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The mkiv Supra Owners Club

Any ideas guys ?


Dnk

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Ok ive changed the heater matrix and a new radiator inc cap, also a new thermostat but now have another problem, all this was done a while ago.

 

The problem ive got is, as you raise the fan speed the temp coming out the vents drops to luke warm, no apparent air locks or gurgleing noises in dash.

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The heater matrix could be full of gunk - if you don't mind trying to sort out the inevitable air locks you'll introduce, disconnect the pair of hoses at the back of the engine that dissapear through the firewall near the passenger side, and stick a hose pipe onto one of them. :)

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The problem ive got is, as you raise the fan speed the temp coming out the vents drops to luke warm, no apparent air locks or gurgleing noises in dash.

Wouldn't you normally expect the temp to drop as you increase the fan speed, the air passing through the matrix obviously won't have as much time to warm up as it does at a low fan speed.

 

To what extent is normal I'm not sure as most of the time I have the fan speed low.

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The heater matrix could be full of gunk - if you don't mind trying to sort out the inevitable air locks you'll introduce, disconnect the pair of hoses at the back of the engine that dissapear through the firewall near the passenger side, and stick a hose pipe onto one of them. :)

 

We did all that Steve, flushed the system through before and after fitting the new parts, its been bled, bled, and bled again :(

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Wouldn't you normally expect the temp to drop as you increase the fan speed, the air passing through the matrix obviously won't have as much time to warm up as it does at a low fan speed.

 

To what extent is normal I'm not sure as most of the time I have the fan speed low.

 

Yes i'd agree with you, as you raise the fan speed the temp would drop but it used to be very very hot on full heat and full fan speed but now its nothing like it was :(

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Have you checked the condition of the rad?

 

It's new as mentioned in my 1st post :search:

 

Brand new rad, heater matrix, rad cap and thermostat all from Toyota.

 

Completely flushed through system and all fitted by very competant mechanic's who have done lots of work on my car for several years now so now its not down to poor workmanship etc.

Edited by Dnk (see edit history)
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It's new as mentioned in my 1st post :search:

 

Brand new rad, heater matrix, rad cap and thermostat all from Toyota.

 

Ah sorry mate that will teach me to skim-read.

 

Is the water pump in good nick? I've got a brand new Toyota one in the box in my garage and I'll do you a good deal if you need it.

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Mine turned out to be a disintegrating water pump, perhaps worth getting your waterflow checked?

 

I'll look into that but the car has never overheated or had any other problems related to the coolant system apart from the heater matrix leaking.

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Ah sorry mate that will teach me to skim-read.

 

Is the water pump in good nick? I've got a brand new Toyota one in the box in my garage and I'll do you a good deal if you need it.

 

No worries mate :)

 

I've got in my parts department a brand new water pump, oil pump, brake lines, full engine gasket kit, etc etc lol

thanks for the offer though Gaz :)

 

Think i'll fit the new water pump but have my doubts its that causing the problem.

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No worries mate :)

 

I've got in my parts department a brand new water pump, oil pump, brake lines, full engine gasket kit, etc etc lol

thanks for the offer though Gaz :)

 

Think i'll fit the new water pump but have my doubts its that causing the problem.

 

Furry muff mate, good luck with it. I've been there with the whole coolant system thing. Replaced the entire thing on my car.

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Air lock?

 

I fitted a bleed valve in the top hose that runs across the back of the head but that didnt make any differance, not sure what i check now other than the fun of taking the dash out but cant see it being the matrix blocked as we had such a good flow of water through the system.

 

The old rad that came out wasnt gunged up either but had just failed, wasnt rusty inside or any nasty stuff, the thermostat that came out was also fine and working, just changed for peace of mind.

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Check the temperature of the two hoses that go into the bulkhead. Get the car warm and use a basic multimeter temperature probe on the outside of the hose as a quick check. If the temps are the same then coolant is flowing to and back from the heater matrix. If the return hose (don't ask me which one that is) is cooler then you might have a flow restriction in the system after the work you did - kinked hose, screwdriver left in the pipework, that sort of thing ;)

 

-Ian

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Is the diverter flap for the main vents opening fully in the dash? Although I guess the air pressure coming out of the vents wouldn't change, whichever speed setting the fan was on...

 

Can that be checked with the dash in ? all the differant settings seem to work, footwell, screen etc

 

The fan blows through the vents no problem just the temp drops way more than i noticed before.

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Check the temperature of the two hoses that go into the bulkhead. Get the car warm and use a basic multimeter temperature probe on the outside of the hose as a quick check. If the temps are the same then coolant is flowing to and back from the heater matrix. If the return hose (don't ask me which one that is) is cooler then you might have a flow restriction in the system after the work you did - kinked hose, screwdriver left in the pipework, that sort of thing ;)

 

-Ian

 

Not checked them with a temp gauge but both inlet and outlet seem equally as hot, cant see there being a screwdriver in there but i'll get it checked ;) no kinked pipes that i can see either.

No gurgleing noises in dash, always runs bang in the middle of the temp gauge.

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Can that be checked with the dash in ? all the differant settings seem to work, footwell, screen etc

 

If you remove the upper glove box it is possible to see the linkages driven by the Air mix servo-motor, but you need to know what you are looking at. The linkages operates the diverter flap and the water valve.

 

You have exactly the same symptoms as I do and I have had a couple of attempts at fixing this, without success.

My next plan is to try to measure the flow in the hoses with and without the heater matrix. If I find a solution I'll let you know.

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Subscribed. I've also got these symptoms. I've recently changed my thermostat and bled the coolant system. My heater is luke-warm at best. I've checked the mechanical flap behind the glovebox, and that seems fine. The cause in my case could be an old heater matrix though, because I haven't changed that.

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