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heaters cold but all pipes are hot. and no over heating


NOODLE

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After buying my supra a couple weeks ago it was all good until it randomly started to blow cold air. when i tried bleeding the system i got hot air again, but once i drove the car about 2 or 3 miles it went cooler until it was cold again, i then changed the thermostat, jacked up the front of the car and bled it again and still no hot air.

 

i did notice when i changed the thermostat the flow of anti freeze wasnt very good, so i removed it just to get me home. the car doesnt seem to be over heating at all and the temp gauge stays at the running temp and has not gone over half way. i have a feeling the pipes running into the heater matrix have corroded and blocked the system but both pipes going into the bulk head are warm when up to temp. the pipes just feel brittle when u squeeze them has anyone had this issue? any help would be great thanks

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Check the mechanism for opening and closing the heater matrix valve hasn't came off. This can be seen underneath the glovebox on the passengerside IIRC, behind the dash. It's a rod that pulls and pushes the valve to open. It's quite common for this to detatch itself causing cold air.

 

That wouldn't explain why you had temporary heat though.

 

Is the air stone cold regardless of engine temp? Are the pipes leading to and from the bulkhead roasting hot? Ie both are very hot to the touch and after a run you would struggle to hold them? Generally when you have a blockage the "out" pipe is significantly cooler, barely luke warm.

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If you have to bleed the system then its losing coolant somewhere.

Is there any coolant in the expansion tank ? do you have

an expansion tank ? i checked a supra a little while ago and it had no tank, hence it kept needing to be topped up and bled !!

 

Is your passenger footwell damp, (leaking heater matrix)

Edited by Dnk (see edit history)
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If you have to bleed the system then its losing coolant somewhere.

Is there any coolant in the expansion tank ? do you have

an expansion tank ? i checked a supra a little while ago and it had no tank, hence it kept needing to be topped up and bled !!

 

Is your passenger footwell damp, (leaking heater matrix)

 

not losing water the expantion tank has water in it topped up to the max after changing the thermostat,

 

io did have to top it up when i brought the car tho but i put that down to the car being stood up for a while.

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ye got sum ethylene glycol based coolant, red stuff,

 

right ive put the thermostat in taken off the top coolant hoses and bled it from there ive now got heat :) i think it was just a big air lock

sadly it wasn't the simple heater flap. . cheers guys appreciate the help.

im gonna keep an eye on the water level now and make sure there's no leaks. and hopefully jobs a good en. .

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Fit a stock Toyota rad cap, the TRD run at a higher pressure which

you have no need for

 

ok cool, i forgot the trd cap is for a different engine lol :rolleyes:

 

i checked the water today and it hasn't gone down, but the circulation isn't very good i ran the car up to temp with the cap on and tbh it doesn't feel like theirs any pressure building in the system, Ive already booked it in for a new water pump and radiator cap so it will be sorted soon. the reason for the new water pump is purely cus the cam belt was done before i brought the car and im unsure whether the pump was changed or not so id rather be safe then sorry.

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  • 1 month later...
Its a long shot, but see post number 16 in the attached thread. I had the same sort of fault on mine: http://www.mkivsupra.net/vbb/showthread.php?49871-Heater-Maximum-Output-Temperature-Too-Low/page2

 

 

my heaters have been crap lately, searched on the forum and found this.

 

looked under my glove box and my rod was dis-connected too! :)

 

what a easy fix, that i would have never in a million years thought of looking. i assumed it was all digitally controlled due to the number of connectors behind the dash lol

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my heaters have been crap lately, searched on the forum and found this.

 

looked under my glove box and my rod was dis-connected too! :)

 

what a easy fix, that i would have never in a million years thought of looking. i assumed it was all digitally controlled due to the number of connectors behind the dash lol

i wasnt so lucky tbh i had mess about alot to bleed the system properly all done now tho cars been running sweet since, except the speed sensor showing a fault :-/

oh well will get it sorted soon enough :-)

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To help jiggle out trapped air you can run the car up to temp with the rad cap off

with the heater set to full hot and raise the revs on the engine from idle to approx 2500 rpm

then let it drop and repeat a couple of times.

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