87 300SDL gets hot in idle
 

Hello everyone.
I currently own a 87 300SDL.
I am trying to figure out if I need a new water pump.
Most days the car runs 85-90C
But on very hot days(over 95F and its very humid)
Or if I am sitting idle in traffic, the temp will go up to
100C. I usually pull over and let it the car cool
or get on a secondary road and drive abit to be on the safe side.
Any thoughts? I searched other post and it seems my
300SDL runs hot compared to others. Please advise
Thanks

Many possible issues
 

There are many possibilities such as:
1. Cracked head:eek:
2. Clogged cooling system/radiator
3. Bad viscous clutch on the fan
4. Inoperative auxilliary fan

All these topics are covered in depth. Use the search button. There is alot of good insight.

At least you know enough to not overheat your OM603 engine.

Fan clutch working?

Aux fan if the A/C is on?

Aux fan switch on motor? They hardly work anymore, $20 and get the RED one.

Condensor/Rad core full of dirt and/or bugs from the last 20 years?

Coolant low?

Bad thermostat?

Is this condition with or without the air conditioning running?

If without A/C, then I'd say you have a cooling problem.

If with A/C, then it may be your auxiliary fan, fan clutch, or some restriction in the coolant flow. But you can generally expect temps to creep up in traffic with the A/C on full blast. Under such conditions 100C is nothing to worry about.

110-120 C is where you get really, really, deeply concerned.

Ken300D

hot
 

The AC is not on.

Unless you've got a pristine radiator, consider this performance normal. Until the fan clutch engages or the aux fan comes on, there is insufficient airflow through the radiator. So, unless the radiator is nearly brand new, the temp is going to climb.

100C. is nothing to worry about. The '86 will climb to 100C. on any heavy accel..........at just about any ambient temperature. It never reaches 105C. and I'm hardly worried about it.

If it bothers you, remove the radiator and spend two hours cleaning the fins using condenser cleaner and/or compressed air and/or a pressure washer. Older radiators and condensers have accumulated a pile of old debris in the fins that you can't easily see.

as always
 

Thanks Gents,
As always, I am able to find useful information and help on this Forum.
That is why I always come to this forum first.
Cheers
A

I don't think this is temp is normal at idle with a/c off - near zero load, assuming radiator is not blocked - and, if temps drop immediately on getting airflow when car starts moving, then check viscous clutch fan first ...

The clutch fan isn't going to pull much air at idle, especially if it's not fully coupled.........which it won't be until the engine gets well above 100°C.

The problem is the older radiators and condensers that prevent proper airflow due to accumulated debris between the fins. The only solution is to thoroughly clean them outside of the vehicle. It's a long tedius process that nobody wants to do..........including me........so the temps will climb at idle in hot ambients (95-100°F).

My SD creeps to about 90°C after about 30min at idle... new rad sitting in the garage. :)