Running warmer than usual

[nadodude111]

Concerned and confused as to why my car (1991 325i) is running warmer than usual. Hoping someone could point me in the right direction if I list the symptoms and car’s cooling history:

Historically:
- gauge needle always sat between 1/4 and 1/2.
- has needed a new fan clutch as it will warm up to the 1/2 at idle and cool back down when driving.
- replaced the thermostat and water pump about 15k miles ago.

As of today:
- car running at 1/2 mark even while doing 75 down freeway sometimes a hair over or under the middle mark
- needle sits on or very very slowly passes the 1/2 mark at idle
- needle is jumpy when moving up or down the gauge, but does settle so think the reading is accurate.
- needle is between 1/2 and 3/4 after turning car off and putting key in position 2 but not on. Needle quickly moves back to middle when I turn car on.

5 mins after driving 70 miles I checked:
- upper and lower radiator hoses were all warm/hot
- was able to take the expansion tank cap off with no pressure and it was full and didn’t have oil or gunk in it/was clean.
- checked oil in engine and it was clean.

What are some things I should focus on?

Thank you! zz0.3nk9bb5hshozz

[nadodude111]

Well, took it out for a three hour drive and it seems to have fixed itself. Temp gauge needle sits a couple hairs above the 1/4 and only rises to the middle when idling at a stop light (needs new fan clutch). Perhaps the nut on the cluster is loose?

[Panici]

Get yourself a VDO water temp gauge for future use.
They used to make a vision black series gauge that looks perfect in an E30. Might still be able to get one.

It was the first aftermarket gauge I added in, threaded right into the (early) M20B25 thermostat housing on my car with one of the included adapters in the VDO kit.


(WOW this was 10 years ago now!)

[reelizmpro]

If it's jumpy then you know there is a grounding issue. Try tapping the cluster in front of the gauge to get it to settle. Mine sometimes reads high even with the nut torqued down and solder reflowed on the main board. I've been told that the SI board could be the culprit but I haven't gotten around to changing it since the car is not actually overheating.

[bangn]

Factory gauge is shit and whats funny is the temp differences that move it from half to 3/4 are tiny. Invest in a better temp gauge but in hot climates its not unusual for those gauges to read between half to 3/4. Having said that I had a similar issue as you did and I found the issue was silicone from a previous waterpump install had got stuck in the tiny coolant holes in the headgasket.. really easy to do

have you replaced the gauge temp sender yet?

[nadodude111]

It was the temp sensor. Replaced it and needle is back to between 1/4-1/2 and steady. Before that, I tightened the nut on the cluster, replaced the fan clutch and bled the system and the needle kept jumping. Thanks for the help yall!

[reelizmpro]

I forgot to mention the temp sensor which is part of the equation but those hardly ever go bad. I guess every part has a lifespan.

[nadodude111]

I forgot to mention the temp sensor which is part of the equation but those hardly ever go bad. I guess every part has a lifespan.

The temp sensor looked like burnt ass. It was definitely the original 33 yr old part. Your suggestion was great. But I had already changed the SI board batteries and ensured the nut was right.

[nadodude111]

Get yourself a VDO water temp gauge for future use.
They used to make a vision black series gauge that looks perfect in an E30. Might still be able to get one.

It was the first aftermarket gauge I added in, threaded right into the (early) M20B25 thermostat housing on my car with one of the included adapters in the VDO kit.


(WOW this was 10 years ago now!)

That’s a good idea. Using that digital gauge or even a IR gun, What should healthy temps be? I have an 80 Celsius thermostat in the system.

[Panici]

That’s a good idea. Using that digital gauge or even a IR gun, What should healthy temps be? I have an 80 Celsius thermostat in the system.

The analog VDO gauge is the one I was referencing.

It's displaying water/coolant temp in degrees F.
You can actually see the cooling system functioning.

Water temp rises until the rated thermostat temperature (80C / 176F), and then typically falls slightly as the slug of cold coolant from the rad joins the system as the thermostat opens.

If functioning properly you should see the temperature hold quite steady at the thermostat temp. If you cooling fan(s) can't keep up you will see it rise if the car is stationary, and fall again once you are moving and air is flowing across the rad.


In the case of a mechanical fan delete with an electric fan upgrade, you will see the temp hold steady until the rad is thermally saturated. Then it will rise again until the temperature switch kicks on the electric fan. Video below of my car doing that with a SPAL pusher fan and mech fan delete (when I was still M20 equipped.)

https://www.youtube.com/watch?v=mVZE4X-OhKg&list=PLD68RiPVWELXksp6cm4i97XwM6adrVcQo&index =18

[82eye]

i like the idea of that extra analog temp gauge.