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Cooling System Problems
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Rootes75



Joined: 30 Apr 2013
Posts: 2960
Location: The Somerset Levels

PostPosted: Thu May 30, 2019 5:58 pm    Post subject: Cooling System Problems Reply with quote

Well, another set back with the Commer lorry. I have had a new thermostat housing machined, its now fitted and all the pipework is tightened and the coolant topped up.
We started her today and left her running, after 10 minutes water started pouring out the radiator cap?? We had a look and this water was cold!?!
I checked underneath and the thermostat housing and pipes were hot meaning the thermostat had opened and hot water had gone through it.
I checked the bottom pipe and again this was hot meaning fluid was passing. But, we then noticed the radiator itself was still cold, it was only hot at the top and just round the bottom hose, nowhere else.
We tried again and this time with the rad cap off, after 10 minutes we noticed the water in the header tank rise and overflow through the cap again. But again the water overflowing was cold!?!
We are thinking its a blockage in the radiator of some kind?
Any ideas or remedies?
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1937 Hillman 80
1946 ERF C.I.5
1947 Hillman Minx
1955 Hillman Minx Mk8
1950 Commer R541
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roverdriver



Joined: 18 Oct 2008
Posts: 1172
Location: 100 miles from Melbourne, Victoria, Australia

PostPosted: Fri May 31, 2019 7:57 am    Post subject: Reply with quote

I had a car that did that. Reasoned that the thermostat remained closed until engine warm, as it should, but while that happened air or steam built up behind the thermostat. As soon as the thermostat opened the air pocket (or steam pocket) forced the water above to overflow.

Once the radiator had regurgitated, the water level remained constant until the next cold start.

Solution was to drill a very small (1/16 inch) hole so that any gas created within the engine could slowly leak past the thermostat before the thermostat opened. Older units had such a hole, but it seems that a lot of modern ones don't.
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Rootes75



Joined: 30 Apr 2013
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Location: The Somerset Levels

PostPosted: Fri May 31, 2019 11:30 am    Post subject: Reply with quote

The thermostat has a very small hole that I think does that, before the bellows open it allows steam through that hole. It could be something to do with that but I still wonder why the radiator isn't fully hot and the water overflowing is cold?
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1937 Hillman 80
1946 ERF C.I.5
1947 Hillman Minx
1955 Hillman Minx Mk8
1950 Commer R541
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MVPeters



Joined: 28 Aug 2008
Posts: 717
Location: Northern MA, USA

PostPosted: Fri May 31, 2019 7:21 pm    Post subject: Reply with quote

The symptoms are certainly of a clogged radiator core. Easy enough to test by disconnecting the top & bottom rad hoses & use a garden hose to back-flush it for 30mins or so & see what you get & go from there.
If there's a lot of crud, ideally I'd remove the t'stat for a while.
Radiator flush fluids are available, but white vinegar is an inexpensive alternative; just leave it overnight & then flush thoroughly.
(early t'stats had a 'jiggle-pin' in the little hole to prevent it clogging - it's more for letting air bubbles out rather than steam).
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Farmer John



Joined: 18 Feb 2010
Posts: 172
Location: Manawatu NZ

PostPosted: Fri May 31, 2019 10:34 pm    Post subject: Commer cooling Reply with quote

Hello. Two possibilities. First the most likely from your description is that combustion gas is entering the motor somewhere and slowly building up somewhere hot. That part of the motor is not cooled by the accumulated gas and gets hot enough or enough gas accumulates that the pressure builds sufficiently to force the cooling system to reverse (the thermostat is shut) and push coolant back up through and out the top of the radiator. To diagnose, remove the thermostat housing, fill to that level, remove the fan belt and run the motor. If bubbles appear or it overflows more than you expect from coolant expansion you have confirmation that combustion gas is getting into the coolant.
The other possibility is the radiator being blocked. To check, fill it, leave the cap off and then release the water from the bottom hose fitting. Water should really gush out. How quickly should it empty? You can only judge that from experience unless you could time a known good one and compare.
Even more basic, if the bottom hose is off you should not be able to overflow the radiator by filling it with a water can.
My opinion. I would not hesitate to have the radiator flow tested and dismantled and cleaned. You need to know that the radiator is contributing nothing to any other problem, it would not matter at all if the radiator was found to be as good as new inside, I just want to be sure.
So do that anyway.
Congratulations on your restoration it has been a massive effort. Trucks (lorries?) are another whole level from cars, well done.
John
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Rootes75



Joined: 30 Apr 2013
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Location: The Somerset Levels

PostPosted: Fri May 31, 2019 11:32 pm    Post subject: Reply with quote

We are having another go at it tomorrow. Will try out some of the tips.
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1937 Hillman 80
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1947 Hillman Minx
1955 Hillman Minx Mk8
1950 Commer R541
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Rootes75



Joined: 30 Apr 2013
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Location: The Somerset Levels

PostPosted: Sat Jun 01, 2019 4:55 pm    Post subject: Reply with quote

Well, we have finally done it!

Firstly we took off the lower radiator hose and drained the radiator, plenty of dirty water came out, definately not oily. We then left the hose off and flushed it through, dirty water continued and we carried on till it ran clean. We then fitted new hoses and filled up with water, this time we didnt fill it into the expansion tank which was our mistake before.
Another issue we found was that the cap fitted metal to metal and there should be a rubber seal, by chance I have a header tank off a later fire engine and upon looking we found an intact seal! We soaked it first before carefully removing it and fitting it to ours.
We then started the engine and kept fingers crossed, she ran for a good 20 mins and we kept checking the pipes, they got hot top and bottom and this time all the bottom and top of the radiator was hot. She did not overflow!
We also noticed that usually when she stops you can hear gurgling/gulping noises come from the system, not this time though, she was lovely and quiet! There must have been an airlock in the system.
All in all a very good weeks work on the lorry, next step is to try her out on the road and do some fine tuning with the carb and timing.
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1937 Hillman 80
1946 ERF C.I.5
1947 Hillman Minx
1955 Hillman Minx Mk8
1950 Commer R541
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Rick
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Joined: 27 Apr 2005
Posts: 21314
Location: North-west UK

PostPosted: Sat Jun 01, 2019 6:00 pm    Post subject: Reply with quote

Excellent, glad to hear that it was nothing more sinister/expensive.

RJ
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Rootes75



Joined: 30 Apr 2013
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Location: The Somerset Levels

PostPosted: Sat Jun 01, 2019 11:29 pm    Post subject: Reply with quote

So were we Rick, fingers crossed we have solved it.
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1937 Hillman 80
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1947 Hillman Minx
1955 Hillman Minx Mk8
1950 Commer R541
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Rootes75



Joined: 30 Apr 2013
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Location: The Somerset Levels

PostPosted: Thu Jun 20, 2019 11:27 am    Post subject: Reply with quote



Thought you might like to see the new Thermostat Housing.
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1937 Ford 7w
1937 Hillman 80
1946 ERF C.I.5
1947 Hillman Minx
1955 Hillman Minx Mk8
1950 Commer R541
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peter scott



Joined: 18 Dec 2007
Posts: 6297
Location: Edinburgh

PostPosted: Thu Jun 20, 2019 12:11 pm    Post subject: Reply with quote

Your new housing certainly "looks the business".

Peter
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