Author Topic: Engine temperature has creeped higher over time (Read 5050 times)

sopicki · « **on:** April 20, 2018, 08:28:39 PM »

Hi all,

I've had my 1991 318ic with M42 for 9 years and have kept things running pretty smoothly just reading posts on this site. However I have not seen a post of my issue exactly so I thought I'd throw it out to those here with experience.

My normal operating coolant temperature has been creeping up ever so slightly over the last year or so. Right now when running down the road at highway speeds it is about 1 to 2 needle widths above the halfway mark. Although this is still in the normal range I don't really like seeing it there since for the last 8 years it was rock steady on the halfway mark. I've got just under 220,000 miles. Over the winter I replaced all hoses, water pump, thermostat, belts and a slew of other parts with absolutely no change in the temperature. I have no coolant in my oil or oil in my coolant and my compressions were 185, 187, 185 and 186. The gauge is rock steady so I do not suspect a loose ground or other wire.

My gut says change the temp sensor but wanted to check with the experts before I do just in case I'm missing something.

Thanks,

monty23psk · « **Reply #1 on:** April 21, 2018, 08:42:11 AM »

Does it creep up at idle (at a stop light)? How about when you hit the highway, does it start to creep back down? I would first say it is the fan clutch if this happens at idle.

sopicki · « **Reply #2 on:** April 21, 2018, 06:17:41 PM »

Monty,

Thank you for your reply. The temp is rock solid at the one to two needle widths above the center mark whether sitting at a light or running down the highway. It will cool off a little during extended idle.

Thanks again,

Bob

monty23psk · « **Reply #3 on:** April 21, 2018, 08:07:38 PM »

It it cools off after it sitting there, the fan clutch could be kicking in but much later due to being faulty. With the m42, cooling is always an issue. Check at the date of the fan clutch manufacturer date and if it is over 15 years old, I would replace it anyways, call it preventive. It it not that expensive. Also, do you see the temp rise if the AC is on versus off? The AC will add extra stress and heat to the engine. Also, maybe your aux fan is not kicking on. did you change the temp sensor on the radiator? The aux fan two speeds can be tested.

sopicki · « **Reply #4 on:** May 06, 2018, 10:46:26 AM »

Changed the fan clutch and we�re cooling much better! Not quite back on the center line of the temp gauge but running down the highway it�s just a hair above the line.

I bought a clutch from O�Reily�s and is says made in China so we�ll see how long it lasts.

Thanks for the advice!!!

Bob

monty23psk · « **Reply #5 on:** May 06, 2018, 06:40:53 PM »

Thats good news. Another thing, the fan blades matter in the direction they are facing, push vs pull. It should be pushing air towards the engine. My car, when I got it back in the day was incorrect. I noticed this when I removed it when I added the SPAL pusher fan.

sopicki · « **Reply #6 on:** May 10, 2018, 09:57:37 AM »

Well not so fast.......

Driving to work, a 1 hour drive on the hwy, engine temp returned to its previous 2 needle widths location. In addition I discovered a leak on my radiator at the base of the expansion tank. I removed the radiator then removed the tank to discover a crack in the plastic base of the tank so I purchased a new radiator and disassembled the old radiator.

Mind you I use dexcool mixed 50/50 with distilled water and change every 4 years. I�ve done this for 20 years or so with terrific results so I�ve never suspected my radiator would be anything but in the condition it was in when I purchased the car 9 years ago. Attached is what I found when I pulled one of the tanks off. I have no idea what the deposits are. It brushes off easily with a finger and for all I know has been there since I bought the car.

Needless to say I thought I had discovered the cause of my warmer temperature. I installed the new radiator and took her for a drive and.......no change in the temp! STILL 2 needle widths above the center.

So to recap I�ve changed all the hoses, the thermostat, the fan clutch, the water pump and now the radiator with NO change in the operating temp of the engine. Either my engine is running hotter for some reason outside of the cooling system or my gauge/sending unit is at fault.

monty23psk · « **Reply #7 on:** May 10, 2018, 07:16:04 PM »

it is warmer outside but that should change things. I have a coolant pressure tester to help detect leaks. If you were close, you can borrow it. It is from Stant and I have the radiator attachment for the m42. If the sender is the original, it wouldn't hurt to change it. It is not expensive. I know if the grounding nut behind the guage is loose, it can give a bad reading. Thermal guns can also help to tell you the temp of the engine as well.

sopicki · « **Reply #8 on:** May 13, 2018, 11:01:13 AM »

Alex,

Thank you for your reply. I'm quite certain that I'm not leaking coolant but thank you for the offer of your coolant pressure tester....very kind!

The temperature behaves as if it is being regulated at the 2 needle widths position by the thermostat. If I were running out of cooling capacity (thermostat fully open) I would see the temp change going up hill and down hill, or change when stopped at a light vs running down the road, but it is quite solid during all of these different times. Replacing a partially blocked radiator like I had with a new fully open one would have certainly caused a change in behavior and I had loose wires on the fuel and temp gauges when I bought the car 9 years ago (I believe the seller sold it to me cheap because the temp gauge would sail into the red after a couple of minutes because of a loose wire.....something he did not disclose) but the gauges were erratic and not steady as they are now with tightened nuts.

I'd check temps with my laser thermometer but I do not know what temp corresponds to what marking on the gauge itself.

I think the next step will be as you suggested, replace the sending unit.

I'll be back!

mmkale · « **Reply #9 on:** February 07, 2019, 10:05:54 AM »

temp gauges can't be trusted. bad ground makes them act wierd.

sopicki · « **Reply #10 on:** February 15, 2021, 02:23:47 PM »

Just FYI,

Here we are several years later and my temp is still rock solid at 2 needle widths above center. I did change the temp sensor (in addition to all of the other parts I listed) with no change either. At this point I'm comfortable with the temp where it is and assume that it's just the new normal.

One other possibility is that I had a water pump shed its crappy plastic impeller a while back (a previous owner install), before my original post and I never did recover all of the plastic pieces. I'd bet that someday, when I pull the engine apart for a rebuild, I'm going to find a piece of that water pump partially blocking a water passage somewhere. As I said years ago, the temp is still in the normal range its just a little warmer than it used to be.

Cheers to all!

monty23psk · « **Reply #11 on:** February 15, 2021, 07:29:45 PM »

cool update even if it has been a few years. Good to see it still kicking.

Author Topic: Engine temperature has creeped higher over time (Read 5050 times)

sopicki

Engine temperature has creeped higher over time

monty23psk

Re: Engine temperature has creeped higher over time

sopicki

Re: Engine temperature has creeped higher over time

monty23psk

Re: Engine temperature has creeped higher over time

sopicki

Re: Engine temperature has creeped higher over time

monty23psk

Re: Engine temperature has creeped higher over time

sopicki

Re: Engine temperature has creeped higher over time

monty23psk

Re: Engine temperature has creeped higher over time

sopicki

Re: Engine temperature has creeped higher over time

mmkale

Re: Engine temperature has creeped higher over time

sopicki

Re: Engine temperature has creeped higher over time

monty23psk

Re: Engine temperature has creeped higher over time