Diagnosing Overheating Issues

[greg]

Hi All,

I've got a bit of a problem with my car running hot at the moment and was hoping someone may be able to give me some techie info on what the cause may be.

Basically, the car is running hot - this is mainly evident when driving along the freeway in 5th gear for extended periods of time (between 10minutes and 30minutes).

However, strangely, when driving through traffic etc the car does not overheat.

Details of the cooling system are as follows:
1. It has a thermo fan which is controlled by the car computer.
2. It has a fan shroud etc.
3. There are no inner guards in the engine bay (so air flow should not be an issue around the engine).
4. There is an intercooler infront of half of the radiator.

Other observations:
1. I'm not sure - but i think that the thermo does not run when we are travelling at highway speeds (even though this is when the car is running hot).
2. The thermo will definately run when the car is turned off and just sitting on accessories (if the temp gauge is reading more than 30%) and will then switch off (once the temp gauge is back down to 20%).
3. The thermo will also run when we are parked and the car is at more that 30% hot.

So my suspision is that it is something to do with the thermostat that runs the fan. But how can i confirm that this is the problem.

Thanks in advance.

[RaginRover]

start the car and then disconnect the thermo fan's sensor that goes to the engine temp probe, the fan should come on stratight away.

If it doesn't hot wire the thermo so it starts when the engine is on

Go driving on the freeway and try to make it run hot, if it doesn't
then the sensor is your problem, replace it.

Tom

[greg]

Thanks mate, sounds like a plan

Cheers

[greg]

Silly Question:

Would this sensor be affected by the temperature in the engine bay (rather than just the temp in the engine) - i.e. perhaps the air flow through the engine bay (due to no inner guards) means that the sensor stays cool when the car is moving at speeds, even though the engine is running hot.

[grimbo]

It shouldn't as I think most sensors are located within the cooling system and thus shouldn't be affected by the outside air temp. Or I could be wrong.

i had issues with my thermo fan for awhile and i fixed by replacing the sensor thing where the wires go into (don't you just love techno babble)

[manitou]

The thermo fan wouldn't be much use at freeway speeds as there would be more air going through the radiator than the fan could pull through wouldn't there?

I would start looking at the radiator because if it isn't a problem in day to day stuff

[greg]

The thermo fan wouldn't be much use at freeway speeds as there would be more air going through the radiator than the fan could pull through wouldn't there?

I would start looking at the radiator because if it isn't a problem in day to day stuff

But if the car starts getting hot - surely the fan would start running in an attempt to cool it down right?

[RaginRover]

I would start looking at the radiator because if it isn't a problem in day to day stuff

Depends,
the first trouble shooting exercise is the easiest, most overheating on highways is due to not enough fan power/no shroud etc etc. Stick with the simpliest things to try first before you run out and get a new radiator.

Tom

[murcod]

Perhaps wiring a light globe in parallel with the thermofan and having that sitting inside the cabin would be a good start? That way you'll know when the fan is coming on- being controlled by the ECU anything could be happening.....

[RaginRover]

Perhaps wiring a light globe in parallel with the thermofan and having that sitting inside the cabin would be a good start? That way you'll know when the fan is coming on- being controlled by the ECU anything could be happening.....

Good thinking I like that idea !

Tom

[Ruggers]

have you got an oil cooler on your car i have turbo on my cruiser and athigh speeds it gets hotter but in traffic it stays cooler this is becuase your running mre boost at a constant rate so it heats up its goes straight down when i get of the gas for a 1 minute. and the other thing to check is there isnt mud in your radiator or intercooler as this has the same effect of over heating on the high way and staying cool in traffic

[greg]

have you got an oil cooler on your car i have turbo on my cruiser and athigh speeds it gets hotter but in traffic it stays cooler this is becuase your running mre boost at a constant rate so it heats up its goes straight down when i get of the gas for a 1 minute. and the other thing to check is there isnt mud in your radiator or intercooler as this has the same effect of over heating on the high way and staying cool in traffic

I'm not aware of an oil cooler on it - unless the engine has one as stock...

I understand about the mud in the radiator - but once it gets that way - the fan should be running shouldnt it?

I'll do the first part of the diagnosis tonight and let you all know how i go.

Thanks

[Ruggers]

if its a toyota some have the oil cooler in the block near teh oil filter but these still arnt effeint ehough to cool them. i have an oil cooler form a rx7 waiting for me to get some fittings and fit to it. but have been told from a few guys that had the same problem fitting a bigger radiator never fixed it but an oil cooler did

[greg]

Thanks Ruggers - i've just re-read your previous post regarding boosting for a long time - and it could well make sense...

I've got a 2 stage boost controller - (with high and low settings at 15 and 9psi respectively)... However, in recent times i have seen that the low setting has crept up to more like 11 or 12psi... Perhaps this is due to leeks in the system? Or someone has touched the boost controller settings

Either way - i think i'll try lowering them back down to 9 again and see if that helps it stay cool.

btw - it's a suzuki capuccino engine - i'll check the factory service manual tonight to see about the oil cooler.

thanks again.

[Area54]

Whats the fuel economy like? Not too familiar with the little cappo motor, but how is the fuel/timing map? It's not leaning out at highway speeds? Timing advance problem? Is your efi compensating for the additional boost?

[paultherocksta96]

Pull the radiator out and get the core cleaned out. This will fix the getting hot while highway driving. Trust me this will fix the problem.

[greg]

have you got an oil cooler on your car

I checked out the FSM - there is an oil cooler on the engine just above the oil filter.

[greg]

Whats the fuel economy like? Not too familiar with the little cappo motor, but how is the fuel/timing map? It's not leaning out at highway speeds? Timing advance problem? Is your efi compensating for the additional boost?

Fuel ecconomy is the same as the 1.3 sierra was - basically about 10kms per Litre (depending on how much of that was in low range though).

I have just had a new timing belt installed - so i think the timing should be right (it was overheating prior to this though and still is).

I don't think that it is running too lean - the CPU is happy to run up to 1.1bar (15.1psi approx) before it will start protecting the engine on your behalf. This overheating is occurring when running between 9 and 12psi - so i think we are okay in this department.

[RaginRover]

Pull the radiator out and get the core cleaned out. This will fix the getting hot while highway driving. Trust me this will fix the problem.

MMMMMkay ........

"Go and throw money at it before we spend a few hours diagnosing the problem"

[Bazz107]

Am Having the same Problem with my Turbo Diesel 4Runner, is fine around town and the city, as soon as you push it up the Highway at 100 it starts heating up, Have had the Ratiator recored, removed the thermo, and replaced all hoses. have not been able to work it out. If anyone has any ideas would also be greatly appreciated.

[Damo]

Check your oil, it might be low.

[greg]

Check your oil, it might be low.

I've checked that - it's very close to full.

Coolant levels are also maintained up to the full mark on the overflow bottle (though this rarely needs topping up).

[carts]

I have an HJ60 with aftermarket turbo. Up the highway it runs hotter than when it was non-turbo, but around town it runs cooler than before. The radiator is clean and have also fitted a new thermostat. I have put it down to the fact that at 110km/h, the car is always running at high boost until you coast down hills, at which it cools right off. Bring the speed back to 90 and it runs cool again. I'm not worrying cause it never gets up to the red or boils over, nor does it use coolant.

[Area54]

Different kettle of fish with the diesel though as the fuel ratio is upped to make more power, more fuel also means more heat. Petrols will run hotter with leaner mixtures, hence the theory of mismatched fuel delivery to the boost.

Greg, has it always run like this since the conversion or just something that has popped up in the last few months? It is summer too...have you plumbed in an EGT guage to monitor rectal temps? You mentioned the boost has gone up lately, there are no restrictions in the intake after the turbo?

[greg]

Greg, has it always run like this since the conversion or just something that has popped up in the last few months? It is summer too...have you plumbed in an EGT guage to monitor rectal temps? You mentioned the boost has gone up lately, there are no restrictions in the intake after the turbo?

No it started off after the conversion without any overheating issues. A few things have changed since it was first installed.
1. It has now become summer - so this would make it more of an issue
2. It has been driven offroad - so the radiator does have some degree of dirt in it.
3. A front bar has been added - which does block off a bit more air flow to the radiator.
4. The boost has gone from 9psi to more like 12psi...

EGT? Exit Gas Temp? I presume this is the gauge that sits on the exhaust? No - haven't got one of these.

I'm not aware of any restrictions in the intake system.

I'm planning on testing out the fan with a test light, and also adjusting the boost back down to 9psi to see if together i can work out the problem. It is definately running high boost for extended periods when the overheating is occuring - so this could well be part of it.

[murcod]

EGT is exhaust gas temperature- and the guages aren't cheap to buy, so leave that as a last resort.

It would be a good idea to get your mixtures checked out with an air fuel ratio meter, particularly if you want to turn the boost up. It's never a good idea to assume the EFI is supplying enough fuel with increased boost.

Are you sure 9PSI is the standard boost pressure too?

[greg]

I think they are also called Pyrometers - the AutoMeter ones are about 700 bucks - so yes - that would be a last resort.

I'll double check the 9psi theory stock boost level - but yes - pretty sure.

[Area54]

EGT is very important with any turbo, it is virtually instant feedback on the load on the motor, engine coolant temp is a much slower and ineffective to gauge small changes in the combustion temperatures - water jacket conduction inefficiences with scale etc, flow restrictions, and where is the sensor? in the head at the front of the motor out in the thermostat housing, as far away as possible from no. 4.

I still reckon it's an internal problem, the highway speeds would rule out airflow, the motor is working its hardest at highway speeds, and what are the contributing factors with highway speeds? More fuel and high boost.

[paultherocksta96]

Pull the radiator out and get the core cleaned out. This will fix the getting hot while highway driving. Trust me this will fix the problem.

MMMMMkay ........

"Go and throw money at it before we spend a few hours diagnosing the problem"

Reading all this tech dribble isn't going to fix it but a $50 core flush might and it wouldn't do any harm anyway Otherwise check the cat converter if its old and the engines new it might be a bit blocked or to small for the hair dryer.

[paultherocksta96]

Am Having the same Problem with my Turbo Diesel 4Runner, is fine around town and the city, as soon as you push it up the Highway at 100 it starts heating up, Have had the Ratiator recored, removed the thermo, and replaced all hoses. have not been able to work it out. If anyone has any ideas would also be greatly appreciated.

Diesels are very different alltogether. Get under the car and give the main muffler a bang if it sounds a dull it might be clogged not such a problem around town but it shows on the highway. If it once wasn't a turbo but know is u also need to put a bigger can on it to prevent it getting to hot on the highway.