Overheating!! 1988 Volvo 240
 

Hello,

I've got a 1988 240DL wagon. Here's my backstory

1. Radiator cracked. Replaced radiator. Ran beautifully. Temp gauge way low, like 1/4. Everything great.

2. Coolant started leaking. Blown water pump seal.

3. Replaced water pump seals and gasket, replaced thermostat. No coolant leak, at all. Re-filled, idled with cap off for a few minutes.

4. Test drive! Drove about 10 miles, temp at middle, ok. Suddenly it started overheating!

I suspected air traveling through the system. So I went back to my neighborhood and ran the engine with the coolant reservoir cap off for a good while because I know air in the system can haunt you. I ran the engine with the cap off for way longer than necessary. Temp calmed down. Drove like another 5 miles with the cap off. No way there's air in the system. Coolant is not leaking at all, so I can't imagine there's air sneaking into the system either.

Once I seemed to get the temp calmed down I drove another 10 miles and it was at mid, but as soon as I got back into town and, for example, went up a tall hill or something, temp went STRAIGHT to the top again! I am totally stumped and getting frustrated. Worth noting I have enough oil, car drives fine. No low fluids. Can't imagine there's anything else wrong, problem started with the cooling system, persist with the cooling system.

What's going on?

did you use a chinese thermostat ?

Authentic. From the local independent shop.

I've never had any issues with air in a redblock, it all collects in the overflow bottle, top it off and its always been good to go.

I think I'd get or borrow a IR thermometer and read the temp of the block, the radiator hoses, and the radiator top and bottom next time its 'overheating'.

I don't have a source for one of those. Is there anything else I can try? Should I try a diff thermostat?

IR thermometers are $20 nowdays...
BAFX Products (TM) - Non Contact - Infrared (IR) Thermometer (-58F - +1, 022F) - W/ Pointer Sight - BATTERY INCLUDED!: Science Lab Digital Thermometers: Amazon.com: Industrial & Scientific

if the thermostat is opening and your water pump is moving sufficient water, the top hose to the radiator will be hot, as will the radiator.. the input side of the radiator should be warmer than the output side, and the return hose to the engine block should be considerably cooler than that top hose.

"if the thermostat is opening and your water pump is moving sufficient water, the top hose to the radiator will be hot, as will the radiator.. the input side of the radiator should be warmer than the output side, and the return hose to the engine block should be considerably cooler than that top hose."

Just tried again. When it over-heated, everything was hot. Top hose hot, radiator warm to touch, bottom hose hot, return hose hot.

Seems like... maybe a water pump problem?

Hi Pierce,

This morning I tried starting the car completely cold. Fired right up, but oddly enough, the temp gauge started moving right away. It usually doesn't budge until the engine has been on for about 5 minutes or 1/4 mile or so.

It climbed slowly to middle-then to about 3/4 of the way up. I popped the hood, and the top radiator hose was completely cold, the lower hose was luke warm, and the return house in the back of the water pump was cold. Does this mean my temp gauge is reading incorrectly and I should look into the behind-the-dash fix here? I'd like to add that over the years, this has happened on and off, but usually the thermo goes back down. I always attributed it to a stuck thermostat, not a problem with the gauge itself.

Thank you,

Personally, I would do the compensation board bypass mod in the instrument cluster..... but as Pierce suggested, get a $20 IR thermometer (my local home improvement stores usually have them for $30) and do some tests with it as well. I know that many people can do the feel test on the hoses and can tell a difference, but I have never had the sensitivity to be able to feel good about it... (everything always feels hot to me).. It is very reassuring to have some real numbers on the temperature... And you will find a lot of other uses for the thermometer.

it does sound like your temp sensor, or the gauge itself is fubar, and this certainly could be the fault of the $#@$# compensator circuit.

Thanks Pierce. It does seem weird that the gauge would start to go up IMMEDIATELY after starting that car, when everything is pretty much still cold to the touch. Should I try that bypass fix?

your 92 may no longer have the seperate compensator card, making the bypass fix harder.

for background, this stupid $#$#@# 'compensator board' is designed to center the needle if the car is anywhere near normal temperature, this reduced service calls by neurotic owners freaking out that their car ran hot uphill and cool downhill. it reduces the needle to something akin to an idiot light.

Pierce, my 240 is a 1988 model. I've been into the instrument cluster before. I repaired my odometer last December. This fix would be easy for me, and cheaper than buying a IR thermo :) I'm gonna give it a shot after work, I have the URL for the instructions, they seem incredibly simple.

Thanks!

I know you suggest I buy a thermo and check temps, but what observations are possible and what conclusions would I draw from them?

Thanks.

the IR thermo would confirm your engine isn't overheating. seeing the gradient across the radiator would indicate the radiator is flowing well.

of course, an overheating engine s/b OBVIOUSLY too hot, smells like burnt oil instead of just hot oil. my experience is, just about when the needle pegs, you start pinging something fierce (and that's when you definitely should shut it down!!).

The engine always performs the same, it's just the gauge that goes up. It doesn't smell different when the gauge is up either. On the highway over the holidays it would randomly go up toward the red, but the engine always ran the same. I am suspecting the gauge itself is reading incorrectly. We'll see.

if the engine were really overheating, could you even touch the hoses without burning yourself?

My 91 still had a separate temp comp board--I think they did that on 240s right up to the end. and the temp comp bypass was one of the first things I did on my car. however, for $20, I think i'm going to get one of those IR thermometers... I've always been curious about various temps on that car, and that could be a super-great tool otherwise.

Hey everyone,

I pulled the temp comp board, jumped the terminals, and re-installed everything and it stopped overheating.

Temp gauge floats between half and a little above half. That's probably to be expected I imagine.... I do need new belts btw and I'm sure the tension is not quite right, also I ditched my fan shroud.

Thanks for all your help!

the fan shroud, and the bottom engine cover both greatly aid in cooling.

Something about the new radiator and my engine, the fan grinds against the shroud. That's why I removed it. The car was salvaged at some point before I owned it, I think maybe it threw some things off.

The fan shroud is an integral part of the cooling system. Without it you might as well ditch the fan since not having the shroud really reduces the amount of air the fan pulls through the radiator. However, the fan and shroud really come into play when stopped or at very low speeds.

If the fan scrapes the shroud, you might want to check the motor mounts to make sure they aren't broken. Broken mounts will cause the engine to shift around and possibly cause the fan to scrape.