leathermang
240 panzer, Where did you get that 3 tube core radiator ?....

I was wondering the same thing?? How much?

[240 Ed]

If you unlucky, the thermostat will stick closed. This can be disaster, as it will cook your engine even if the water pump is working(it can't circulate the coolant to the rad because it is blocked by the closed tstat.) Usually they stick open and you will get a cold running engine.
I always recommend you buy original equipment tstats, they are worth it.

Follow the worthy advice for bleeding the system with a new tstat installed and you will be good.