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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3567
Experience:  Qualified Mercedes Benz Diagnostic Technician - 20+ years experience - Workshop Foreman for Mercedes
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A question about cooling. One of my 190d's, the nonturbo,

Customer Question

A question about cooling. One of my 190d's, the nonturbo, has always ran hot. Well not so far above 80, but at lights it has a hot effect of dropped idle and oil press. It freaks my girlfriend out worrying about oil press. I know this is common w diesels,
but my other two 190's dont do this. On this one, it has a new water pump and ive drilledmore and more holes in the 85 thermostat such that now i wanna just remove the thermostat. What causes this drop effect when its hot? I flushed the cooling system already
too, using gl-05 coolant and a good pressure tank cap. Should i consider taking my radiator to a shop and having it boiled out? Thanks man
Submitted: 1 year ago.
Category: Mercedes
Customer: replied 1 year ago.
Btw, the concentrated treatment of liquimoly diesel purge on this car is amazing. Night v Day. Power, better economy, quieter, nicer idle. I never thot a chem treatment could do such things
Expert:  Marty replied 1 year ago.
Hi, I'm glad to hear that the LiquiMoly helped the running. If the car runs hot at idle I'd be looking at the cooling fan function. The diesel should use an electric fan clutch along with an auxiliary fan for the a/c condenser. I'd check to see if the electric clutch is engaging at idle when the temperature reaches 100 degrees. It's normal for the temperature to creep up towards 100C at idle. There is a low and high speed fan relay along with a fan resistor for the auxiliary fan. The fan should run at low speed with the a/c on. If the car runs cool when driving down the highway the radiator should be fine. If the car doesn't cool down when you drive or if the temperature creeps up I would clean or replace the radiator. Do not remove the thermostat or the car will run even hotter. You need the disc on the bottom of the thermostat to close off the bypass port when the thermostat opens.

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