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TR Paul

Thermostat Substitute?

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Hi Chaps... In the current spell of (un)seasonal weather, TRoy, my 1970 TR6 pi has been running rather warm. The cooling system seems healthy enough, as in 'normal' weather, he runs at just over the 'N' mark on the temp gauge, but at this time, he's hovering at half way between 'N' and 'H', moving up to three quarters of the way in traffic. This is after fitting a 74degree thermostat, so I was thinking about trying to bring the temperature down a bit further.

I gather it's unwise to go too far without a thermostat ,as this can cause uneven distribution of the water around the head & block. So I was considering either a blanking sleeve (as used in race spec BMC 'A' series engines), as this will (in an 'A' series at least; perhaps the TR engine is different in this respect?) make the engine run cooler, without disturbing the distribution, or the 'skeleton' of an old thermostat:- a thermostat with the moving component (the wax bit & spring) removed, which, in theory should have the same effect as the blanking sleeve?

Has anybody tried anything like this? Is this worth a try, or am I just wasting my time, or maybe even asking for more trouble?

Should I just persevere with these temperatures, 'til the weather returns to 'normal'; after all, TRoy hasn't actually overheated, in some fairly extreme conditions recently.

As ever, your advice & opinions will be much appreciated,

Cheers,

Paul.

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High 20s should not really make it run hot.

Are you sure it is reading correctly?

 

How old is your radiator is probably the first question assuming the car is running right? (which makes timing, leanness and blown head gasket unlikely)

 

Is it the correct core in the rad - some got rebuilt with a core with fewer rows in them.

Have you got an electric fan, and if so is it blowing/sucking front to back?

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With hoter water the radiator gets much more powerful.

For me it sounds everything is ok with your baby,

I would do nothing at all.

 

Just one question: your thermostat is a wax thermostat?

On a friends TR6 we found a bellows

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Main problem is that we are not used anymore about the fact that the arrow of the temperature gauge moves,

because on our modern cars the producers fixed it to show always the same temperature to prevent senseless complaints from us costumer.

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With hoter water the radiator gets much more powerful.

For me it sounds everything is ok with your baby,

I would do nothing at all.

 

Just one question: your thermostat is a wax thermostat?

On a friends TR6 we found a bellows

+1

Hi Paul,

if you do not have an electric fan then think about one. They give excellent cooling when needed - never normally n the move.

 

Easier to install than any fancy thermostat etc.

 

However if your needle does not hit the Red and you do not boil over in TRaffic then why bother at all.

 

Roger

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Hi Paul,

 

I am on the South coast also and have an electric pusher fan (not the largest I have seen & the orig removed) with thermostat switch in the radiator return pipe, it's not overheated, the temp gauge is about normal in this hot weather but I did notice that the underbonnet temps are very high and the metal fuel pipes hot to the touch.

I certainly would not mess with the thermostat, it would appear as though your gauge is correct along with your thermostat, so its the usual stuff, is radiator shroud installed, clear radiator etc. As suggested electric fan is a good idea in my opinion although it may mask an underlying inefficiency elsewhere, if you do have an electric fan then you probably do have an issue that needs further investigation.

As also mentioned is it really an issue other than peace of mind, lots of modern cars don,t even have a temp gauge.

 

Regards,

 

John

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Forget the blanking sleeve idea. That’s for engines, like the A series, with a bypass hose. There’s no bypass on the 6 cylinder engine. Personally if your temperature gauge behaves as you describe I wouldn’t worry.

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High 20s should not really make it run hot.

Are you sure it is reading correctly?

 

How old is your radiator is probably the first question assuming the car is running right? (which makes timing, leanness and blown head gasket unlikely)

 

Is it the correct core in the rad - some got rebuilt with a core with fewer rows in them.

Have you got an electric fan, and if so is it blowing/sucking front to back?

All as above is correct but there is another issue which is the sender unit in the thermostat housing. My gauge started to read low so I bought another from Moss that one then put the needle past the normal mark? After investigation this sender unit had a Lucas part no. on? This part number turned out to be the wrong part! Moss did not have the correct Lucas part no. and had never ever ordered that one. So by chance I phoned Caerbont Automotive Instruments as they re-manufacture many Smiths parts TT4803-00A refers and is the OEM part so I ordered that and my needle is back in the middle again! By the way they also manufacture the OEM speedo gear box Part number BG2401-05 which has caused so much aggro on this Forum.

 

Bruce.

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That is a known issue Bruce and has been discussed several times in old threads here. There are a variety of different senders and getting the right one for your particular system is imperative.

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Hi Rob,

I plan to test the entire circuit (sender, stabilizor, gauge, wiring) with the sender connected and hanging in a pan with water, then raise the water temperature and measure temp and gauge reading.

Off course connected to 12V battery.

Does this make sense?

Thanks,

Waldi

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That is a known issue Bruce and has been discussed several times in old threads here. There are a variety of different senders and getting the right one for your particular system is imperative.

Hi Rob! Thanks for that bit of info which I have missed out on. But if you go direct to Caerbont you can get the correct part without the aggro and figure in the air, is it going to work and how long for?

 

Bruce.

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Hi,

 

I guess there are indeed some TR6 drivers

thinking that they are lucky to have no bypass on the cooling circut.

But sorry me, there is on at the TR6 engine,

as it is urgently needed on all "petrol heated" engines.

It's a 8 mm drill in diameter in the waterpump housing itself.

But there this is no reason to worry that at all.

 

Ciao Marco

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Yes that is the correct way to do it Waldi.

Thanks Rob!

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Hi, thanks for all the replies to my post; some interesting points raised. The radiator was re-cored in 2013, & I do have a Kenlowe fan (fitted by a p.o). It's mounted on the front (grill side) of the rad, so you'd say it blows the air, rather than sucks. As for the gauge sensor, yes, I've had issues with these in the past. I've heard (Possibly on this forum or in 'TRaction') that the ones with black plastic are more accurate than the red ones. Oh, and my thermostat is a wax item; the only time I've encountered a bellows one, was on the Rover (P4) 100 I used to run 15-20 years ago.

Cheers,

Paul.

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Hi Rob,

I plan to test the entire circuit (sender, stabilizor, gauge, wiring) with the sender connected and hanging in a pan with water, then raise the water temperature and measure temp and gauge reading.

Off course connected to 12V battery.

Does this make sense?

Thanks,

Waldi

 

 

I tested the entire loop yesterday.

Put a charger on the battery while the car is not running to achieve 13.5 to 14 V , since the regulator should have an output of 10V, and 12.5V is relatively close.

Connected sender to wire and made an earth to the sender body.

Put sender in water cooker ...yes, she was home.

Tested at 50, 80 and 95 degrees C and marked on the glass of the gage.

I have a new and my old sender and tested both.

The old sender was in the middle of the gage at 80C and close to red at 95C.

The new sender was 4/5 mm more to the right, so indicating a higher temperature than the old one.

Based on this I´ve decided I will re/use the old sender, and now know what temperature belongs to the gage scale.

What I learnt from this is that the reading on the gage is just a rough indication, but actual measurement of the coolant temperature when in doubt, is needed.

 

Waldi

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Hi Waldi,

Very interesting findings you've made with your experiment. Not being an expert on these things, I'd say that if an accurate temperature reading is required, a capillary gauge would be the way to go; As long as they are consistent, the TR6 style electrical unit, as you've discovered, should be adequate.

As regards 'TRoy', In the current spell of slightly cooler (but more pleasant) weather (compared with 2-3 weeks ago), the needle is now hovering much closer to the middle of the temp gauge.

Again, many thanks for all your advice & comments,

Best wishes

Paul.

Edited by TR Paul

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Thanks Paul,

Glad to share.

Waldi

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I had the opposite problem a few weeks ago - gauge showing a running temperature down near the first mark on the gauge. The change from reading Normal to reading Low happened in a very short period of time, pretty much a step change in performance. After a bit of checking, including the use of an IR 'temp gun', I found that all was OK with everything except the sensor.

Doing a series of resistance/temperature measurements revealed the defective sensor was good for up to around 65degC, but then exhibited almost no resistance change for higher temperatures.

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Putting a lower operating level thermostat is not the answer. It will just start opening at a lower level and then the water temperature will just creep up further if there is insufficient cooling....assuming the reading from your gauge is trustworthy?

 

I run an 82degC with a Kenlowe (blower) and I have mine set up to provide a fairly stable temperature. Excessive hysteresis on the fan temperature controller may prevent some people form achieving this though.

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