Okay so my girlfriend has a 94 940 non turbo we are having some problems with the cooling system first time it overheated we seen coolant coming out of the front of the block by the water pump so we went an got a new one along with a thermostat ran fine for a few days then the aux fan started to stay on so we unplugged it now iv done this in my Honda an Acura in the past an when I was in traffic I would just watch the temp gauge so I told her to just watch it in traffic well last night we went out an her radiator cracked on the driver side an leaked coolant faster then we could put it in now what could cause this to happen

Note we took the thermostat an did not put one back in her Volvo only has 130k on it

 

So, obviously you need a new radiator, for starters.
Then, your car was getting hot for some reason which you have to diagnose. Hopefully you didn't overheat it too much.
I'd take a compression test before anything else...

 

Yeah that was my next thing to do just got the radiator in the car today I was just wondering if Volvo's had any major problems with the cooling system cause I know Subaru's do but it kinda looked like it was time for a new one seeing that is was made from plastic on the sides kinda made me think you would have to change them more often

 

volvo cooling systems are generally very long lived as long as you use suitable antifreeze, and change it every few years. real volvo water seals won't leak, aftermarket ones are less reliable, and frequently need RTV or whatever.

my 745T had a mild overheat incident before I bought it (price discounted accordingly), it was seeping a small amount of coolant out head gasket near the #3, #4 exhaust ports. after 6 months it finally blew, and I had it towed and fixed properly.

I noted the previous owner had the radiator replaced and the replacement Nissen (OE) failed and needed replacing on warranty. meh.

when I replaced the radiator on our '87 240, I got one of the custom made brass ones IPD used to sell. it was a little larger than the original but fit right in its place and has worked great, that car drives well in 110F weather (too bad it doesn't have an AC anymore, hahaahahah).

 

Assuming you have no water in the oil and no head gasket leak then the new rad. should fix the problem. Also replace the thermostat with the low temp one (165* +-) . I would flush the system with water only and see what comes out. Do a power flush if possible. As to the plastic tank rads I don't find them to be a problem. I have replaced 2 brass tanked rads over the life of our 89 740 and the 3rd and last was changed at 210K. We now have 334K on it and cooling is fine (center of gage) in all temps. I'm just waiting for the head gasket to go but hopefully is continues to hold. Good luck and keep us posted.

 

the head gasket is fine no water anywhere an not blowing white smoke no coolant in the oil so thats all fine we did the power flush at the shop last night an got dirty water is all the new thermostat i got from autozone didnt work so i went to carquest (where i get all my parts) an it all works fine now but the AUX fan still dont work so now its time to change the relay an hope that fixes the problem but as of right now everything is working good it doesn't overheat anymore

that night it did the an rad blow the temp gage was right no the mid tho so im not sure what that means if anything

 

instead of just replacing the relay, why not do some tests on it?

the 1994 940 schematics show you have a dual speed fan, and thats a double relay.

first, the relay is powered directly off the battery via a fuse. verify that pin 1A of the relay socket (with the relay unplugged) is powered at all times (this is unswitched).

at the relay socket, pins 1B (blue-black) and 2B (white-black) are the control lines, they should be floating, not ground when the car is off and cold. if either of them is grounded, the fan is powered at the corresponding speed. unplug the relay, use an ohm meter between the corresponding relay socket and ground and check to see if they are grounded.

pin 1B can be grounded by either the the green low pressure sensor in the condenser manifold, or pin 10 from the LH2.4 ECU (*).

pin 2B can be grounded by either the brown high pressure pressure sensor in the condenser manifold, or pin 11 of the LH2.4 ECU (*)

now, if neither of those pins is grounded, AND your fan comes on as soon as you plug the relay in, then definitely, you got a bad relay. if one of those signals is stuck to ground, I'd use the ohm meter directly across the corresponding sensor (with the wiring unplugged) and see if the sensor switch is stuck closed. if so, you need to replace that sensor, not the relay.

now, if your fan isn't working at all, disconnect one of those sensors, and manually short it at the connector, the fan should come on (with the relay is plugged in). shorting the other sensor shoudl make the it come on at the other speed.



(*) if you have Regina EFI, then its a little different, instead of the ECU signals there is a temp switch plugged into the radiator)