1994 940 cooling fan never comes on

[Jebus]

Originally Posted by Free940

The link didn't work, but I will find it. Thanks!

oops sorry its fixed now if not had any luck

[aardvarkash10]

Originally Posted by Free940

It wants to boil over so I shut it down. What would you recommend my next step be?

What do you mean by "it wants to boil over"?

The 940 runs a prety high pressure cooling system so if the cap and system are holding pressure, the boiling point is shifted to about 110 degrees C.

On top of that, the radiator is mucho efficient. Depending on ambient temperature, the car might idle all day without the fan coming on.

You really need to check the temperatures using a good quality thermometer. You may be trying to fix a problem that doesn't exist.

[Free940]

Originally Posted by aardvarkash10

What do you mean by "it wants to boil over"?

The 940 runs a prety high pressure cooling system so if the cap and system are holding pressure, the boiling point is shifted to about 110 degrees C.

On top of that, the radiator is mucho efficient. Depending on ambient temperature, the car might idle all day without the fan coming on.

You really need to check the temperatures using a good quality thermometer. You may be trying to fix a problem that doesn't exist.

I probably shouldn't tell you this..

It seemed like it was running hot. One of the hose clamps was slightly loose and after the engine ran quite a while, steam was whistling out.. I removed the reservoir cap and the coolant boiled out. My gauge never went past the middle though. I thought the gauge was defective. Maybe it is. (?) I have gained knowledge on this forum and want to regroup and try a few things. I have a laser thermometer ordered.

I'm thinking that maybe I had air in the cooling system and it was not completely full of coolant. I had changed the water pump and let the coolant drain out. I don't see how the sealed system could be refilled by just pouring coolant into the reservoir. Next time I fill it, I am thinking of removing the plastic plug on the top right of the radiator. Putting it back when coolant comes out. This might ensure there is less air in the system, although I realize that the thermostat needs to open.

I do know for a fact that the dual speed fan relay was bad before I replaced it.

Maybe this is all nonsense..

[aardvarkash10]

aaaah.

Volvo's, in my relatively short experience, have a way of teaching you lots!

Boyle's Law is one of those things. It states (and I paraphrase here for clarity)
"if your radiator cap is on and engine cooling system becomes pressurised, taking the cap off will result in the sudden expulsion of steam, water and stuff that hurts."

Pretty sure, but not positive, that your car has a grey cap. That holds about 0.75 bar or around 12psi in the old money. This means that the water in the system will only boil at about 115 degrees C, or around 240 degrees F.

This is considered a Good Thing. The hotter we can run the engine, the more efficient it will be, but also it gives a good wide range of tolerance for the cooling system AND means we can transfer more heat away from the engine when we need to because the difference between the coolant temperature and the ambient air temperature is greater.

When you take the cap off, the pressure drops to atmospheric, and so the water boils at 100 degrees C, 212 degrees F.

Fcuk yeah, physics like a boss.

Yes, definitely open the bleed plug when you refill the system. Fill, bleed, close the bleed plug and fit the pressure cap, let the engine get up to temperature, switch off, let it cool (an hour or so), refill the system to the marked level in the reservoir, refit the cap, job done.

Check with your thermometer. I suspect you have mildly over-reacted. Better than not reacting though eh.

[Free940]

Bleed plug! is that what that is?

You know, I looked in my manual to find the procedure with no reference to that plug. I read some other threads that mentioned it but not to bleed the system. I will give it a go. This is my first vehicle I have owned that doesn't have a radiator cap.

I don't see how this engine could run long periods of time without the fan eventually coming on though, but as you say, it depends on the ambient air temperature. Yes, I have the 0.75 bar grey cap. So without a gauge (broken?) or thermometer (on order) , the temperature is normal as long as this cap doesn't release pressure, which would indicate over heating?

Of course my gauge will never work properly unless the system is full of coolant. I suppose I could test it by powering one leg and grounding the other to see if it moves all the way to the right.


Thanks for your patience and explanations. I will at least clean all my sensor connections and give it another go.

[griston64]

When I renewed my coolant last year I just drained it all out via bottom hose. Removed thermostat housing and flushed with cold water from the hose. Fitted everything back and refilled via the header tank. I then ran car with header tank cap off and topped up as it warmed up. Did a couple of burps by squeezing top hose and Bob's your Uncle.

Don't forget to fully open heater when you drain as well

[Ian21401]

Originally Posted by griston64

When I renewed my coolant last year I just drained it all out via bottom hose. Removed thermostat housing and flushed with cold water from the hose. Fitted everything back and refilled via the header tank. I then ran car with header tank cap off and topped up as it warmed up. Did a couple of burps by squeezing top hose and Bob's your Uncle.

Don't forget to fully open heater when you drain as well

Ditto to above and Ash’s comment re coolant boiling out if you remove the expansion cap when system is hot and pressurised.

Just refilled my cooling system by replacing the coolant that I had removed to fit a new thermostat. Ensure heater control is set to fully hot when refilling to permit full circulation of the coolant to minimise any air locks. I’ve never used the “bleed cap”.

[Free940]

As soon as I got home, I rushed out to the Volvo and shorted the wires from the temp gauge sensor together, turned on the ignition.. It went all the way to the right!

I reconnected it.

I then filled the reservoir with water (I didn't want to use antifreeze in case there were problems.) I then ran the engine for about 30 or 40 minutes.. the gauge went half way and stopped. The outside temperature in South Florida is 84 degrees. I watched the gauge and it never really moved. Then after another 15 minutes, the fan kicked on. It ran for about 20 seconds and shut off.. The fan repeated this every 5 minutes or so.

Everything seems normal, although the engine did suddenly shut off a couple times before it got hot, when I first started it. Like the key was turned off. It restarted right away though. It has never done this before. I don't know what that was all about. The idle might be a little low (about 800 RPM's).

I also can hear some slight ticking like one the valves needs to be re-shimmed.

Did I mention that I am a happy camper!!??

I pulled some codes as follows:

Side A: #1 no flashes, #2 111, #3 111, #5 no flashes, #6 111,
#7 no flashes

Side B: #1 no flashes, #2 122, #3 no flashes, #5 111, #6 no flashes,
#7 no flashes

I will try and find the meaning of these codes.


EDIT: #2 122 = Either I have a bad air temp sensor or it's making a bad connection:

[griston64]

Originally Posted by Free940

As soon as I got home, I rushed out to the Volvo and shorted the wires from the temp gauge sensor together, turned on the ignition.. It went all the way to the right!

I reconnected it.

I then filled the reservoir with water (I didn't want to use antifreeze in case there were problems.) I then ran the engine for about 30 or 40 minutes.. the gauge went half way and stopped. The outside temperature in South Florida is 84 degrees. I watched the gauge and it never really moved. Then after another 15 minutes, the fan kicked on. It ran for about 20 seconds and shut off.. The fan repeated this every 5 minutes or so.

Everything seems normal, although the engine did suddenly shut off a couple times before it got hot, when I first started it. Like the key was turned off. It restarted right away though. It has never done this before. I don't know what that was all about. The idle might be a little low (about 800 RPM's).

I also can hear some slight ticking like one the valves needs to be re-shimmed.

Did I mention that I am a happy camper!!??

I pulled some codes as follows:

Side A: #1 no flashes, #2 111, #3 111, #5 no flashes, #6 111,
#7 no flashes

Side B: #1 no flashes, #2 122, #3 no flashes, #5 111, #6 no flashes,
#7 no flashes

I will try and find the meaning of these codes.


EDIT: #2 122 = Either I have a bad air temp sensor or it's making a bad connection:

Your idle should be 750 rpm depending on what engine you have. 800 isn't low it's possibly slightly high

[aardvarkash10]

Originally Posted by Free940

As soon as I got home, I rushed out to the Volvo and shorted the wires from the temp gauge sensor together, turned on the ignition.. It went all the way to the right!

I reconnected it.

I then filled the reservoir with water (I didn't want to use antifreeze in case there were problems.) I then ran the engine for about 30 or 40 minutes.. the gauge went half way and stopped. The outside temperature in South Florida is 84 degrees. I watched the gauge and it never really moved. Then after another 15 minutes, the fan kicked on. It ran for about 20 seconds and shut off.. The fan repeated this every 5 minutes or so.

You see Grasshopper? Patience...

Originally Posted by Free940

I also can hear some slight ticking like one the valves needs to be re-shimmed.

"Blip" the throttle to get the engine up to about 3,000rpm and then back to idle. Does the sound of clicking stop when you close the throttle?

Originally Posted by Free940

I pulled some codes as follows:

Side A: #1 no flashes, #2 111, #3 111, #5 no flashes, #6 111,
#7 no flashes

Side B: #1 no flashes, #2 122, #3 no flashes, #5 111, #6 no flashes,
#7 no flashes

I will try and find the meaning of these codes.]

The could be old codes. Take fuse #1 out of the fuseholder for 1-2 minutes, then replace it. This clears any old codes. Run the car and then recheck the codes.