The fan clutch would spin freely after shutting down a warm/hot engine, so I replaced it with a new Aisin (Volvo OE) unit. The temp still indicated high.

Next was the water pump. No signs of leaking, but the bearings sounded worn and did not turn smoothly. I replaced it and the top/bottom hoses with Volvo blue box parts. The engine bay sounds better now, but there is no change in the temp indication.

Next I borrowed a friends IR temp reader since I don't know I can trust mine. I put a piece of black tape over the thermostat housing and I get a reading of 185-190 degrees. This seems about right.

In summary, I've installed new Volvo OE parts:
- coolant temp sensor
- fan clutch
- coolant
- upper and lower hoses
- water pump
- thermostat (twice)
- temp compensation bypass kit (IPD)

I've also cleaned the radiator exterior.

At 185k, all the replaced parts were original and needed to be done. I plan to keep this car for as long as possible.

If the temp reading from the IR scanner is correct, I think I need to look at the temp sensor, temp gauge and the circuitry in between.

Thanks.

Quick update:

I followed the recent suggestions:

1. I removed the thermostat, ran the vehicle for 30 min around town. The temp stayed mostly at 7-8 and once got close to 9, but never went over 9. I picked up a new thermostat from my Volvo dealer.

2. I installed the new thermostat (87 degree stamped on it) with the vent at the top, and the temp indication goes right back to where it was with the previous thermostat so I don't think that's the issue.

3. I also dropped the thermostat in a pot of boiling water and then let it cool down to see where it closed. It seems to happen at about 190 degrees.

4. I removed the electric fan again, and thoroughly washed the radiators from the engine compartment out. They look great. No change in temp indication.

I think the next areas to inspect are the pump and radiator. My guess is that the radiator is almost new. The aluminum is shinny and the plastic sides look great. The fins are in terrific shape as well. The pump on the other hand look pretty old. I want to have one on hand when I do the inspection so I can make the swap if needed.

Thanks again for all the suggestions and stay tuned for an update next week.

Hmmm. I'm reminded of my temp gauge reading high after I replaced the failing cluster voltage regulator. I was told it was supposed to be a 10V regulator, but the original seems like it had to be lower. Both the fuel gauge and temp gauge read higher.


Assuming you have time and money to throw at the problem:

This is what I recommend doing:
Clean the radiator fins - clean the AC condenser fins too. Soap, high velocity water, etc. Spray inside to outside. Backflush all the accumulated junk out. Water didn't hurt my aux fan, and yours is exposed to rain, so you can assume it will survive.

Pull the thermostat. Boil some water, drop it in, watch the temps as the water cools, and note when it starts to close and when it finishes closing. (cooling might be faster than heating, do it either way).

If the thermostat is good:
Check the water pump. Don't try to check it, remove it or shine a light in the outlet (pointing towards the passenger side) and look at the fins. Are there still fins? Did they corrode away? The original pump on my 90 740 had 1.4 fins left in it at about..... hm... 180k miles I think, which led to constant cooling problems. If you can't see the fins (an inspection camera would be perfect), pull the pump.


My intuitive guess is the pump is old and has a lot of its fins missing. Something's not working - the thermostat is new, the radiator is new, the coolant I'm assuming is new and at the correct concentration for the ambient temperatures and humidity you have, and the pump is in unknown condition.

You can try shorting the aux fan switch to make it turn on. If that helps drop your temps, maybe you have an excessively slipping viscous fan clutch, but those usually fail in a locked mode, not a slipping mode. The car shouldn't normally run the aux fan, but it could be a diagnostic tool. You already mentioned that running the heater drops the temps, and that should tell you that you're getting insufficient coolant circulation or heat transfer.

My money's on the pump. Make sure you put the heater tube seal onto the tube, not into the pump. I did the job 3 times in one night because of that stupid thing.



You can also check to see the rating and function (sort of) of your reservoir cap. If it's venting too early or is an incorrectly low pressure cap (identified by color of cap with 3 pressures.... I think 75, 100, and 150 kpa and white, grey/black, and green, no idea which is which). The easiest test is probably replacement, but I found that the plastic ball in the pressure relief on my old cap was crusted up. Popping it loose restored it to working for a while, but I replaced it eventually. There's also a small valve that can pull into the reservoir through the cap - this is the negative pressure relief. Both should move with a bit of pressure. Be gentle with the negative relief.

Hope that's not too much at once. Oh, and the aux fan is not meant to run unless the car exceeds a certain temp (temp sensor in the radiator) or the car is running on max AC and.... I think a pressure switch is tripped.

Good Luck!

you wrote:

Picked up 240: temp gauge shows low temp, 7-8 position
Replaced broken thermostat (stuck open) with Volvo OEM and replaced coolant
Temp now reads high (10-11 position)

1. remove thermostat and run the engine. if it measures 7-8 on the gauge you found your problem

2. if nothing happens for the better:

use a garden hose from the engine side and blow the dirt out of the radiator fins

test engine, better..you're done, not better

with no thermostat present i would recheck the sender you installed to make sure its good, the temp gauge could be suspect but then it would have measured 10-11 with no thermostat before you intervened so this is not likely.

Quick update. Any pointers are appreciated.

- I purchased a infrared thermo scanner. Not sure I can trust it since some known temps are 'off' by about 10%. My thermostat housing reads anywhere between 165-180 after a long drive.

- the in-dash temp gauge does show a drop when the temperature control moved to max heat. De-calcification was mentioned. Any good pointers? I'm willing to replace the radiator even though it looks new if that will be the best solution.

- I believe the thermostat is installed correctly

- how would I know if the pump is doing it's job? I don't know how to measure flow.

Thanks again for the suggestions.

Thank you for all the suggestions. I think it's time to directly measure the temperature before I try figuring out which part is causing the high temp reading. Stay tuned...

Thanks again!

Thermostats come in 3(?) different temp settings. Perhaps you put in a hot one.

Does the temp needle drop if you turn on the interior heating? If it drops and stays down you may need to decalcify your system.
--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

Here are some thoughts to help you narrow down, or eliminate, possibilities:

First, glad you bypassed the TCB ("IPD bypass kit"), as that's always my first suggestion.
But I also always initially suggest determining whether or not temperature is really a problem -- remember that you suspected your gauge when you tested the gauge's wire as well as its sender. The only true way is to use a IR "remote" thermometer (you point a laser at something and get its temperature on an LCD screen) -- they're pretty cheap nowadays, around $40 give or take. You scan the cover of the thermostat housing to get true coolant temperature just before it gets to the radiator (the hose is not as good a heat conductor, so you should scan only the metal housing for the best indication).

Okay, assuming it's really running too hot, consider the question of the fan clutch. First, remember that it only works at low speeds, in traffic -- it contributes *nothing* to cooling when you're driving at highway speeds -- so if the problem is only at slow speeds, it could be the clutch; but if the problem is always happening at both high and slow speeds, then look somewhere else.

I find it noteworthy that you replaced your car's thermostat right away (because it ran "cool" when you first bought it because of a stuck open thermostat), and afterwards it ran hot. Have you considered it possible that your new thermostat is defective? With all your efforts and expense put into solving this, maybe invest the small price of a second new thermostat? Also, did you install the first one correctly, rotating it with the air bubble bleeder at the highest point? And was it a good quality thermostat, or even the correct one?

Finally, the issues of a bad radiator as well as a bad water pump comes to mind because you wrote that it shows when you accelerate hard or climb a long hill. I have two '93's like you, with the TCB bypassed, and I never observe a change in temperature when I do that, which is often. The only time I see any even slight increase in temperature is when I'm running the A/C, so it sounds like your cooling system just cannot handle the dissipation of a lot of heat, which of course points to the radiator and/or the water pump.
First thing is to be sure the radiator's external fins aren't blocked (e.g., bugs). Hose it but be gentle -- a strong spray (e.g., car wash wands) can bend the fins -- it's a lot safer to use a compressed air hose. Blow it from the back to the front (opposite to the way insects were jammed into it).

You can't tell if the water pump is bad just by looking at its appearance -- corrosion could have reduced the vanes of the impeller to rubbish so that it can't propel enough water (and let's not forget about fan belts that are letting the pump slip -- they don't always reveal looseness by squealing).
And the radiator might be shiny indicating newness to you (although I've never heard of a "shiny" radiator for a Volvo, as they're supposed to be black when they're new); or more likely some recent reconditioning, and that might have been done poorly. I know that you can't easily look at the core (as you could in the old days with radiator caps on top), but there is a way to have some indication: remove the shroud and use the IR thermometer to scan the core (from the engine side, as the A/C condenser is in the way on the other side) for hot and cold spots that mean blockages.

Good luck.

Had the same issue with my 85 245 replaced water pump, thermostat, hoses flushed cooling system the works. No change, gauge still reads 10 to 11 on freeway.. Took it to my smog guy and had him sniff for hydro carbons... Bingo hydro carbons were very high.. That means leaky head gasket even though there are none of the usual signs of a blown head gasket... Hot gases escaping into cooling system will cause hydro carbons to show up in coolant .. Have your smog shop sniff your coolant bottle ... I did my head gasket and valve job and temp is perfect.. Read FAQ 700/900 you will see an article there...Hope that helps

In my experience, '93s are just about at that age where all the original cooling system components may still be present, and if so - ticking time bomb. Every piece of my cooling system failed in quick succession last year. I often had temps around 10 o'clock as well, because of the reduced cooling efficiency of the radiator. Watch it carefully.

You might also want to replace the water pump if you do not know its age. The GMB pumps are cheap, and I quite like them. Sounds like your gauge is working properly.

Fan clutch - maybe, but unlikely, I think. Not on a '93.