95 Taurus Overheating when A/C on

My 95 Taurus is overheating (gauge above "L") only when I have my A/C on. The only part on the cooling system that was replaced was the radiator. I bought an original Ford radiator. To prevent further increase of coolant temperature, I switched off the A/C and then the temperature will go down.

Can anyone tell me what is causing this phenomena?

Thanks for your help.

Mbana

I would suspect that either the cooling fan is not plugged in or the motor is bad. When you turn the A/C on, verify that the cooling fan runs. If not, then determine if the fan is getting power using a test light or multimeter.

-Rod

Thanks for your suggestion.

The cooling fans are working alright when I switched on the A/C. I know that the fans have multi speed seetings and that the temperature sensor controls that. Could it be that the fans speed is malfunctioning?

Thanks again for the help.

MBana

"Could it be that the fans speed is malfunctioning?"
Me thinks they have two speeds; wide open & stop, so check the connections like Rod said. Reason I say that is 'cause in the morning I turn the AC on with the engine stone cold and the fans take off and sound wide open to me just a' gittin' it. Matter a' fact, never heard them run any speed but wide open hooked-up. Mine's an 03 and maybe yours is different.

Is the condenser clean not plugged up with bugs, etc? When you turn on the AC the condensor heats up to about 170 - 180 degrees and the air passes thru the condensor before it goes to the radiator, so theoretically we cool the radiator/engine with 170 degree air. With the AC off you are using ambient air temp to cool the radiator, so make certain the condensor fins are not reducing air flow to the radiator.

If you decide to clean the condensor fins be careful not to use to much power wash pressure and keep the nozzle at a 90 degree angle to the fins. You hit the fins at an angle with the water presure and all it takes is a little pressure to bend the fins over, then you only serve to complicate the problem. I assume the new radiator does not have a lot of bent over fins.

If the thermostat hasn't been changed in five years I'd invest in a new type SuperStat made by Stant.

"The power element of SuperStat® is comparable to those used in heavy-duty trucks. Its actuator piston is 25% larger in diameter than our standard thermostat and 56% larger than competitive product. This larger piston delivers 1 1/2 times the power of our standard thermostat and almost 2 1/2 times as much power as the competition for enhanced durability and longer life."

Stant claims they work better and allow a LOT more coolant flow and been meaning to put one in our Taurus and Grand Marquis and think I'll put it on my 'Honey Dew' list of things- to-do this week end.

If the coolant is clean, good air flow thru the radiator and the t'stat is working right, water pump is good and belt not slipping, hoses good and don't collapse, reservoir cap is good and holds the right pressure, . . . . I'm stumped.

Change the thermostat - This pesky little component is a frequent cause of overheating. If your problem is sudden and severe, it may well be the root cause. Check out our tutorials on diagnosing the problem (http://www.jonko.com/forum/tutorials/engine/circulation.htm), and replacing your thermostat (http://www.jonko.com/forum/tutorials/engine/thermostat.htm) for more tips.
Check your circulation - Another frequent contributor to overheating. If the thermostat doesn't stop things up, your water pump might. Check out your circulation here. (http://www.jonko.com/forum/tutorials/engine/circulation.htm)
Give 50 percent - Incorrect water to antifreeze mixtures can cause your auto to overheat. A mixture that is lean on anti-freeze is often the culprit when the overheating is consistent.
Check for Slippage - Drive belts around the water pump can be another source of headaches. Even slight slippage in this area can lead to engine overheating on long trips and at high speeds.
Look for Leaks - Not to state the obvious, but look for any obvious leaks. Tell tale puddles beneath your car are a sure sign something's awry. Check that all your hose clamps are tight and replace damaged or leaking hoses right away.
Check your radiator cap - If you have the tools to check it, make sure your radiator cap is holding pressure. At lower pressures the boil temperature is also lower causing your car to overheat more quickly.
Check for internal leaking - If you are able, check your system using a cylinder pressurizing tool. If air leaks through you can be sure your coolant will as well.
Check Your Hoses - older hoses sometimes collapse from suction and can inhibit flow at higher speeds.

Allow me to caution you; overheating is the number one cause of blown headgaskets so get it fixed PRONTO. In this case I wouldn't mess around with hypothetics and if it costs you some dough to get it fixed it will be a whole lot cheaper and much less time consuming than replacing a head gasket(s).

I believe the '95 uses a two speed cooling fan on the radiator. Huney1, since I know you like websites ( :) ), check out http://www.members.aol.com/Rod2414738/Car_Stuff/CCRM-1.jpg. This is the CCRM diagram for my old '93 SHO which shows a low speed and high speed relay, and what apparently was a two speeed (plus off) motor. I don't believe this circuit was special to the SHO.

Mbana, you are thinking of the cooling fan behind the radiator and not the blower motor inside the cabin, right?

-Rod

"This is the CCRM diagram for my old '93 SHO which shows a low speed and high speed relay, and what apparently was a two speeed (plus off) motor. I don't believe this circuit was special to the SHO." Got'cha fine Rod and I stand corrected. You're an electrical engineer and all I know about electricty is how to stick a plug in a wall and put flashlights in a battery, so that schematic is total Greek to me.

Lightning storm here and lights flickering so I'm signing off.

Replaced radiator, why? Did you or someone use a lot of stop leak? Did you flush the cooling system? Do both of the heater hoses get equally warm? Is the fan motor working? Is the theremostat sticking?

Thanks all for your reply, specially to Huney for his very in depth analysis of my problem.

Yes I'm talking about the fan behind the radiator.

Radiator was replaced because of a huge leak and my mechanic said that it coudn't be repaired or if repaired will not last long. I did all the visual inspection as you guys suggested. I noticed that the rubber hose underneath the radiator looks like swelled. I am comparing this on rubber hose on top of the radiator. I don't hear belt slipping so this could not be a problem. Radiator cap is new rated at 16psi. Coolant was new. No sign of oil mixing with coolant. No rust.

If I don't overload the engine (A/C off) the cooling system is perfect. It is only when I use the A/C that my engine overheats. Someone told me to have the car tuned up. According to him it could be timing issues. I never touched the distributor for timing since about 3 years ago.

I'll keep on investigating. Thanks again to all.

Old radiator hoses can collapse, restricting the flow of coolant. Is your car really overheating or is it just running warmer with the A/C on? Was the cooling system flushed?

This is a long shot but it happened to me on my 94 Taurus.

I put a new radiator in because my old one was shot.

Started it up everything was good and then I drove it and everything was still good.

Turned the AC on and it overheated.

There was a plug over the lower connection of the radiator and it fit internally. You couldn't even see it unless you were looking straight at the hole.

It turned 90 degrees and stuck in there and was impeding flow.

The only reason I found it was because I was going to pull the radiator back out.


Also they didnt start using the degasser tank until 96 so you might jack the car up so the front end is higher and burp the upper radiator hose.

I know it sounds crazy but air can get in that model and cause overheating even though you think you have plenty of coolant in it.

Mike
:smokin:

"There was a plug over the lower connection of the radiator and it fit internally. You couldn't even see it unless you were looking straight at the hole. It turned 90 degrees and stuck in there and was impeding flow."

I believe you're on to something there Mike and I think the same principal might apply to their overheating problem. Sounds like they've covered all the bases so it almost has to be something other than the normal places or parts we'd look at.

"Old radiator hoses can collapse, restricting the flow of coolant."
Good thought, but if the engine is at operating temp the coolant pressure should be 16 lbs preventing hoses from collapsing. Then to, you can buy hoses with a stainless steel coiled wire inside to prevent collapse.

"Is your car really overheating or is it just running warmer with the A/C on?" My 03 is a service vehicle and sometimes ambient 110F index it sits and idles for half an hour with the AC full bore and the temp gage doesn't go up at all.

I have had this on-going problem myself for years. I am once again in search of the answer. Everything has been rechecked several times-no restrictions, factory radiator, fan runs properly. The key is that it only gets hot with the a/c running. If I shut the a/c off, it immediately drops in temp.

BTW-when the a/c is set to max the fans should run at high speed, regardless of coolant temp.

Are you sure the engine coolant is actually getting hot and cooling as rapidly as the gauge would indicate? Maybe there is an engine ground cable or something that is disconnected, causing the gauge to perceive an inaccurate reading from the coolant temperature reading from the sending unit. Have you ever replaced the water pump to make sure the fins on it are fine? Maybe they are corroded just enough that the added load from the A/C cause the coolant to get hot. How about the pressure cap, is it properly pressurizing the cooling system?

-Rod

You forgot to say which 1995 engine and transmission you have. My daughter's 1995 Taurus wagon with the 3.8L engine and automatic transmission had the water pump replaced. However, this caused the timing chain cover gasket to fail, which caused a coolant leak.
Some of the 3.0L 12 valve engine blocks have been said to have sand which destroys the water pump impelers and plugs the heater core.
Different engines may have different problems, such as air trapped in the cooling system.

Are you sure the engine coolant is actually getting hot and cooling as rapidly as the gauge would indicate? Maybe there is an engine ground cable or something that is disconnected, causing the gauge to perceive an inaccurate reading from the coolant temperature reading from the sending unit. Have you ever replaced the water pump to make sure the fins on it are fine? Maybe they are corroded just enough that the added load from the A/C cause the coolant to get hot. How about the pressure cap, is it properly pressurizing the cooling system?

-Rod

Rod,

Thanks for your help. I suppose I should clarify a few things-I have a '99 not actually a '95, but this is the weirdest thing I have ever seen. I dabbled as a pro mechanic for about 2 years and have been a solid "minor league" tech for a long time.

To answer your questions, I replaced the water pump due to seal leakage about 2 years ago which did not affect this issue one way or the other. Several infrared temp readings at different locations on the exterior of the cooling system indicated that the coolant temp was in fact signifigantly fluctuating with a/c on or off. Fan operation was also verified. Pressure and level are correct

I have also replaced, then removed the thermostat to eliminate it as a contributor. Now it takes forever to generate heat in the winter. In the summer it runs just a little on the hot side, but again, no t-stat. Then if you turn on the a/c-it just goes up until it reaches the threshold to shut the a/c itself. A few days ago, it was only about 70 degrees where I live and I tried it out and even at those low ambient temp it still got hot. Lastly, I have cleaned the space between the condenser and the radiator and eliminated any bugs, dust, etc.

The car is just posessed. lol I was hoping this was a common problem and someone out there had some little known fix like overharged ac or anything.

This is driving me crazy.......:banghead:

Have you tried letting the car idle or running it at 2000 rpms while in park until the radiator cooling fans kick in just to see if the car starts to get in the overly hot zone? Does the recovery tank start to bubble or fill/overflow? Have you pressure tested the cap to make sure the cap is doing its job?

-Rod