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Temperature gauge and electric fan


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Hi folks, I have just taken delivery of my TR3 - so be gentle with me as I start asking numpty questions!!

 

On a run earlier this week the temperature gauge was reading 185 or thereabouts, rising a little in traffic. Thermostatic fan cut in and cooling was working. On the return home once switched off she spewed the contents of the expansion bottle on the garage floor.

 

The next run out today the gauge remained firmly up against the stop pin - at the cool end of the scale! The fan did not cut in on the run nor did she vomit when switched off. I began to get suspicious that all was not as it should be.

 

I left her on tick over to warm up. Coolant began to fill expansion tank and just before it overflowed again I chickened out and manually operated the fan. The coolant level in the expansion bottle immediately started falling.

 

I suppose I should have continued to make sure the fan thermostat works. Am I being too chicken? The fact that the coolant level dropped suggested to me that the fan (at least on manual) and thermostat are OK

 

I do want to make it to Malvern next weekend!

 

Can anyone help with a diagnosis? The temperature gauge is of the capillary type (as far as I can see i.e. no wires from the sender unit in the thermostat housing)

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The gauge not rising could have been a result of so much coolant volume being puked the day before that the level was below the gauge bulb in the t-stat housing.

 

With an overflow bottle in place -- I'm assuming that's what you have, rather than a pressurized expansion tank, but it would be good to know for sure -- the coolant level should be right up to the cap seat in the neck of the radiator. If it overflowed a lot it might have sucked in air on cooling.

 

Did you top off the coolant level after the overflow?

 

An overflow bottle will work pretty well at about half full when cool. Make sure the hose extends to the bottom of the bottle.

 

What pressure rating do you have on radiator cap? Is it an original style radiator with long-reach cap seat?

 

Mixture and timing can affect operating temperatures. If it consistently overheats be sure these are in spec.

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Don, thanks for your swift reply.

 

Confirm an overflow bottle.

It may well have sucked air in on cooling

I did top up with coolant to the neck just below pipe to the expansion bottle

The Radiator cap is odd - to my mind - as it has no spring relief valve (But the car has had a rallying career and no expense has been spared on its fettling so I have to assume the system worked prior to my acquisition last week!)

Just taken some pics (hopefully attached!). Expansion bottle now has a couple of inches in the bottom (pipe reaches the bottom)

 

 

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Ben -

that cap says 'Evans' which is 100% glycol and the cap has no pressure spring which is correct for such a system, as it does not need to be pressurised because the boiling point of the fluid is high compared with water. There are very different opinions as to the merits (or otherwise) of that stuff though. What have you been topping it up with ? Is it possible there is water in there despite the warning on the cap ?

 

Rob

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Thanks all, I have been topping up with Evans. I have absorbed the opinions about it on here. I have inherited the system so will stick for the moment!

 

How do I get rid of an airlock? I read somewhere on here about raising the front end of the car.

 

......do I have to pat its back to get it to burp!!

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The whole point of waterless coolants like Evans is that the temperature of the engine can get much higher without boilover. Put me firmly in the not-on-MY-car camp. I run water+ethylene glycol, and can't give any reasonable advice about making a waterless system that's apparently boiling over.

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I have found that by 'squishing' the longer hoses as much as you can (with the engine off of course), trapped air can be made to move. Then run it for a bit to circulate the coolant and squish again - repeat until no more air comes out. I guess raising the front a bit may help as long as the filler neck stays the highest point. The question is though - if that was the cause of the first coolant loss how did the air get in there in the first place ? Did the PO do some work on the cooling system before you got the car perhaps ?

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I've not read the comments on here about Evans, so forgive me if I've missed something, but in all that I've read about it I've never seen the advice to do away with a pressure cap to seal off the system when using Evans. Either way, Drewmotty raises a very valid point - there should definitely be a rubber seal under the cap to stop air being sucked in around it when the coolant cools down (it needs to be absolutely sealed so that it sucks coolant back up from the overflow bottle, rather than air in around the cap).

I also don't see any reason why you shouldn't fit a normal pressure cap to help to keep the coolant in place. A system with an overflow bottle like yours would normally be fitted with a conventional pressure cap and the rubber seal around the outer lip to stop air being sucked in. It definitely sounds like airlocks are your problem, and as Don says, the temp gauge not rising may have been due to the coolant level being below the temperature gauge bulb.

Unfortunately replacement radiators sometimes (possibly always!) have the filler neck at slightly too shallow an angle, dropping the filler height half an inch or so lower than it was on original rads - I know because I hit this problem when I replaced the rad on my TR2 before a big rally 15 years ago - and it ran hotter with the new rad than with the old one plus it had a tendency to airlocks that it didn't have before - a real pain. Especially with Evans in the system, I would try running the engine with the rad cap off and squeezing the hoses while it's running to try to shift airlocks. Just don't get your fingers in the way of the fan.

Malcolm

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Thanks Malcolm, I have had a "squishing" session but with no success so far. I will try again.When the fan is on the level in the expansion bottle drops as it is draw into the radiator. But I too am deeply suspicious about the rad cap!

 

As I understand it the temperature sensor is in the thermostat housing which must surely be getting bathed in hot coolant. It is still not twitching!

Edited by Ben Freer
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Yes Ben the temperature sensor is in the thermostat housing - its the thing which is connected to what looks like a thin pipe with a wire wrapped around it. Given that it was working before the coolant loss it does seem you must have air in there, unless you have been very unlucky and suffered a gauge faliure too. I wonder whether it might be worth loosening the top of the bypass hose slightly (the one just above the sensor which goes down to the pipe on the near side of the engine) just to see whether you can let any air bubble out.

 

Rob

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One way of getting air out the system is to fill it with whatever coolant you prefer and then warm up the engine with the filler cap off. Sometimes this air blockage will get pumped through till it gets to the filler box. Because the cap is off, the air escapes. Top it up to where you like it, put on the cap and you should have not any future trouble with air blockages.

 

Don Elliott 1958 TR3A

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An update:

 

I have got a new rad cap coming. Also a new thermostat just in case that is adding to the issue.

Did some more squishing of hoses and disconnected the top hose - there was a small "gloop" noise so I think some air escaped.

Took her for a run but temp gauge still not working.

 

.........back to squishing hoses to get some more air out!................. Rad cap should be here tomorrow.

 

Really appreciating your advice on here! (My TR6 was never this cantankerous!!)

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Ben, to be honest I fear the cantankerous part is the Evans coolant... It is definitely gloopy when cold and that can be an issue in older engines. I've heard from a Jag XK 120 owner that Evans admitted to him that it is not compatible with the original water pumps on early XKs, and I believe this issue was related to its high viscosity when cold. I suspect that is making it more difficult for you to get rid of the air bubbles - hence the suggestion to run the engine gradually up to temperature with the rad cap off, so you can see what's going on with the coolant and hopefully the squishing of hoses will be more productive as the coolant warms up and the viscosity reduces.

Good luck!

Malcolm

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Another update in my mini-saga!

 

I made her a nice hot cup of tea - without a tea bag or milk! - and dunked the temperature sensor in the mug. Not a glimmer of a twitch on the needle.

 

So my conclusion is: not an airlock issue just a dead temperature gauge.

 

The "vomiting of coolant" I think was the result of the expansion bottle being overfull in the first place and it having no where to go - not a boil over

 

So I will top up with coolant and drive to Malvern with the fan on manual keeping an eye on oil temperature and sniffing for signs of overheating.

 

So I now need a replacement temperature gauge....................anyone know where I can get mine repaired/get a replacement from?

 

Many thanks for all your advice and moral support - hopefully see some of you at Malvern .................. as long as we get there of course!! ;)

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Thank you Stuart. I can see that my previous comment about TR3's being "TR£'s" is ringing true already! :wacko::P

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Final report:

 

Sorted (subject to surviving the Wessex Club run at the weekend). It was a combination of factors. Coolant system overfilled which then overflowed from the overflow bottle. Kenlowe fan is not thermostatically controlled just manual which explains why it got warmer ticking over after a run. The temperature gauge was fine when I collected the car but snuffed it on its second run out with Mrs Ben. (of course I blame her for breaking it!!)

 

I have replaced the temperature gauge - my back is recovering from the limbo-ing in the footwell whilst routing the capillary tube behind the dash! Whilst the system was partially drained I fitted a NOS sleeved thermostat and the new radiator cap.

 

I was a bit trepid about driving the c.250 mile round trip to the IWE without a temperature gauge but it went like a dream with judicious use of the manual fan.

 

Again very many thanks to all who gave advice on here and at the IWE. Much appreciated!

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