Help Fault Isolate 93 Corolla Overheat Problem

If the gauge is past it's normal point, they should be on for sure. At normal temp, they may be intermittant, but that won't last for long, if they aren't working. Checking the flow probably wouldn't be a bad idea, but I kinda doubt that is the problem if the pump is not leaking. Yes, they often leak when they go out. And often the bearings start to seize and it will scream like a scalded house cat. Usually, on the JA car water pumps I've seen, they go real quick.. Once one starts squealing, or leaking, you better park it, as it's soon oclock.. I had one flake on me while I was working on the car. One minute it's ok, the next, it starts gushing water, and screaming.. I ended up adding a timing belt, pump, and seals to that adventure.. Sounds like your fans are out, or the radiator is clogged and shot.. Probably fans if this came on suddenly. You would want to test for voltage at the fan motor leads. If voltage, the fan is bad. If no voltage, the relay or wiring is bad. MK

On Jun 16, 7:57 pm, snipped-for-privacy@wt.net wrote: If voltage, the fan is bad. If no

BTW, there is also a fan thermostat too I think... MK

I am assuming that your car has the same motor to the ones in Oz, and I'll work from that.

In the motor it is different to every other motor in that the thermostat lets cold water in and not hot water out so the top radiator hose will get hot no matter what. it also means that if you check for water flow by removing the radiator cap all you will do is pump the water out until it is below the water pump (however you will know if the pump is working).

The first thing I would do is replace the thermostat, or if you cant get one right away and you need the car cut the middle out of it. It is most likely the cause of the overheating and is also the cheapest to replace. If you cut the middle out all that will happen is that the car will pump water all the time and take longer to warm up, maybe never if the radiator is working properly.

As for the fans, the should operate when the engine computer or a switch determines the engine water temp has gone to ~102oC. However is the thermostat is not letting water for correctly they will not do much to cool the engine.

Nick

Hi Nick and TNX for your information.

I am not even a home auto mechanic; don't have any (metric) tools.

I just checked for operation of those fans and also the lower radiator hose.

[1] The lower radiator hose is only a little warm when the dashpanel TEMP gauge is nearly at the "H" point, i.e., well above normal. [2] While well above normal engine coolant temperature, neither of the two fans began to operate. [3] Able to get plenty of hot air out of the passenger compartment heater vents.

I am assuming that the coolant theromstat is located at the top hose. If true, then I may attempt to replace that myself with use of an adjustable wrench.

Isn't it strange that the fans did not come on either ? I wonder where that fan thermostat is located on my 93 Corolla. And, if there is a separate fuse for the fan circuit.

Is it still true that a test of the coolant theromstat can be done by placing it into pot that is filled with water, and bring water temperature to 212F ?

What do you (guys) think?

de ~Vince~

Ok First things first. If the bottom hose is cool and the temp gauge is off scale then I would replace the thermostat as it lets cold water out of the radiator and back into the motor. If it was open both hoses should be the same temperature.

It will be in where the BOTTOM hose attaches to the motor and is probably jammed closed. This is different to nearly every other car made.

You can test it by putting in water then heating it up until it boils but it's best not to let it touch the bottom or the sides.

Have a look and see if you think you can change it. it should only be a matter of removing two or three bolts and the clamp off the radiator hose. There may also be a electrical plug attached to it as well. (If this is the case your fans are not working as the switch to turn them on is that electrical connection and the water is not getting hot enough.) You then take out the thermostat and put a new one in. spring side to the motor.

Also coolant will go everywhere so do it in a place where it can get wet, there is about 1.5 gallons of coolant in the whole system.

If you think you can do it. you will need the following things.

A new thermostat. A thermostat housing gasket. (depending on the design) Coolant/Antifreeze enough for 2 gallons. (you should not use it all but it's best to have extra) And a socket set if you can afford it. (cheap set should do as the bolts will not be super tight)

If you have any questions, you local auto parts store can get you the right parts.

IF you don't feel confidant, take it to a mechanic. I make to claims that I have explained it well enough.

The fans do have a separate fuse which will be in the engine bay somewhere. It should show you in the owners manual if you have it. if not it will be under a plastic cover somewhere most likely near the battery.

The bottom hose should be cooler than the top hose.

Does one of the fans come on when you turn on the air conditioner?

When engine coolant temp is high, at least 1 fan should come on. I suspect the either the fan or the coolant temp switch that controls it is bad so both should be checked.

I do not recommend using an adjustable wrench because you can strip the bolt heads. IIRC, the bolts are 12 mm. so you can invest in a 12 mm wrench and a gasket scraper for the job. If you remove the thermostat housing, you will need to use a new thermostat gasket when replacing the thermostat, and a gasket scraper makes cleaning up the old gasket easier if it does not come off cleanly. After you remove the housing, pay very close attention to the orientation of the spring on the thermostat and to the small hole with what looks like a slsiver of metal stuck in nthe hole, and replace the thermostat exactly the same way. If in doubt, take a digital picture.

The fan should come on. The coolant temp switch should be located near the thermostat housing, where the top hose goes to the engine. There should be a fuse or fusible link for the fan circuit.

Yes, but the thermostat should open somewhere between 160 and 190.

It is MUCH cooler. I could leave my hand there for seconds, whereas the top hose was so hot that I was unable to keep my hand in contact for more than an instant.

Yes; the fan located between the radiator and the engine block came on when the A/C was turned on.

Where might I find a schematic of the fans' electrical circuit? I wonder if I could remove a connector and place a jumper-short/resistance in place of the switch to trigger operation of the frontmost fan ?

I can see a device that is right at the elbow flange at the water pump. WOW! That is tight space for my fat hands to reach.

There are several fan fuse stencel markings visitble at the fuse compartment. They identified by numbers 1, 2, 3, etc.

I am thinking that I might have a better chance at testing the electrical circuit for the fan and control switch rather than trying to remove, test, and replace the coolant temp theromstat.

Regards. Vince

That's incorrect.

The thermostat is a valve that opens when the temperature of the coolant gets to a certain temp, like 175 F or 195 F. It lets the hot coolant out of the engine and into the radiator.

Jeff

You are wrong.

Toyota has the thermostat on the cooler water inlet to the engine.

If it is the fans causing the problem which I doubt if you can hold the bottom radiator hose the motor should cool down if you turn the air con on as the fan it turns on will suck air through the radiator.

If the problem is anything other than the thermostat I'd be very surprised. If you don't think you can do it, take it to a mechanic.

Well damn Toyota must have put their cars together wrong and I have seen at least 3 front wheel drive Toyota's all with different engines that have the thermostat in the bottom hose letting cold water in. I suppose that the gen-one Honda civics engines don't spin anticlockwise either.

You're right.

In most American vehicles, the thermostat is on the engine where the upper radiator hose connects. I believe this is true with most engines with thermostats.

In some or most Toyota cars, the thermostat is where the lower radiator hose connects to the engine. This seems rather weird to me. I think that by measuring the temperature of the coolant going out of the engine (which should be the hottest coolant), one would control the engine temperature more accurately.

I have also seen it suggested that the Toyota thermostat lets the engine warm up more quickly, but doesn't really control the engine temperature.

Jeff

I suspect that the thermostat is not opening and allowing coolant to flow through the radiator, unless your radiator is working VERY well!

Go to

- you have to register your model year, make, and model vehicle and you can get access to their on-line repair guides. They do not have guides for all vehicles, but they do for 1993 Corollas. I checked, and in the engine and engine overhaul section for your car, there is a guide for replacing the thermostat and in the cooling fan section, a guide for testing the fan and temperature sender and associated relays.

IMO, these guides are great for a do-it-yourselfer, with enough information to check and replace or repair components, without the detailed information that the average do-it-yourselfer would not attempt or understand.

Look at the guides and post again if you have questions about anything in them.

good luck!

That used to be the way TS were tested but I believe nowadys with TS in a high presure cooling systen it doesnt give you a true picture of the reliability of thee TS.

The TS MAY ? open ok in 1 atmosphere of pressure but with cooling systems routinely using 15-20PSI pressure caps it MAY NOT open under pressure.

If its the original TS its time for a change.

I am pretty sure that Toyota still uses the "traditional" method of testing thermostats in a pot and heating the pot.

98% of the cars I have seen have the thermostat letting hot water out even Toyota's but cars with the S and A series motors the thermostat lets in cold water. it is us usually designed that the sensing body is in the back of the water pump to measure the temp of the water being pumped back into the block.

The system is designed with a bypass the allows water to bypass the radiator and go back into the back of the pump which allows coolant to flow and stops pump cavitation. These two motors also have a high racing pedigree with the S Series being designed to have a turbo hanging off the side, and the A series a almost direct copy of the Cosworth BDA engine. These motors also tend to have a thermostat that opens around 10 degrees earlier then motors with normal thermostats.

The gauge on my dads Celica with a 3S-GE will move around by about two needle widths depending if it's city or highway driving he's doing, and it will move a full quarter of the gauge before the fans turn on. Having said that though the car has always done it and I think it is more to do with how the gauge is calibrated than anything else. My car has a model

6 years earlier where the gauge sits on half a normally and 3/4 when the fans turn on but mine sits on 1/4 normally and 3/8 when the fans turn on. Both motors are the same v6 with the same part number for the senders, only the gauges are different.

Nick