Sorry for the new topic, but I need all the help I can get at the mo...

I'm trying to figure out why my engine gets so hot (M103).. I took it to the Mech. and we played with it. We noticed that under acceleration, the *bottom* hose would collapse.... and *slowly* return to shape....

What would cause this?

We've ruled out head gasket, because there are no exhaust gases present in coolant.

Clogged rad? Thermostat? Resevoir tank cap (rubber seal is peeling off and looks dodgy.)?

When I accelerate tho, the temp does drop (normal running 90deg and idle 100deg...)

I'm scared to drive her incase she overheats suddenly

Thanks,

Brian

<desperate>

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Brian Drought
1991 300CE
http://www.users.globalnet.co.uk/~drought/
ICQ: 2180069

Brian,
The t-stat is the most likely cause when running. They are bad about just comming apart. With the engine cold, remove the three bolts and remove the t-stat cover. Remove the O-ring with a pick and the t-stat will lift up easily in your hand. Replace it then, it is inexpensive insurance. If the t-stat cover is plastic, replace it with a metal one. And be VERY careful with the upper radiator connection. Very good chance of breakage. You can see if the neck has been upgraded with a metal sleeve inside of the neck. If not, check carefully for cracks. If present, have a radiator shop replace that the side tank with an updated one. $200.
If your hoses collapse after a cool down, the radiator cap is not venting and needs replacing.
Have fun and stay cool,
turbo herb

The thermostat is not opening fully creating a great amount of suction, which in turn speeds up the flow of coolant by 2-3 times normal. This in turn creates a venturi effect( Bernellis Theory ), and cause things to contract within .

But I also failed science........

Just a guess, but maybe one of the techs showed rubberstamp this with there approval, or toss it into the scrapheap of suggestions.

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Chris Ecklund
98 300 DT

The lower hose is a suction hose, normally, there is a big coil spring inside the lower radiator hose to prevent it from collapsing.

Bad coolent cap will cause overheating problem. It is cheap, listed $6.25.

David

[This message has been edited by be459 (edited 09-11-1999).]

In which case, I'll try the hoses first

At the moment, the only water circ. I've got is thru the heater matrix with heaters on full (and its 80deg outside!!). Also water flows back to the resevoir tank via the return hose on the very top of the rad, so essentially the rad isnt cooling.

Odd problem.

Thanks,
Brian


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Brian Drought
1991 300CE
http://www.users.globalnet.co.uk/~drought/
ICQ: 2180069

Brian,

Here is my suggestion:

(1) replace the lower radiator hose since the inner spring is missing or rusted away.

(2) replace the cap on the overflow container.

(3) Check the overflow container carefully for cracks. Replace it if necessary.

(4) Fill the overflow container up to Max when the car is idling.

(5) Close the container tightly with the new cap and test driver the car for 10 to 20 min. and watch for overheating during driving.

(6) Stop the car and check for leak. The upper radiator hose should be very hot and pressurized by now.

(7) Wait for engine cool down and check the coolent level. Fix any water leak if necessary.

(8) Repeat steps 4, 5, 6, and 7 above if the coolent is low after engine cool down.

If you have airlock problem, that should take care of it.

David