Over Heating
 

Hello Everyone..

I have a 1993 4matic. Whenever the A/C is on and driving, she is a beauty but whenever she stops for about one minute, the temp.gauge goes high...
Any help would be appreciated.... Hari.

Are you sure it doesn't get hot at a stand still with the A/C off? If the electric fan(s) in the front is not working, the A/C will not perform well but the engine shouldn't get too hot so soon.

Check the fuse at rear of the fuse box (rear fuse box cover have to be remove) 15Amps fuse at top of the aux fan low speed relay...is very common that fuse is cause aux fan inop at low speed.

First, do the aux. fans come one when it the needle rises very high with the A/C on? Second, nect time the needle is around 100C sometime, watch the engine fan (fan clutch) and have someone turn the car off. If the fan keeps spinng more than 2-3 turns, your fan clutch is bad. My dad's 300E needs one as the needle will go as high as 110C on a 90F day.

Thanks
David

Over heating-Thanks for the replies
 

Thanks for the replies.. My car doesn't get hot when the A/C is off. I will check the fuse and also the Fan Clutch.... Again thanks

Next time you're stuck in traffic and the needle starts climbing, rev the engine to 2000 rpm and hold it there for a few seconds, if the needle starts dropping your fan clutch is OK and the radiator is working.

If the needle doesn't drop rapidly, either your fan clutch is bad and the fan isn't drawing any air or your radiator may be blocked internally.

To check the radiator, take the car out for a run to get it up to operating temperature, switch the engine off and check the radiator core by putting your hand down the back by the fan. If its hot at the top and cold at the bottom, or vice versa, the core is blocked and you'll need to replace the radiator. Or get it flushed and hope it works.

You may also have a faulty thermostat valve, whch stops the coolant circulating. Plenty of info here on this if you do a search, but you basically have to remove the thermostat and boil it in a saucepan of water to see if it opens or not.

In my opinion, most likely cause of this overheating is air in the system. Have you recently changed coolant or drained the system and topped up? If so, you may well have an air pocket in the cylinder head. You need to undo the bleed bolt in the side of the head and add more water until it comes out of the bleed hole. It's actually easier to remove the temperature sensor as the bleed bolt is kinda fiddly and its easy to strip the threads.

good luck

Definitely check your fan clutch. My car used to exceed 120 degrees C,and the electric fans had a hell of a time cooling the beast down. Changing the fan clutch cured that. I have a DIY web page that outlines the procedure for a V12. Click on the link below my signature.