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Thread: GT6 Based overheating

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  1. #1 GT6 Based overheating 
    regular forum contributor Club Member
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    Hello,
    One issue coming after the other, My GT6 based roadster has now successfully passed the french MOT after i rebuilt the carbs
    I then have been able to drive the car from my father's place , close to Calais, to my living place, near Lyon.

    My current concern is that I am facing overhatings:
    2 times, during MOT and during another time I left the engin static, coolant went boiling, hopefully the motor was stopped erly enougfh to avoid major breakdown!

    The cooling system that came with the car config is the following:
    • electric fan activated full time
    • thermostat removed by previous owner
    • radiator estate and model unknown, but no evidence of a bad shape
    • Passenger compartment radiator (heater) installed (and running in hot position full time to help cooling)
    • The cooling circuit includes an expansion tank, and an overflow Bottle (looks strange to me, but i am not an expert
    • original fan on pulley removed (could not enter into the initial place as the electric fan was installed)



    I have a temperature gauge, but suspect that the display part is not fitted with the correct sensor as the pointer does not go over a fourth of the face zone, so I get a temperature estimation thanks to a lowcost chinese thermometer.
    Yesterday run was a 480km trip, outside temperature was arround 20°C. I was not able to drive over 55 mph (90km/h), because the car temp was slightly increasing, and have to stop every 1/2h (car temp going overs (if my chinese temp sensor is accurate) over 100 to 105 °C).


    What I have already done:
    I have purged the coolant, and rinced the radiator and circuit with tap water, and refilled with coolant

    What I plan to do/ suspect:
    • I will change the water pump, I think it is not an element that is ofently damaged, but it cannot be a bad thing to go for a new one
    • I did not identify the points to bleed air from the cooling circuit (I mean the standard ones + I will probably have to add a bleeding tap of . the expansion tank is pretty flat, and installed under the bonnet, so not that higher from the other components of the cooling circuit, compared to the cars I know=> I think my bleed is the main thing to spot in a first time
    • Passenger compartment radiator (heater) circuit looks to me a bit high (radiator seats at the left (UK passenger side ;-)) of the Battery), so a bit high, It would certainly be easyer to bleed with adding a bleed tap on the higher rubber hose.
    • I wonder if, as the thermostat is not there, the coolant is not only partially going into the radiator, a too important part of the coolant passing only through the motor?? any advice?
    • One of the Passenger compartment radiator (heater) hoses (the lower, so the return one I guess) Is made up of 2 rubber hoses, one conected to the radiator, the other one going to the font of the motor.
      the 2 rubber hoses are linked thanks to a steel pipe, which is located betweek the engine block, and the exhaust manifold, as there is no support for the steel pipe, it comes in contact with the exhaust manifod, which is mybe not a good idea.
    • If the bleed does not solve the issue=> radiator expert to rebuild the radiator & motor expert to define if the way the cooling circuit has been assembled does not show big issues


    Thanks for your patience if you took time to read all this, If you have any suggestion, or advice on my way to analyse the issue, it is going to be warmly welcome... I understand hox a standard cooling system works, on a standard car, I know that the manufacturer sollution was correctly designed, but on such a kitcar, I am a bit puzzled!
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  2. #2 Re: GT6 Based overheating 
    frequent forum contributor Club Member kahawi's Avatar
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    You say the ‘thermostat’ removed by previous owner, do you mean the electric fan switch, or the actual engine thermostat?

    If the latter, then you will have big overheating problems. Coolant has to move slowly through the radiator in order to lose heat, with no water-thermostat there will be no restriction and no cooling affect at all. The engine will simply get hotter and hotter, which sounds like the problem you have?

    First step, replace the engine thermostat.
    (2nd Owner of Marlin Hunter, chassis No. 157 (May 1998). Ford-based with 2.3ltr DOHC engine).

    Marlin Hunter R500 ULA
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  3. #3 Re: GT6 Based overheating 
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    Well, yes I am talking about the motor thermostat... that's a good track.
    As the expansion tank is connected to the Thermostat housing, then I will have to check if the way it has been done still allows to put the thermostat.
    Thanks for your feedback!
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  4. #4 Re: GT6 Based overheating 
    frequent forum contributor Club Member b_caswell's Avatar
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    Agree with Kahawi about the thermostat they come in various opening temperatures the normal for the Triumph engine being 88º .

    Can you post a couple of pictures of the engine bay and radiator to help understand your set up.

    As you had to rebuild the carburetors to pass the French MOT the engine may be running too lean/weak mixture which will also
    cause the engine to run hot.
    Ben Caswell probably not the last word on anything here!!
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  5. #5 Re: GT6 Based overheating 
    frequent forum contributor Club Member
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    Hi

    I have a Roadster with a Marina 1800 B series that had a similar problem.

    I have solved this by fitting a 75 deg Thermostat and my electric fan cuts in a bit earlier than ideal at 90 deg.

    The Temperature guage runs at just over a 1/4 on the brand new Smiths Dolomite/ Triumph GT6 gauge that I am using. I swapped the MGB sensor for a Triumph sensor that is fitted in the cylinder head, although the resistance values are different, interestingly at that part of the scale they still read the same.

    The car behaved impeccably in trafffic, even during the very hot summer that we had in the UK last year.
    Heating problem cured

    Here is an example of an equivalent 75 Deg GT6 Thermostat and Gasket:
    https://www.ebay.co.uk/itm/TRIUMPH-H...frcectupt=true
    Last edited by Ye Ol Ripper; 03-04-2019 at 04:12 PM.
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  6. #6 Re: GT6 Based overheating 
    frequent forum contributor Club Member
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    It is probably not the problem but ensure that the flow through the header tank is the correct direction - I have seen cars where the header tank which is intended to remove air from the water system works to ADD air

    And is there some way of changing this bloody awful look that the site has acquired?
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  7. #7 Re: GT6 Based overheating 
    frequent forum contributor Club Member
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    As far as the look of the page goes, go to the bottom left of this page and you will find a box with some choices.
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  8. #8 Re: GT6 Based overheating 
    frequent forum contributor Club Member Tony Stott's Avatar
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    ^ well I'd missed that feature, thanks for the info!! ; -))
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  9. #9 Re: GT6 Based overheating 
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    Default style seems better. Just found it.
    Liz
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  10. #10 Re: GT6 Based overheating 
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    Thanks for all your feedbacks.
    I will try to put some pictures, it can help to understand how it's made, and may also help someone looking for what can the cooling system configurations.
    Here is the global system:

    I will try to update my post as soon as possible with some extra pictures.

    I have dismantled the main coupling spyder (a pure plumbing creation) as there was one or more leaks on the brazes, and will bring it to a plumber for a rebuild and reengineering (There is a reduction from that should, according to me be avoided):



    The modification I plan to make in white here under:






    after purging, I saw that some motor oil (nice black color, no emulsion, max 30ml of oil) was in the purged coolant... Any chance to have a coolant/ oil exchange elsewhere than on the head gasket ?? :-(
    the last purge was made just 1 week and 500km ago...

    I am still waiting for the parts: new coolant pump, thermostat and gasket, to go further in this investigation.
    Last edited by leklek; 08-04-2019 at 01:32 PM.
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