Aux fan problem... I know and I searched

[demetk]

I seem to remember the switches on the e23 rad to be at the bottom right? I always considered their placement very strange when compared to the e28 - top left and e34 - top right. I can't believe that's optimal for accurate temp readings.

[BRRV]

Thermostats often get weak with age and open sooner, I'd guess your stat is just tired.

Been pretty consistent for the last twenty years, regardless of thermostat: and I only buy Wahle or the factory unit (it's been in the car a year and a half). My temp gauge will sometimes ground, too, and not work at all, until I restart. A good tip, though.

[allans356]

Yep. The switches are on the bottom right of the radiator. Seems like it would be hard for air to get trapped down there unless it was blocked.

[BRRV]

My money is on the radiator. Take it for a little drive, doesn't have to be long, pull in and shut it off. Feel the radiator, if it has cold spots it's bad or plugged.

I've had them do both, both get hot at idle when bad and start edging up on the highway over 65-70 when restricted. Especially with plastic tanked ones it's easier just to replace them most of the time.

After fan clutch, this. Thermostats, in my experience, either fail completely or get weak and not allow a car to warm up totally (like Mike said, earlier).

[demetk]

Yep. The switches are on the bottom right of the radiator. Seems like it would be hard for air to get trapped down there unless it was blocked.

That's true, but I would hazard a guess that the switches are reading cooler than at the top left of the rad. When I installed a volvo electric fan in my e34 I added a fan controller with the temp probe inserted at the top left of the rad. Maybe in your case an upgrade in switch placement should be considered.

[allans356]

An update...

As I have said, I bled/flushed the system twice with green coolant. I pulled the radiator today. When I took the lower radiator hose off orange coolant came out. So clearly, It isn't circulating the way it should. I just dropped off the radiator to be tanked and the guy said he could tell there is some blockage but not that bad. He suggested it is the water pump. In my experience, I have never had a water pump go bad without it either squealing like a pig or leaking. The one currently on the car does not exhibit either of these symptoms. What are the possibilities that the impeller is worn down enough to be ineffective?

[Mike W.]

I have twice in my life seen water pumps that had the impeller spinning on the shaft. The impeller wasn't worn, but the hub in a sense was. So possible, but rare, very rare. Might be worth taking a look though. There's also an early and a late M30 stat, the correct one is in there I'm assuming?

[allans356]

I'm assuming it is the right one. I guess I should check the part number. I did test it on the stove so I know it does open.

[allans356]

Okay...
I got my radiator back and the guy said it was about half clogged. Hopefully that fixes both the overheating and the aux fan. I did stick my fingers into the water pump and the impeller is working fine.

[allans356]

I just wanted to say thank you to everyone who gave me advice on this. It is fixed! Turned out to be the radiator. While I was waiting on the radiator to be cleaned, I put a new thermostat housing and thermostat on and all new hoses and a new coolant level sensor. So far, its working nicely. The temp needle just gets a hair over to the right of center. Guess I will never know if I fixed the aux fan problem. Haha.

Thanks again everyone!

[Mike W.]

Cool, glad you got it sorted out. But you can test the aux fan still. Either take off the fan/fan clutch or stick a piece of cardboard inbetween the A/C condenser and the radiator, start it up and keep an eye on things. Be careful, but you should see it come on first low speed, then high. Be prepared to shut it down/pull the cardboard/turn on the heater so you don't overheat it, but you can definitely test it that way. I know I have.