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Re: Overheating

Posted: Sat Dec 29, 2018 5:31 pm
by Ian Jones
Failed constant voltage supply to gauge?

Regards

Ian

Re: Overheating

Posted: Sat Dec 29, 2018 6:21 pm
by panky
If you can put your finger in the radiator water then it doesn't look like the thermostat was actually open. How long was the engine running for? It may have been that the heater matrix was doing all the cooling required and the stat didn't have time to open, try another run with the heater valve just cracked open.

Re: Overheating

Posted: Sat Dec 29, 2018 9:16 pm
by Victorplum
The engine was running for a good 20 minutes. It was reading past 140c when the coolant in the radiator was still cold. The heater in the cabin was toastie by this time. Should I be replacing the water pump?

If I almost shut the valve the water will leak. Do I need to replace the valve maybe?

Re: Overheating

Posted: Sat Dec 29, 2018 9:44 pm
by paul 300358
When you flushed the radiator, did you remove it from the car and flush both ways? Sounds like a blocked rad.

Re: Overheating

Posted: Sat Dec 29, 2018 10:14 pm
by Victorplum
I didn’t physically remove the rad but I did flush both ways until clear.

Re: Overheating

Posted: Sun Dec 30, 2018 6:39 am
by Sleeper
Dirty/suspect in-line connections battery-sender-gauge ? Causing extra resistance in circuit?

John :wink:

Re: Overheating

Posted: Sun Dec 30, 2018 9:04 am
by Nickol
Time for me to jump in.
You seem to have established that the engine itself is not overheating by taking readings with the infra red gun. Is that right? Thus, although it seemed to be working correctly before, the gauge or its feed must be the culprit and the slight leakage at the valve cannot be significant.

I had/have a similar problem , albeit that my gauge was new and so to the sender unit. It always read very hot at the extreme end. Like yours 140°. It was suggested that the sender unit was incorrect ( there are a couple of possible units you can get) but in your case it was working before and unlikely to have gone kaputt. It may though not be earthing properly and the new coolant you put in is very viscous. I put some in my old Austin 8 and it leaked out of the radiator even though using pure rainwater, there was no leakeage.

I would remove the sender my self, clean it up and put it back. You can also check its resistance with a meter when it gets hot to see if it reads correctly. In my case I could never achieve the proper gauge reading ( bear in mind that allmy components were brand new) so I cheated and put a resistor - I think it was 30 ohm - in the wire and now get normal readings on the gauge.

Declan burns sent me at the time this informations

The standard temperature sender for Smiths instruments is GTR 101 or Intermotor part no. 5271. It has a 5/8" UNF thread-don't go overboard on tightening it. The resistance is 800ohms @20°c and 50ohms @90°C-

Re: Overheating

Posted: Sun Dec 30, 2018 9:18 am
by philthehill
As regards the heater tap/valve.
What you have is cheap and cheerless as it has no proper gland seal around the tap stem which can be tightened or adjusted - therefore once you have a leak you might as well throw it away. I suspect that it has a 'O' ring for a seal which has failed - therefore the source of the leak.

This is the type of heater tap/valve that you need :-

https://www.ebay.co.uk/itm/Morris-Minor ... :rk:8:pf:0

There is a gland seal around the tap stem (held in place by the nut under the wheel) that can be adjusted and tightened as required.

The gland seal should be lightly oiled to keep the gland seal in tip top condition.

Re: Overheating

Posted: Sun Dec 30, 2018 9:43 am
by Victorplum
Yes, I took the temperature reading from the engine block. It read 58c after around 20 mins (stationary) I take it that this is an acceptable reading and that when it goes to 82c the stat will open for the coolant to circulate?
I have a friend coming to stay for new year tomorrow. He is always tinkering with his old mk1 escort. I’ll ask him about cleaning the sender unit as I’m not sure where that would be.

It’s a relief to know that I’m not overheating the engine and I can go on driving and ignore the gauge :)

I’ve ordered a new heater valve via the link on eBay. Thank you very much for that. And thank you to everybody for your help. I would be lost without it.

Re: Overheating

Posted: Sun Dec 30, 2018 10:19 am
by myoldjalopy
Symptoms of overheating (especially if it were really 140 degrees C) are 'bumping' noises from the coolant boiling in the system, the cap blowing off and boiling hot water gushing out. Your engine would also be sizzling and very hot to the touch, with a smell of hot oil. As you are not experiencing any of these symptoms, and the car is driving OK, then the guage is giving a false reading for some reason, as others have pointed out.

Re: Overheating

Posted: Sun Dec 30, 2018 2:19 pm
by Chipper
Sleeper wrote:
Sun Dec 30, 2018 6:39 am
Dirty/suspect in-line connections battery-sender-gauge ? Causing extra resistance in circuit?

John :wink:
If there was too much resistance, the gauge would never actually reach full scale deflection (i.e., 140 degrees in this instance).

I suspect the gauge may not be wired via the voltage regulator (a little metal canister attached behind the fuel gauge on the back of the speedometer), hence when the battery is fully charged at say, 14V, it is directly driving the gauge at 'full pelt' rather than the 10V or so that would normally be used to feed a gauge from the voltage regulator.

This article explains it's operation:
http://www.wheels-alive.co.uk/need-to-k ... tabiliser/

Re: Overheating

Posted: Sun Dec 30, 2018 4:33 pm
by philthehill

Re: Overheating

Posted: Sun Dec 30, 2018 5:21 pm
by Nickol
Victorplum did not say he had rewired anything so if the gauge was working correctly before it should work still. In any case, the fuel gauge also takes current from the volt reg which, if faulty would also read incorrectly.

Perhaps he can tell us what ohm readings he gets ?

Re: Overheating

Posted: Mon Dec 31, 2018 9:22 am
by kennatt
it's obviously the gauge or sender on the block,if it was that hot the water would be boiling out of the filler and the pump is working,because if not the same boiling would happen,but to check the pump,let it warm up with the rad cap off and keep watching the water in the top of the rad. When the thermostat opens you will see the water start to move,rev the engine and if pump is ok you will see the level drop slightly as it pulls water through the system.But from your posting I would say that it definitely is not overheating.