why is my heater not getting hot

[hotrodder13]

while driving in the rain today my heater was working fine. i parked up 6 hours later i was going home and my heater didnt get hot so i was freezing. the heather valve was fully open and still nothin. it did it a couple of months ago but it sorted it self out.
what can i do to fix it

thanks tom

[MColes]

When I picked my car up the other day I had this problem. So I flushed the heater - stuck a hose pipe on the end of the pipe that goes to the heater took the return pipe off that takes the water back into the engine and turned the hose pipe on. Should have see the muck that came out.

My guess is you have the same problem - a blockage in your pipes

While you're at it may as well flush the whole cooling system ;)

[hotrodder13]

ill have to have a try 2moro after work. luckly i dont need to drive there. thanks for the quick response

[Peetee]

Yep. I'd thoroughly recommend this solution. And make sure you flush both ways at least twice.

[Jefftav]

If your heater works sometimes and no others then could the thermostat be sticking open/closed? If you are flushing out the system it might be worth testing your thermostat?

[bmcecosse]

Maybe low water level ? Or head gasket leaking bubbles of gas into the system? Anytime my Rally Minor lost the heater - there was usually trouble ahead!
After the flushing - don't forget to add anti-freeze! And - realise that most of the stuff they sell these days is 'pre-diluted' - in other words - they are selling you mostly water! So you really need to fill with 100% antifreeze - unless you find a source of undiluted stuff!

[eastona]

yes, on an engine with no temp guage, the heater suddenly going cold is a dead giveaway for coolant loss.


if there's water in it, probably flush or thermostat. Probably best to do both, as if it's bunged up it generally gets into the thermostat. Cheap and easy to do, and can make quite a difference. Maybe fit a winter (88 or 92)one?

If it's never worked, check the valve is really opening properly and not vibrating shut. Mine was always a bit rubbish and it was only when doing the head I discovered the tap had been put on with hylomar/some kind of sealant which had made the hole really small and restricted water flow.

Andrew

[hotrodder13]

i drove it today and the heater didnt work again. after about 20 mins the heater got very hot and has started working again. i think that it might be the thermostat sticking. i do have a higher temp newer one. ill get a gasket for the housing and change it to see if it works normal.

thanks to everyone for helpin. still gona clean out the heater as well.

[RogerRust]

If the thermostat is sticking closed the heater will get very hot. The flow around the heater circuit relies on some back pressure to force the water uphill and round the heater loop. If you don't have a thermostat fitted the heater will be poor for two reasons firstly the water doesn't warm up correctly and secondly because the flow is poor.

So, if your thermostat is missing or stuck open it will affect the heater and conversely if it's stuck closed the heater will work until the water boils over and the level drops.

You can get a good idea if the thermostat is working by feeling the top radiator hose (the big one at the front of the engine). When you start the engine from cold the hose should stay cool and as the engine warms up then it should suddenly get hot when the stat opens. Be careful with your fingers near the fan and fan belt.

Another idea is to take the radiator cap off and see if any movement is apparent when it's cold the water should be still and flow should be obvious only when it's warmed up.

Only if it fails these tests would I try and change the thermostat which can be a lot harder than it looks!

My experience, for what it's worth, is that the things to do are firstly flush it well as described above and then to remove and clean the heater valve which gets full of muck and servery restricts the flow. Sometimes they fail completely.

Good luck.

[e-minor]

Hi All I had No heat at all coming from my heater so after reading some of the posts on here i decided to give the mog a flush i flushed the radiator both ways the engine and the heater matrix both ways and was amazed at the amout of Crud and rust that came out.This took a little longer than i had anticipated .I also changed the newer style pull cable heater valve for the older style brass stopcock style.The heater now gets toasty warm and will keep the windscreen from misting over which was a major pain,my next job is to see if i can get a mini fan in there to try and get the heat moving around a bit better ..But the flushing alone made all the difference,,,

cheers

e-minor

[xpress]

will flush my hoses too. Thanks all.