Author Topic: Heater doesnt blow hot, and now has overheated, linked?  (Read 651 times)

Offline XRrich

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Heater doesnt blow hot, and now has overheated, linked?
« on: January 06, 2012, 03:20:14 pm »
Hi i have posted this in clubpolo and got some good responses but wanted to also check on here for some of your expert opinions.

Recently my heater has been going from hot to cold then back to hot for a few mins then to cold.
Now it constantly blows cold and on the way home the other day it overheated?

Any ideas what this could be due to?

I have changed the thermostat, although not driving since, i tested the old on in a pan of hot water and the thermostat was working fully before boiling point, opening fully.

People have said waterpump
other said head gasket
others said air in the system.

i havent drove it since it over heated just incase it was head gasket.

just wondering if i could find a way of diangosing it before actually taking things to pieces.

Thanks
Rich

Offline cheys03

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Re: Heater doesnt blow hot, and now has overheated, linked?
« Reply #1 on: January 06, 2012, 04:27:28 pm »
Sounds like waterpump in my opinion. Heater matrix is at the top of the system so a weak flow would invariably affect this first. Any air in the system would tend to get trapped at the top too. I'd probably spend the 15mins it takes to bleed the system as a last check before replacing the pump.

It's not loosing coolant I assume?

Offline XRrich

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Re: Heater doesnt blow hot, and now has overheated, linked?
« Reply #2 on: January 06, 2012, 04:46:09 pm »
nope not loosing coolant.. what is the proper way to bleed the system?

Thanks
Rich

Offline cheys03

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Re: Heater doesnt blow hot, and now has overheated, linked?
« Reply #3 on: January 06, 2012, 04:58:17 pm »
I've always done the following and it's been fine:

Set the heater to cold
Start engine
Get the engine hot unit the coolant fan kicks in
Open the heater to hot
Leave 5 mins
Open the bleed screw (white plastic tap the the heater matrix valve) any air will start to bubble out
Once there are no bubbles, close the tap.
Take for a quick drive with the heater still open
Bleed again for any air

Wait for engine to cool
Note coolant level and top up if required


Good luck! It'd be a nice fix if this were the cause

Offline XRrich

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Re: Heater doesnt blow hot, and now has overheated, linked?
« Reply #4 on: January 06, 2012, 05:45:16 pm »
Thankyou yeah it would be a very nice fix i will give it a go tomorrow