Heater Not Heating

[igdirect]

Hi All,

Soon after having the head gasket replaced on my GS300 Mk1, I noticed that the heater was barely working. AC was OK for cooling but on cold days the barest amount of heat blows through the vents.

More oddly, if I turn the temperature selector to 30degC, there's no change in the fan speed at all, even on a day when the temperature was only 4 degC - it stays on low.

So, no problem for temperatures of 20 or less, but no additional heat or fan response for anything higher.

No problem with radiator or engine cooling - guage needle dead centre.

Airlock? Sensor problem?

Any advice welcome.

Regards,

Ian

[Zee007]

Thermostat maybe?

[Monster-Mat]

airlock

[randyreindeer]

I don't want to sound pessimistic but has your gasket been changed or has some dodgy garage just whipped out the Thermostat?

[crazylex]

airlock

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Thats what I'm thinking too

[MacRS200]

airlock

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Thats what I'm thinking too

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Yup agree the the above I would say air lock in the heater matrix

[norkep]

Had the same problem but after a removed the rad, it's due to an airlock, not the easiest things to remove airlocks on either, took me quite a few attempts on bleeding the rad before I started to feel hot air, took about 2 Ltres of coolent before I managed to remove the airlock.

[eXOBeX]

Would being parked facing up a steep hill help when trying to remove the airlock?

[Mr Morse]

Would being parked facing up a steep hill help when trying to remove the airlock?

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On a rear-engine car, yes - the MR2 is a real PITA to do.

Try loosening the rad cap 1/4 turn to the first click and run the engine for a few mins until warm. This allows the system to breathe at atmospheric pressure and should allow any air to escape.

[eXOBeX]

Would being parked facing up a steep hill help when trying to remove the airlock?

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On a rear-engine car, yes - the MR2 is a real PITA to do.

Try loosening the rad cap 1/4 turn to the first click and run the engine for a few mins until warm. This allows the system to breathe at atmospheric pressure and should allow any air to escape.

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My thinking was that having the rad cap at the highest point in the whole system would allow air bubbles out. Being at such an angle would also put the heater matrix lower down in the system, also the angles of all the hoses would be different, hopefully allowing air to escape, etc.

[Monster-Mat]

to remove the airlock in the cabin heater matrix.

run the engine with the heater fans on full on full heat.

switch of the engine, and let it cool enough to be able to remove the cap, top up.

start the process again, continue untill heat is felt in the cabin.....

its best to drive the car to get it upto heat

[crazylex]

Or get it up like this

Did actiually get it a fair bit higher during the process of bleeding it. just to make sure the cap was well above the top of the heater matrix.

[norkep]

Your brave, not sure I'd do that to mine

[igdirect]

Many thanks for all the suggestions! I'll give them a try this weekend and let you know!

Now all I've got to do is find a forklift on eBay...

Cheers!

Ian

[crazylex]

Your brave, not sure I'd do that to mine

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Yeah I was bricking it when it was right up.

Cant remember why we had a block and a brick under it ?

A few people driving past on the estate did a double take.

To be honest we are used to lifting heavier, more expensive and more delicate machinery so it was a doddle really. Only problem was as it went up, because the handbrake was on, the front wheels started to roll up from between the forks and onto the back fork. A scary moment for sure.

If you up near Leeds we can do it for you :winky: but maybe theres a safer way.

[eXOBeX]

If you up near Leeds we can do it for you  :winky: but maybe theres a safer way.

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What, like a hill you mean? :P

[igdirect]

Problem solved! :D

Not an airlock or sensor fault, but the control cable to what I assume to be the heater matrix bypass valve had not been reconnected. It's the small box on the firewall in the picture - the guilty cable runs from left to right and simply hooks onto a metal lug on the valve.

Bring it on, Winter...

Cheers!

Ian

[Tony9r]

Problem solved!  :D

Not an airlock or sensor fault, but the control cable to what I assume to be the heater matrix bypass valve had not been reconnected.  It's the small box on the firewall in the picture - the guilty cable runs from left to right and simply hooks onto a metal lug on the valve.

Bring it on, Winter... 

Cheers!

Ian

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Great news mate... such an easy fix too :P

[igdirect]

I should have said that I had great fun trying the airlock fix first.

First attempt to lift the front end was with a trolley jack. No good, still no heatflow (and, of course, I hadn't spotted the loose cable yet).

So, in the absence of a forklift I set off to find a hill.

Easier said than done as I live in the Lincolnshire Fens and trying to find a hill was like trying to find a needle in a haystack. I finally ended up on a remote backroad, blocking a narrow humpback bridge and hoping no-one would come along for the next 10 minutes or so! Two bemused / irate tractor drivers and car moves later, still no joy.

Got back home, and decided to see if the heater matrix inlet and outlet hoses were OK. And there it was, the little b****r, taunting me... <_<

On goes the cable, and out comes that lovely heat.

Moral of the story - check your cables before you annoy busy farmers on narrow bridges.

Ian