Car Heater Problem

[bednobs]

My car has suddenly stopped heating up till i've been driving for at least 25 minutes. Does that sound like smething expensive to fix?

[Hymie]

Check the engineer coolant level – often the cabin heater matrix the highest point in the cooling system.
If there is insufficient coolant in the system, coolant may not be reaching the cabin heater matrix.

[Hopkirk]

There is probably a thermostat that is supposed to keep the heat in the engine and cabin heater until it reaches full operating temperature. Only then should it release heat into the radiator to be dispersed.

If your thermostat has failed heat is going straight to the radiator, severely slowing the engine teaching temperature and hearing the cabin.

Not an old Vauxhall Astra is it? They were notorious for this a few years ago.

[bhg481]

The most likely thing is a failed thermostat. It sits at the top of the radiator and stops the coolant circulating until the temperature rises; if it fails in the open position the engine takes longer to heat up. It's a cheap enough item to buy and also cheap for a garage to replace it.

[Hopkirk]

.. reaching ... (not teaching)

[mjwman]

Thermostat. Have you noted the temperature gauge not reaching normal?

[bednobs]

no, temp gauge is as usual

[Hopkirk]

Does the gauge move up to normal quickly after starting? If it takes longer than normal then it suggests a thermostat problem.

If it raises as normal there is a different problem.

[bednobs]

Raises normally

[bhg481]

Just to clarify; you are saying the temperature gauge rises at the same speed as it always has but the heater takes about 25 minutes to start working.

[Ryzen]

Sounds like a blockage or air lock in the heater matrix.

[bednobs]

Thanks for all the help. The thermostat has now started going up to 130 degrees and pinging at me si I've bittrn the bullet and booked it in

[davebro]

very expensive - you need to buy a Toyota! :-))

[ZebuSanctuary]

// **thermostat has now started going up to 130 degrees //

Presumably you mean **temperature gauge.

Very wise!

A standard radiator cap has a sealing pressure of 15 psi above atmosphere. This allows for the coolant (assuming water with no antifreeze) to rise to 257 °F. This equates to 125 °C.

Your engine should not be running on this temperature limit. Since you have said 130 °C. At best you're cooking the head gasket. At worse... Hopefully you will get away from having caused any serious damage!

[bednobs]

for completeness; thanks for all the help.
It was a cracked coolant housing by the gearbox, causing loss of coolant over a longish period. I am having the housing replaced, and in the meantime have refilled and am checking coolant before each journey (well, my husband is)

[bhg481]

Thanks for getting back to us. Not everybody bothers but it does help us to try to sort out problems for others.

[bednobs]

BHG - i note from reading back hymie gave me the correct answer in the first instance ;)

[bednobs]

and in fact i didnt do his (very easy!) check. GRRRRR

[bhg481]

Most modern cars have a transparent overflow bottle which makes it easy to check the coolant level (you used to have to wait until the engine was cold and remove the cap). I think I took it for granted that you'd looked at the level - you'll know next time.

[bednobs]

my onlt excuse is that i can't get my bonnet up :)

[Tilly2]

That's a reason, Bednobs, not an excuse.

Glad you got it fixed.