Heater Issues

Discuss mechanical problems here.
Forum rules
By using this site, you agree to our rules. Please see: Terms of Use
Post Reply
CharlieW
Minor Friendly
Posts: 13
Joined: Sun Jun 28, 2020 10:54 am
MMOC Member: No

Heater Issues

Post by CharlieW »

Hi all
We have been experiencing a problem with the heater on our 67 Morris 1000. When running the engine, with heater valve open, the inlet hose to the heater gets hot. The outlet hose only gets hot, and heater works, if the revs are kept high. When revs return to normal tick over speed the outlet hose gets cold but the inlet hose remains warm - heater doesnt work.
We think there maybe an air lock in the heater but not sure of the best way to remedy. We have recently fitted a new Radiator Cap. This replaced the incorrect one previously fitted (it was the wrong size). The system never seems to pressurise with either cap. Could this be caused by an air lock in the system or something more sinister..

As usual any advice is greatly appreciated.

Thanks

Charlie
mowogg
Minor Fan
Posts: 356
Joined: Mon Oct 22, 2007 9:45 pm
Location: Chichester West Sussex
MMOC Member: No

Re: Heater Issues

Post by mowogg »

Hi

Sounds like it might be a blockage. I think if it was me I would try flushing through the system.

Do you know any history? I know radweld or similar can cause this.

I would drop the water level a little in the radiator and then take off both the inlet and outlet pipes from the engine. I would then use a hose to back wash it to see what comes out.

Remember to catch the flushing as antifreeze is not supposed to be too good for pets/animals.
pgp001
Minor Addict
Posts: 667
Joined: Sun Aug 27, 2017 6:05 pm
Location: West Yorkshire
MMOC Member: Yes

Re: Heater Issues

Post by pgp001 »

My heater was worse than useless, so I took both hoses of the engine end connections and stuck the garden hose in one of them whilst the other was in a bucket.
I was amazed at how much brown sludge came out, i kept reversing the water flow though it until it ran clean, the reconnected it.
My heater now works way better than the one on my modern car.
I have never had problems with air locks in it though.

Phil P
oliver90owner
Minor Legend
Posts: 1653
Joined: Thu May 12, 2016 6:33 am
MMOC Member: No

Re: Heater Issues

Post by oliver90owner »

From the description of the problem it would appear to be a flow problem, possibly within the heater matrix.
Edward1949
Minor Fan
Posts: 158
Joined: Fri Mar 30, 2018 1:21 pm
MMOC Member: No

Re: Heater Issues

Post by Edward1949 »

Stating the obvious, but is the heater valve fully open?
MCYorks
Minor Fan
Posts: 176
Joined: Thu Jan 23, 2020 10:18 pm
MMOC Member: Yes

Re: Heater Issues

Post by MCYorks »

Are the heater hoses connected the correct way round? I once had poor heater output and found the hoses had been fitted the wrong way round. I was amazed at the difference it made :D

Alternatively, the heater hoses can sometimes collapse inside but look fine from the outside. This can cause a flow restriction and reduce the heater output. New hoses are the best fix. You could also check water is flowing freely through the metal pipe on the engine and into the radiator bottom hose.

To prevent airlocks, I usually remove the hose from the heater valve, hold it up in the air and use a jug to fill it. Then put my thumb over the end to prevent water loss and quickly reconnect it to the heater valve. All with the cooling system cold of course! Never had any problems with airlocks in the heater doing it this way :D
CharlieW
Minor Friendly
Posts: 13
Joined: Sun Jun 28, 2020 10:54 am
MMOC Member: No

Re: Heater Issues

Post by CharlieW »

Hi everyone - Thanks for all the replies.
To be honest we have tried all these suggestions. Earlier today we removed rad top and bottom hoses and gave it a good flush out - it was pretty clean. We also removed heater hoses, flushed and back flushed. I was hoping to see a lot of gunge come out but again it was very clean. At this stage we assumed the problem was an air lock so proceeded to refill slowly with heater valve open.
The forum and other sources say the system takes 5.5 litres (with anti-freeze) allowing for the heater. However we could only get about 3/4 of this into the car. Once the car was warmed up we had the same issue with the heater - inlet hose hot, outlet hose cold. The outlet hose and heater only got warm with a bit of extra revving - like before. Then suddenly the inlet hose lost heat completely and never came back. I removed the outlet hose again and the pipe was empty. Again the system didn't achieve any pressure. So we are sort of worse off than before.
A bit of background to the car -
*My dad and I bought this car around 14 years ago.
*We enjoyed it, did a bit of work on it then then it was garaged for about 10 years.
*We have been tinkering on it since last summer and got it back onto the road recently.
When we first got the car we replaced the heater valve and hoses. it was that long ago but we do remember flushing everything out at the time. The car has done little to no miles since. The heater was working previously. We recently removed the heater hoses to fit new grommets. It was after this we had the issues.
Everything looks connected up correctly and there is no blockage on the metal outlet pipe to the rad bottom hose as suggested by McYorks.
I'm wondering if pressure from the garden hose wasn't high enough and there is still potentially a blockage somewhere. Would any of these issues be due to a faulty water pump? This wasn't replaced by us. The heater valve was definitely working before as the heater inlet pipe was very hot and cooled down once the valve was closed. I guess it could have failed today in addition to the other issues - however its hardly been operating since we replaced it. We are not too keen on taking the car very far in case this is a sign of a more serious issue.

Neither of us are mechanical but were both fairly technical and would have a go / investigate most things. We are not too sure what to try next.

As usual any more tips would be greatly appreciated.

Ta

Charlie.
biomed32uk
Minor Addict
Posts: 630
Joined: Mon Feb 03, 2014 5:16 pm
Location: Gt Holland, Essex
MMOC Member: Yes

Re: Heater Issues

Post by biomed32uk »

Long shot but it may well be worth pulling the water pump off and seeing if the impeller is still there, I have heard of them corroding away.

I've never had issues with air locks in the minor at all, just leave the rad cap off and burp it.
kevin s
Minor Legend
Posts: 1376
Joined: Tue Mar 26, 2013 8:20 pm
Location: Chelmsford, essex
MMOC Member: No

Re: Heater Issues

Post by kevin s »

Have you checked what mcyorks suggests?

On one of my cars (TR7V8) the heater is hopeless if the hoses are the one way round and roasting if the other, the feed from the cylinder head goes to the bottom of the heater matrix and the return to the bottom hose the top, thermodynamics say you should feed in the top and draw the cool water out the bottom but I have found air gets trapped if the return is at the bottom and by putting it at the top air is drawn through with the flow of water and purged out the top , I have plumbed the minor the same and that works well too.
MCYorks
Minor Fan
Posts: 176
Joined: Thu Jan 23, 2020 10:18 pm
MMOC Member: Yes

Re: Heater Issues

Post by MCYorks »

biomed32uk wrote: Mon Apr 05, 2021 7:40 pm Long shot but it may well be worth pulling the water pump off and seeing if the impeller is still there, I have heard of them corroding away.
I think biomed32uk's suggestion is definitely worth checking. The radiator will thermosyphon to a certain extent, but the heater needs the water pump to work effectively. The impeller could well be very corroded or clogged to the point that it's not shifting much water. You said the car has been garaged for 10 years. My Minor was stood for a long time and corrosion in the pump completely blocked the inlet :o So it may be worth pulling the bottom hose off the pump and checking if the pump inlet is clear. At least water pumps for the 1098 are cheap :D

A garden hose should provide enough pressure clear most sediment. So, I think you've established the heater matrix, radiator and hoses are all reasonably clear. Maybe one last thing to try before checking the pump. Have you flushed the engine? Connecting the garden hose to the heater valve and flushing with the valve fully open, should clear any sediment that's possibly blocking the back of the head.
win
Minor Fan
Posts: 253
Joined: Mon May 04, 2009 5:41 pm
Location: M1 J36
MMOC Member: Yes

Re: Heater Issues

Post by win »

IMG_20201218_150358718.jpg
IMG_20201218_150358718.jpg (3.22 MiB) Viewed 1272 times
This is a little bit of kit I rigged up to flush mine out.
It is just an old central heating pump connected up using bicycle inner tubes, with stiffer pipe inside.
You can add flushing or cleaning solution, and leave running for a period.
Obviously best to remove the thermostat.
Radiator is done separately.
Regards Win
Image
South Yorkshire
CharlieW
Minor Friendly
Posts: 13
Joined: Sun Jun 28, 2020 10:54 am
MMOC Member: No

Re: Heater Issues

Post by CharlieW »

Thanks for all the replies.
We will try all the suggestions at the weekend. Unfortunately work commitments restrict me to weekends.
We haven't yet flushed the engine or checked the pump - so that will be next. Due to the length of time its been sitting its probably prudent to change the pump, thermostat and any older hoses.
I'll update our progress at the weekend.

Again - We really appreciate the advice.

Cheers

Charlie
Post Reply