Wiring advice

[Marshmallowman]

You would have a thermstat that opens once your car warms up, by all indications this is ok as you don't have cold start problems and your car runs cool when moving.

So then its either the temp sensor for the relay that turns on your thermo fan is dodgy, or it is set to to high a temperature. Is this the factory sensor/switch or is the whole thing an aftermarket thing with some adjustabilty?.

Failing that your themo fan just does not pump enough air, so just leave you car idleing and see at what point your thermofan starts running . if it starts nice and earliy then its just not pumping enough air..and I take it you have it the right way arounnd.

[Jon P. Inghram]

It's worth a try to change the cooling system cap. I had a bad radiator cap on my car that caused all sorts of wierd cooling problems that I couldn't figure out until I replaced the cap. Turned out it wasn't made correctly and the inner seal didn't contact the seat inside the radiator, when the engine warmed up the cooling system wouldn't pressurize.

[spadnos]

You shouldn't just parallel the two fans as LvR suggested - this will likely start frying fuses, since both fans may be run off a single wire (and relay, which may also get carbon deposits on the contacts after many fan stops).

The "right" way to do is would be to somehow replace the single pole relays that are in there now with double pole relays, and use the extra pole to turn the oher relay on. (a double pole relay is like two switches instead of one - it makes contact on two separate pairs of wires at the same time) You may need another level of relays, depending on how they are controlled now.

I'd have to agree with all the others who have suggested fixing the problem rather than delaying a bigger one

- Steve

[Brian Ellis]

A few words on anti-freeze. There are all kinds of rubbish sold as anti-freeze and some good ones. NEVER use a cheap one, as it will be an expensive one. A good anti-freeze will be buffered. This means that the pH of the concentrate will be typically about 8.5 (never higher) and this will drop slightly to about 8.3 or 8.4 when diluted. The reason for the buffering is that ethylene glycol (MEG) slowly decomposes at engine temperatures, forming glycolic acid aka hydroxyacetic acid which is very corrosive. The buffering neutralises this while keeping a constant pH. A good product will also contain a corrosion inhibitor, so that different metals forming an electrochemical couple cause less corrosion. This is especially important if the cylinder block or the radiator itself is in aluminium. It will also contain a preservative for elastomers. The hose pipes are usually in a blend of natural and synthetic rubbers whose composition is designed to have minimum hardening because of flexibiliser leaching by the MEG solution. However, a raw MEG solution, which is quite an aggressive solvent for organic materials, would harden the pipes in about 2 years. A preservative will reduce this happening. It will also reduce the risk of an accidental spill attacking paintwork. A good one will also contain an algicide, to avoid the risk of a build up if the car is left stationary for a couple of months.

IOW, anti-freeze chemistry has become quite complex: it is not just a question of stopping the coolant from freezing but also preventing damage to the car's organs.
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BTW, one other cause of overheating at rest is a worn water pump: if it is not pumping sufficient coolant into the radiator with the engine turning at < 1 krpm, then the result is obvious. The rotor could have the vanes worn by cavitation, especially if you use the engine a lot at high rpm.

[Kooldino]

So then its either the temp sensor for the relay that turns on your thermo fan is dodgy, or it is set to to high a temperature. Is this the factory sensor/switch or is the whole thing an aftermarket thing with some adjustabilty?.

I think you guessed it right. I pulled off the radiator cap last night and cold started the car. I monitored temps, and it got to around 210* or so, and the fan did not kick on. The water in the radiator appeared to be moving.

I removed the quick connector for the fan and kind of hard wired it. Did the test again, and the fan kicked on at 207.

Also to note: If I turned the A/C on at idle, both the AC fan AND the radiator fan would be on, regardless of the temperature. I guess this makes my wiring a bit more tricky.

[Kooldino]

It's worth a try to change the cooling system cap.

It's been done. I went from a 1.1 bar cap to a 1.3 bar cap.

[degrub]

i think he meant "replace" rather than increase the pressure. Which hose do you want to blow first ?

[MultimediaMan]

I've read through this entire thread...

Raising the pressure of a cooling system is a valid way to increase cooling efficiency: if you are having problems with localized boiling or hotspots, the increased system pressure will inhibit boiling. Many people think cooling is a question of sheer volume of cooling air or volume of cooling water. Coolant should move as quickly as possible through the galleries in order to remove heat. 1.0 to 1.3 Bar is only like 5-6 PSI difference: not much mechanically speaking for an automobile, but it raises the boiling point of the coolant quite a bit.

Kooldino, you might have a Thermostat stuck OPEN causing problems.

Back in the day, we would see this on some sport bikes in Arizona: The bike would run poorly and seem to run very hot in stop and go traffic, but it was always full of coolant, and seemed to boil over all the time. The discovery was made when we did go into the cooling system and found the Thermostat removed. Simply replacing the thermostat restored normal operation.

It is a common practice in that state to run with the Thermostat removed on some older makes of cars (particularly muscle cars) because the thermostats were always a source of concern getting stuck shut, and when it never gets much below 70 degrees Fahrenheit, who needs one anyway? Guys making the jump to bikes used the same logic and remove the thermostat even though it is often used as a pump pressure regulator in addition to a flow regulator. (Pump flow pressure and Static Cooling pressure are two different things).

I do not know how the waterpump arrangement is on your car, but I'd take a hard look at that Thermostat.

[Kooldino]

i think he meant "replace" rather than increase the pressure. Which hose do you want to blow first ?

Well, I replaced it with a better one. It's a cap made by mazda for my radiator. It's designed to safely run my current cooling system.

[Kooldino]

I've read through this entire thread...

Raising the pressure of a cooling system is a valid way to increase cooling efficiency: if you are having problems with localized boiling or hotspots, the increased system pressure will inhibit boiling. Many people think cooling is a question of sheer volume of cooling air or volume of cooling water. Coolant should move as quickly as possible through the galleries in order to remove heat. 1.0 to 1.3 Bar is only like 5-6 PSI difference: not much mechanically speaking for an automobile, but it raises the boiling point of the coolant quite a bit.

Kooldino, you might have a Thermostat stuck OPEN causing problems.

Back in the day, we would see this on some sport bikes in Arizona: The bike would run poorly and seem to run very hot in stop and go traffic, but it was always full of coolant, and seemed to boil over all the time. The discovery was made when we did go into the cooling system and found the Thermostat removed. Simply replacing the thermostat restored normal operation.

It is a common practice in that state to run with the Thermostat removed on some older makes of cars (particularly muscle cars) because the thermostats were always a source of concern getting stuck shut, and when it never gets much below 70 degrees Fahrenheit, who needs one anyway? Guys making the jump to bikes used the same logic and remove the thermostat even though it is often used as a pump pressure regulator in addition to a flow regulator. (Pump flow pressure and Static Cooling pressure are two different things).

I do not know how the waterpump arrangement is on your car, but I'd take a hard look at that Thermostat.

Yeah, I heard bad things about running w/o a thermostat.

Hopefully my problem the other night was just due to the fan not kicking on.

I'm waiting on new brake rotors to come in, so I'll have to do more testing later.

That said, I may be changing my thermostat out for one that opens at a lower temp.

[degrub]

This is an intermittent problem right ?

CHeck the resistance of the coil on the fan relay, look for burned contacts on it as well. check the temp the fan is supposed to come on. IF it is more than 5 degrees off. replace the sensor.

You say you just replaced the cooling fluid ? did the overheating while stopped start after that ? or after a previous change ? you might have an air bubble in the top of the engine. Be sure you got the bleeding procedure exactly correct.

IF the thermostat is failing open, then you may not have enough pressure in the hottest part of the engine while at idle and you can have localized boiling. you can test it suspended by a thread in a large pot of water on the stove that you heat up slowly and check the temperature it starts to open and then goes fully open at.

i'll bet it's #1 or #3.