Went out to visit my son yesterday and found myself in traffic on freeway due to big rig overturn. Road report said an hour wait. Tough luck but my 1989 300SE is ok comfy and Blaupunct radio to console me. Cabin starts to warm up; outside temperature is 63F, its 8:30am in SoCal. I look at the temperature gauge and its reading 120!! What! Road report said right four lanes blocked so I am in the fast lane next to Fast Track lanes. Until I saw 120 F on the gauge I was content to creep along but now I am concerned. Others before me went in Fast Track and I soon followed. Within a short time the gauge was getting back to normal. There was no noise of a water pump going out. I had enough coolant before leaving home. Thermostat needs to be replaced? Coolant temperature sensor?
I also drove the car home with no temperature problems.
Fan clutch is not engaging IMO, At 120 you should hear the engine roar as you accelerate. On my 300SE you can hear the fan clutch roar at 90 degrees displayed. The aux. fan comes on much later than the fan clutch. I would also not rule out a weak radiator cap.
Fan clutch should have kept it down some and yes Aux fan should have kicked at around 90 or so (the one I had did anyway). For a gas saving measure (and that the fan clutch locked up on me) I installed an electric main fan mounted to the radiator wired through a fused relay with the A/C circuit energizing it, later added a fused fan switch on the dash panel
Thanks so much for your input.
I did not hear anything kick in. Being surrounded with traffic in the fast lane I had visions of causing more traffic problems and so I went into the fast track lane and soon after the temperature went down.
The fan clutch was replaced 2003 with the thermostat. I paid to have that done but I want to do this one. Any tips for replacing these?
The problem is not your thermostat, so you can forget about the effort to replace it. If the thermostat was bad, the temperature would not have returned to normal once the vehicle starting moving again.
The fan clutch is certainly important to keep the temperature at a reasonable level when the vehicle isn't moving, however, with a OAT of 63F, it's going to be highly unlikely for the clutch to engage. Remember it needs about 210F to engage and it cannot reach that point typically until the a/c is on and working hard.
My guess is that the radiator is well beyond its useful life. As they age, their capability to transfer BTU's to the air gets reduced significantly.
If you don't want to replace it, you can also try to salvage it somewhat if you remove it from the vehicle and thoroughly clean it with compressed air and some commercial condenser cleaner. The passages are quite narrow and they accumulate with a massive amount of debris over the years. You cannot see any of this debris unless you get your face right up against the fins with a strong light. This isn't possible to do with the radiator in the vehicle.
I gave up on chasing overtemp issues on the SE and just put in the Nissens. It now stays below 100C even in bumper to bumper traffic at 90F ambients, with the a/c on. Remember, these systems are marginal even with brand new parts, so you have to err on the side of caution if you expect "challenging" operating conditions.
Ok. I see the Nissens now at AutohausAZ. Thanks again.
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