Overheating

[telsun]

My 98 2.0 Avensis started overheating today whilst we was in a traffic jam. I turned the heater full on which dropped the temp down and got home fine.

When I got home I left the car ticking over on the drive until the temperature got to just below the red. I think that it's doing this because the fans aren't kicking in, I presume they should kick in before then.

What should I check for? I'm hoping that it may just be a relay or something....

[Stephen Kowalzcuk]

My 98 2.0 Avensis started overheating today whilst we was in a traffic jam. I turned the heater full on which dropped the temp down and got home fine.

When I got home I left the car ticking over on the drive until the temperature got to just below the red. I think that it's doing this because the fans aren't kicking in, I presume they should kick in before then.

What should I check for? I'm hoping that it may just be a relay or something....

First thoughts are the thermostat is faulty, secondly water pump problem, internal leak perhaps or impeller damaged or worn, but you say coolant level is ok so I would look at testing and probably replacing the thermostat or coolant temp sensor, its not a big hassle.

[gazza1286]

The test is quite simple.

Run the car from cold (stationary with bonnet open). The upper hose to the radiator will warm up within 3-5minutes. The lower hose on the radiator which returns to the engine will remain cold.

Keep an eye on the temp guage. Shortly after the needle reaches the 'normal' reading The lower hose will begin to warm up. This will take about 10 minues (or even more - be patient)

If the temp needle continues to rise and the lower hose remains cool/cold you probably have a fault with your thermostat. (i.e. it needs replacing).

The fan will normally kick in when the lower hose gets to a similar (but lower temp) to the upper hose. The fan is a purely secondary method of cooling. If the thermostat is faulty the fan cannot (by itself) cool the engine sufficiently.

Your coolant should rise (into the expansion tank) when your your car gets hot. If not, there is POSSIBLY a problem with your radiator cap. (unlikely). If there is a fault with it you will see the lower hose being squeezed flat due to vacuum pressure when the car is cold.

The O/S fan is primarily designed for the A/C. It will kick it but only as the main fan starts and is unable to cool the engine itself. (unless the main fan has a fault).

[silverarrow]

thermo switch in rad gone common fault

[telsun]

Thanks guys. Any idea how much a thermo switch is? I'm going to a breakers yard tomorrow is it worth getting a s/h one? Where exactly is it fitted? Is it a 5 minute job, what's involved?

[gazza1286]

The 'water temperature sender' is easy to find.

Follow the lower radiator hose back to the engine. The casting to which this hose is connected will have various other hoses and bits attached to it. The sender is the only item which has electrical wires coming from it. You will clearly see that it can be unbolted.

Do not assume this is faulty until you have carried out the 'thermostat test' I described above. As stated the fan (of itself) cannot keep the engine cool if there is a fault with the thermostat.

If the fan isn't working there could be other reasons. The fan motor may have packed up or the wiring may be faulty.

By the way if you turn the ignition on (engine not running) and disconnect the plug to the sender. the fan should operate immediately.

Good luck

[telsun]

Thanks Gazza. I done the thermostat test and the lower hose does indeed get hot so I can rule out a faulty thermostat.

I may be a bit of a dunce but I can't see anything electrical coming from the housing that the lower hose connects too....

[telsun]

Ah no hold on I think I have it. It's on the right hand side of the engine bay about the height of the cylinder head right?

I just rung Toyota and they told me its £33.03 + vat

[telsun]

This it?

http://webzoom.freewebs.com/kojima/Picture.jpg

[telsun]

By the way if you turn the ignition on (engine not running) and disconnect the plug to the sender. the fan should operate immediately.

If I have got the right part, as in the pic, then this test did not work! So perhaps it's a electrical fault....

My air con doesn't appear to be working either, the light doesn't come on when I push the button and the fan doesn't kick in (should it?)

[gazza1286]

I have a 1.8SE (2000) with a 7A-FE engine. (slightly diferent to yours but the principle is the same) Your picture is different to my car but that shot could only be the temperature sender switch.

There are a couple of things here:

IF your fan motor is OK (and the wiring) IT WILL come on when the engine is cool and the sender connector is removed. (at least it does on the 7A-FE). The Air-con fan will ALSO come on at the same time as you run this test.

IF the sender is faulty it will not send a signal (during normal operation) to the fan SO the fan wont come on when the engine hits (or just exceeds) normal operating temperature. Again the Air Con fan will also come on at this point.

Your air-con fan ALSO should come one if you are using your air-con (perhaps a relay/fuse is causing a problem with your air con). It still should come on as described above.

You may have a fault with the Fan! There is a connector on the wiring harness clipped to the fan housing. If you disconnect this and provide a direct feed from the Battery using a couple of wires and spayed connectors the fan shoud start. If not its a trip to the breakers yard. (you can't buy internal parts for these from Toyota and the fan motor cost about £125!!)

You can run a similar check on the air-con motor but I think the reason why this one isn't running is because the air con must have tripped out /blown a fuse when the car over heated.

Question:- when you ran the thermostat test did the temp gauge continue to rise into the red?

If this test went as expected you must be getting some coolant circulation. BUT is the drive belt on the water pump slipping??

This is the one which will run both the power steering pump and water pump from the bottom pulley.

[gazza1286]

Checked my Carina Handbook. Will probably be the same for the Avensis.

On the 2.0 (3S-FE) the Engine temp sensor is on the Housing (I think your photo is of that)

The Cooling fan temp switch on the 2.0 is on the radiator (as per telsun).

So many different models!!

Can't wait for the Haynes manual due in the Summer!!!!

[telsun]

The Cooling fan temp switch on the 2.0 is on the radiator

Do you mean as per Silver Arrow? Is there a way to test this? I think I saw it earlier is it on the nearside at the bottom and then find its way up toward the headlight and back behind the rad (!)?

When I done the thermostat test I didn't allow it to run long enough to get up to the red, but yesterday when I ran it to see if the fan was kicking it I did. I didn't notice any slipping of the belt.

[gazza1286]

Yes, Silver Arrow lol!!

I presume that the fan hasn't come on at any time then? It is looking like the cooling fan temp switch is the problem.

I'd do a direct feed to the fan as well - just to be sure (I've just had to replace my fan as the internal brush holder had collapsed).

The reason why I'm sceptical about the fan not coming being the entire problem is that I've been driving for 2-3 weeks knowing that I'd had a broken fan and the temp needle has never gone above the centre reading.

How long did you drive before it began to overheat?

I'm a bit reluctant to suggest a test (given that I've been trying to give you duff info all day HaHa) But disconnecting it may let the fan run in the 'cold' setting as in my engine. However the main problem is the fan not cutting in when it should. Of course doing the 'cold' test would do two things - it would prove the fans work and confirm that there isn't a fault with the wiring.

Keep us posted!!

[selfbuild]

Find the fan temp switch on the radiator (this is the one that controls the fan), disconnect it and using a piece of wire, put it in the the connetor across the two pins (not the temp switch on the rad). Now turn the ignition on and the fan should start up.

If the fan does start up then the switch in the rad is faulty. If it doesn't start up then the fan is faulty.

[telsun]

Can you give me a clue as to where to find the fan temp switch on the radiator?

[gazza1286]

The only picture that I can see isn't particularly clear On the bottom piece of the radiator (lower than the fins) you will see a two wire electrical cable attached to a push connector which is secured to a hexagonal bolt on the inner face. It will be the only electrical fitting on the radiator itself.

Its probably hidden by the fan housings.

[telsun]

Thanks Gazza I did have a look, I figured it was pretty much where you said, looking on the forum there seems to be a pattern of the sensor being near the drain valve. Anyhow I'll have a look tomorrow in the daylight, think I might collar me dad to give us a hand too :)

I'll keep you informed....

[telsun]

The saga continues....

Me and me dad had a look today, unfortunately we didn't have the means to connect a direct feed to the fan or have a volt meter to test it.

We pulled the Thermo switch which didn't start the fan but did bring up an engine management light on the dash and drop the temp gauge. So we assumed that was working correctly (?)

Next port of call was the fan temp switch, but we couldn't find the little burger anywhere!! WHERE IS IT??? I still have my Carina which is the same engine and a physically identical radiator, where the fan temp switch is located on that radiator there is a bung in the Avy. What we did find out is that when we pulled the fan temp switch in the Carina the fan came on. So we assume the same will happen on the Avy....if we could find it!

[telsun]

I still need to sort this out has anybody currently on the forum got any ideas/ advice?

[Penfold]

telsun,

there was a mention earlier in the thread of checking fuses. were they, and the relays, all OK?

there are 2 fuse boxes by the way. the big black box of fuses on the LHS of the engine bay and the smaller one inside the dash by the drivers right knee.

is the fan belt correctly tensioned so that the water pump is shifting the coolant effectively ?

[telsun]

Thanks I'll check all my fuses at the weekend (and no I didn'r know that there are two lots!) how can I check that the relays work ok?

[Penfold]

Thanks I'll check all my fuses at the weekend (and no I didn'r know that there are two lots!) how can I check that the relays work ok?

The relays have a part code on them. pick one with the same code but working a known good system and swap them over. if the fault shifts and the fans come back to life then it'll be the relay.

The alternative is to use a test meter but that's beyond my competence so if there are any sparkies out there who can help now's the time to wade in.

good luck

[telsun]

This is my last remaining problem with the Avy can anyone else shed any light?

[jed50]

This is my last remaining problem with the Avy can anyone else shed any light?

Hi telsun, I maybe going over old ground here and I may sound a but stupid, but your radiator isnt blocked is it? With all these gadgets on modern cars these days its hard to diagnose any problem. Years ago I had a mk5 cortina that used to overheat in traffic but was ok on a long run. Water pump, thermostat, rad cap and head gasket all ok. (No electric fans in those days) Found out that the radiator was partially blocked. Might be worth a look! By the way if I am being stupid please tell me! Jed.