Hello all, been battling an overheating 88 240. It doesn't matter if it's 0 degrees or 100 degrees out (more so when hot), if I'm at idle and the ac is on the temp gauge creeps up. Once I turn the heat on, and/or get up to high way speeds, temp sits at a comfortable level.

Heres what I've done:

Fan clutch (pulled from a junkyard clean low-mileage 740 with body damage)
thermostat (atleast 3 in the last 2 years)
radiator flush & fresh coolant
temp comp board & temp gauge
water pump (within last 2 years)

Motor has good compression and plenty of power (for a 240) so I don't think it's a head gasket issue, but I can't seem to figure it out, and it's really starting to bug me.

On a side note, AC does not really work. Recharged the system, which didn't help, and clutch on compressor operates, but no cold air inside car.

Final question: There is a flimsy black plastic fan in FRONT of the radiator behind the grill. Is this an electric fan that is suppose to be on? I have never seen it turn, but of course I can not look at it while I'm driving (although if I could find a brave candidate I'd check).


Thanks!

 

That fan which is located in front of the Air Conditioner condenser should only run when the A/C is on. As for the over heating, I'm not sure. About where does the temp gauge needle point to? Does it get in the red?

 

well, if the AC isn't working, then why do you turn it on at all?

was this AC system converted to R134a ? has it been leak tested ?

as piv15 said, the electric fan only comes on when the AC is running, and only if its hot enough.

waitaminute. an 88 is virtually identical to an 87, and our 87 has no electric fan at all, they were added later. that means if this car has a van, it was added by someone. Looking at a 1991+ diagram, which DOES have an electric fan, that fan is on a relay, which is enabled by A) pressure sensor on the condensor and B) pressure sensor on the receiver-dryer and C) compressor on.

so, IF your added fan was wired up like it was in a later car (big IF!), then it would only work if their was sufficient AC system pressure but not too much. the compressor itself will only come on if there's adequate dryer pressure.

 

Indeed... why run an air conditioning system at all if it doesn't work. I do remember when I first got my car about a year ago that the compressor was bad. Made horrendous noises, and bogged down the engine.

 

in fact, I recommend disconnecting the compressor if the AC system is non-functional. running it with insufficient freon will fry it. We had one seize up and burn the belt, which knocked out the power steering.

 

Some additional details and answered questions:

It has the typical pre-93 water pump driven mechanical fan

It has a fan of some sort in front of AC (i assumed radiator) I did not see it turn on when I had the AC on and let it idle for some time. (car over heated in this period)

Temp gauge DOES NOT and HAS NOT gone into the red, reaches the "10 o' clock" position.

I had the AC because when I tried re-charging it this last weekend, I found out it had already been converted and had freon in it, just didn't blow cold air

AC compressor works, but doesn't ever seen to turn off. I turn the AC switch all the way around to 0, but AC compressor doesn't stop engaging. Compressor does not make horrendous noises, and does not seem to bog down engine.

 

ac system was converted to r134 and has been leak tested, because it had sufficient freon in the system (i have been driving car 5 years and checked it first time this weekend) and I saw remnants of the green dye when I took the pressure gauge off.

as I said in previous post, compressor doesn't ever seem to shut off.

 

ok. your car has been modified. the electric fan wasn't added until 1991, and at that time, they also changed the heater control panel. so I have no idea how your car is wired, my diagrams show how a 88 and a 91 was wired from the factory. maybe someone put 1991 parts in your car. maybe they just cobbled up the fan. on a 1991, the fan is controlled by a relay that comes on when the compressor is on.

a 91+ has a seperate toggle switch for the A/C, while a 88 has a **** that clicks in the OFF position and acts as a thermostat for the A/C

on either of these cars, a signal comes out of the AC relay in the dashboard thats +12V when it wants the compressor on. this goes to the low pressure switch on the radiator (88) or reciever/dryer (91), and from there to the compressor solenoid.

some tests...

1) disconnect the pressure switch. use a volt meter to check one side or the other against ground when the car is on and the AC is turned on. if one of the pins is +12V, and goes off when you switch the AC off, then the dashboard controller and relay is working. if not, fix that.

2) bypass the pressure switch (jumper both pins of the plug that goes onto it). if the compressor comes on then the pressure switch is bad or you have low/high pressure (I forget which).

3) run a jumper wire from battery + to the compressor solenoid. if the compressor kicks on, then work backwards, you missed something.

 

Thanks a lot! I will try some of those test today. I find it unusual that my car was modified, as it came from a one owner family and they kept almost 100% of the repair records up until about 2003. I may give them a call back and ask them what has been done with the AC. But, I know that my 89 wagon doesn't have that fan, so like you said, it HAD to of been modified. Hopefully I can figure out what they did and solve the AC.

Do you think this issue will have anything to do with the overheating?

 

As for the over heating, 10 o'clock doesn't seem bad. I know my temp gauge is everywhere, (usually on the low side.) My father said that when they had a 240, during the summer time the temp gauge was everywhere. Every now and then mine reaches that level, but settles back down.

 

Yeah, I have the same issue on my 1980 with the temp gauge going everywhere, had the problem on my 88 for ages, and had this problem on my 86 wagon years ago. Never had a problem with my 89 240, or any of my 740s. I would just like to someday figure out what causes this and how to fix it. I did finally order a IR temp gun off ebay this week, so hopefully when that comes in the mail I will be able to confirm if/how much the engine is actually overheating.

Speaking of the IR temp gun, what is the most optimal point to measure the temp from, and what range should I be comfortable with? At which point should I be worried?

Thanks again.

 

Problem fixed. The wiring was kinda iffy, and I repaired a ground, and replaced the relay and the electric fan turned on! It did not have the normal noise suppression relay for the aux fan, instead it had a standard bosch 12v 30 amp relay, which I replaced with a bosch 12v 20 30amp relay because that was all I had on hand. Seems to work OK. I let the car sit and idle for a good 10 minutes, and it did not overheat. Took it out for a drive, and again it did not overheat. When I got back home and sat in the driveway, the temp creeped up slightly, but I depressed the gas pedal slightly and the temp came back down and stayed down. Once it hits 95+ degrees outside, I'll really be able to test it.

Also, AC kinda works, it's not ice cold it's more like "luke cool" but it is doing something. Having the fan on certainly improved conditions.

Here are some pics of my findings:

 

Woo! That home-made wiring job. Well its good it cools slightly. I'm battling a bad switch issue on my A/C. The switch on the Receiver dryer is shot on my car, so it must remain jumped. This makes the A/C run constantly and freeze.

 

You can get the low pressure switch for around $30. Get it before you ruin your A/C compressor.