fan troubleshooting/ thermostat question

[BananaClip]

My car has a severe overheating problem. the fans only come on when I have AC or heater on, and don't stay on when i turn the car off. this leads me to believe it is the thermo-fan switch at fault, correct? do I need to run more tests?

How do I know which temperature rating my switch has? To the best of my knowledge the thermostat and switch are stock.

there is a small crack in the coolant overflow tank that opened up today (i had patched it before. the crack is pretty small and on the top of the tank- i don't think it's actually letting water out, just steam) and now the car gets hot enough to turn on the main alert on the instrument panel within 10 minutes of driving 55 with little to no traffic, WITH the fans forced on (slow setting, of course). This happened after I topped the tank off and let it cool to the first tick on the thermostat gauge. This is really alarming since before the crack opened back up I could drive in average to heavy traffic for half an hour or more and barely even need to force the fans on to keep it cool.

Thoughts? I'm hoping once the new coolant tank and thermo-fan switch go in (ordering them tomorrow) everything should be good.

I've already screwed this car up like this once and I am NOT going to do it again, so the car isn't going to move until I have this figured out. It did start knocking under throttle right before I got home, but I didn't get any loss of power or smoke or other bad sounds .

Thanks yall!

[bearone2]

when you replace the switch and tank it should be fine.

[HondaDustR]

The overflow tank on these cars is not like classic overflow tanks. It is pressurised along with the rest of the cooling system, and will most likely cause a lot of problems if it leaks. It should work fine once you get those parts installed, along with some fresh coolant. Just be sure to bleed the cooling system well, since the thermoswitch will often not activate if there is a lot of air in the system.

[bud9344]

That is not the overflow tank that is part off the radiator system. By repalcing the tank and make sure there isno air in the system it might just do it. When you refill the coolant in the car make sure you crack open the bleeder bolt (Size 12mm wrench) to let the air out off the system.
Recently purchase an 87 944S has no water in the tank and has a crack on top Drove the car for about 2 mile the temp needle almost to the top. I replace the bottle, happen to have in the garage from the totalled car which doesn't fit the 951 and also found another leak on the water pump housing which has the plastic cover in it the O ring dried out and it was leaking and also found another leak on the heater hose close to the water pump the hose dried out.
It is good to go now the temp reading is normal

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87 930 black (52000 mile on it) Show car
87 944S White Son daily driver
86 951 Black on Black daily driver
83 944 Auto wife's car
83 933 Black bought it back from dead

[BananaClip]

bump because it is STILL running hot. it just gets hotter and hotter until it turns on the emergency light, and then when i park the fans stay on for about a minute or less. it is no longer leaking, at least.

what is the best way to vent the system?

will it matter if I don't have coolant in there, just water?

the car has a mystery thermostat in it, I also just found out. the thermo switch is the original 83/ 102, but it is a brand new one. if the thermostat is a lower temperature will it cause fan behaviour like this?

[zedsn]

Hi, normally when a fan switch breaks the fans will stay on all the time so you might want to look for a problem somewhere else. You could temperarily hook up your fans from the battery to a switch and see if having them come on when they are supposed to will keep your car cool. Water isn't the best but it will do for now till you get your cooling problem straitened out. You bleed the system by loosening a bleeder bolt on top of the engine where the upper radiator hose goes. Maybe your thermostat isn't opening all the way too that could be compounding the problem but I would look at getting the coolings fans to come on line and go from there.

[fbgh2o]

Check the resistors in the passenger footwell. The wiring often gets fried and prevents the high speed fans from coming. Also, check the relay,it may not be operating correctly. I had one which would only let the low speed fan come on and nothing else.

[BananaClip]

would it run the fans on low after you parked in lieu of high? i think they are still on high after I stop. I'm going to bleed the coolant in the morning. what resistors in the passenger footwell should I look for?

Thanks.

[BananaClip]

yesterday I bled it, put in stop leak for a leak that I still couldn't find, and put in coolant. it stayed cool for longer than usual but still overheated and the fans stayed on high for about a minute after i turned it off (though the temperature was still way in the red when I checked after the fans cut off). i checked it again this morning and lo and behold the expansion tank was empty. i realize now that I didn't bleed it properly since I didn't know you had to have the engine running while you bled it. could it be that trapped air bubbles are overpressurizing the system and forcing coolant out the overflow on the tank? I'm running out of ideas and things to fix

[Slam]

Is the cooling system getting over-pressurized? What you're describing could be a bad head gasket - I know this because my car behaved exactly as yours is now. I replaced the radiator and that helped a great deal but things didn't return to normal until I did the HG. Of course, these systems are completely intolerant of air in them. I'd bleed it every morning until I was sure the air was out. You can also give the car mouth-to-mouth by blowing into the header tank with the bleeder off. Just be careful. YMMV!

[BananaClip]

i already blew the headgasket earlier this year, and just got it back less than a month ago. it ran fine for a while. there's no coolant in the oil nor oil in the coolant as far as i can tell.

it did overheat kinda bad earlier but it runs the same as before. since the head gasket replacement it doesn't idle well when cold and takes a little more effort than before to start, but i'm thinking that's either electronics or vacuum.

[mikepellegrini]

The cooling system is designed to run at about 10-12 PSI. If you have steam escaping from the expansion tank, that would cause the system to overheat.

Stop leak products are not a great idea generally because they'll often plug up things that should not be plugged (like radiator and heater passages and what not). While they may seal some small leaks, at least in my opinion, they cause more problems than they're worth. I wouldn't use that stuff in any car I cared about (but by the same token, it worked great in an 87 Taurus Wagon I had ).

Coolant works better than water at engine cooling - a lot better - because it has a higher boiling point, among other things. Water is way less efficient.

Thermofan switches are cheap and easy to diagnose and/or replace. Here's the procedure at Clarks: http://www.clarks-garage.com/shop-manual/cool-01.htm

When you bleed the cooling system, it helps if you have the car raised in front (look where the bleed screw is - at the front of the engine - you want that to be the highest point). You also oughta have the heater full on - hot (the heat control, not the fan).

When you park the car, the driver's side fan will run on low until the temp in the radiator falls below the cut-off (which depends on what temp thermofan switch you have).

There are about 3-4 different temperature ranges of thermofan switches available - from low temps to high-normal.

[HondaDustR]

Originally Posted by mikepellegrini

I wouldn't use that stuff in any car I cared about (but by the same token, it worked great in an 87 Taurus Wagon I had ).

Coolant works better than water at engine cooling - a lot better - because it has a higher boiling point, among other things. Water is way less efficient.

.

Haha! emphasis on "any car I cared about"!

Water is actually better at cooling than glycol, but is not practical for street driving, since it freezes and boils too easily. The first bit of traffic you get stuck in and you're screwed.
As long as you keep moving so the coolant never gets a chance to heat up higher than the thermostat specification, then it should be fine. I've heard many racing leagues actually mandate the use of water as a coolant, so if someone's car takes a dump, it won't make the track slippery.

[BananaClip]

I filled it up and bled it completely yesterday and it drove for about half an hour before overheating so i'm ~90% sure it's just a radiator leak holding this car back. i'm going to go ahead and do the stop leak again because I think I screwed it up last time and I really just need it to run so I can get moved out of my current apartment since the lease is up saturday. Next week or two i'll probably go ahead and replace the radiator since i'll have a driveway and all my tools back-- i just can't address this problem properly right now. i just want the silly thing to drive me 45 minutes away and then back.

to clarify, i replaced the thermo-fan switch a few days ago and the fans come on and lower the temperature properly-- as long as there is coolant in the system!

Originally Posted by HondaDustR

As long as you keep moving so the coolant never gets a chance to heat up higher than the thermostat specification, then it should be fine.

e: so once the coolant gets over 102 C it is going to overheat no matter what? i suppose it's a bad idea to use straight water with a 102 C thermostat too since it has to boil before activating the second fan setting. hadn't thought of that.

[BananaClip]

ok, now the car is only losing coolant (still just water) through the overflow tube from the tank. every time I stop it is dripping. over 10 miles of city driving yesterday I lost half a gallon. if I put my last gallon of antifreeze in it will it all blow out the overflow too? keep in mind it is getting close to 100 outside every day!

[Slam]

Who did the HG replacement? I'd go back to him/her/them with this problem.