GT6 radiator modification. Still some cooling problems. Is this "normal"?

[RichardS]

My GT6, as purchased last year, was fitted with a blue plastic 8 blade fan and a Kenlowe electric fan but had no cowling of any sort on the back of the rad. The engine also has a high-performance cam fitted by the previous owner so I suspect it is generating a little more heat than standard.

I fitted a lower temp thermostat and an accurate temperature gauge and found that on every trip, even in cool weather, after a few minutes at dual-carriageway speeds it was necessary to turn on the electric fan as the temp gauge only remained at the stable thermostat-controlled temp of about 83 for a few minutes in hot weather and a bit longer in cool weather.

I was sure that the engine fan was not working efficiently as it was well away from the rad and was not being helped by the electric fan when it was not turned on.

I have therefore fired up the MIG and produced the cowling shown in the photos which totally encloses the fan. As soon as I started the engine I could see that something had changed because the electric fan blades started spinning as a result of the airflow. The electric fan did not do this before I fitted the cowling so I was feeling positive and went for a drive with the electric fan still in place. This was yesterday and today so high 20's around here.

Things were better and as long as the car was travelling at 60 or 70 the temperature held at 83 but once I turned off the dual carriageway the temperature started to creep up and turning the Kenlowe on brought it back down which suggests that the system was at its limit.

I removed the Kenlowe and tried again today. The results are much better in that during the entire run the temp was stable at 83. However, I did not meet any traffic jams so was never stationary so when I arrived home I just let the engine idle to see what happens. Sure enough, after about 5 minutes the temp started to creep up again and reached 90 after 10 minutes before I switched it off.

I was hoping that it would hold a steady 83 at idle even after a good run in hot weather but it seems not to be. Any advice about whether I am striving for the impossible would be helpful, along with any further ideas.

Thanks

Richard

[Clive]

I think you are aiming for an unrealistic target.

The cars have no issues with 90degrees plus, they won't boil until about 120. 

I would point out you are missing the cowling at the front of the rad, which would help when moving, but not when stationary.

Is the rad definitely clean/clear? 

[Pete Lewis]

do you have the cowl/duct  in font of the radiator  and the number plate is not covering the front grille 

has the rad been flushed or maybe a flow test??

does the heater work , as blocked bypass tubes etc can help with hot 

pete

[cliff.b]

I thought a typical running temperature was in the region of 90/95C

[Pete Lewis]

not if the stat is 82c (std) and the rad does its work it should cool the water and let it into the block when the stat opens/modulates the flow 

i the rad core is partial blocked then you build up higher and higher as there is limitations to what you are cooling 

Pete

[cliff.b]

2 hours ago, Pete Lewis said:

not if the stat is 82c (std) and the rad does its work it should cool the water and let it into the block when the stat opens/modulates the flow 

i the rad core is partial blocked then you build up higher and higher as there is limitations to what you are cooling 

Pete

Pete, just to clarify my understanding, am I correct in thinking the thermostat temp quoted is when it starts to open and it won't be fully open until it gets maybe 10 Deg hotter?

[johny]

I thought the stat starts to open at its marked value and wont be fully open until maybe 8º higher. Then I think in theory once fully open the temperature should never go above that and the thermostat opens and closes depending on the temperature. However my Triumph experience is that the temperature goes higher and reaches an equilibrium which depends on the rate of heat removal from the radiator (determined by the difference in rad surface/air temperature plus cooling air flow).

Fans electric or mechanical normally make no difference to cooling on the move as the air flow should be much greater than any fan can produce. If the temperature goes too high while travelling the problem is either too much heat being produced by the engine or restricted air flow or restricted heat transfer or a combination of these factors.

The things to look at are: engine adjustments (weak mixture either from setting or leaks, over advanced timing); airflow restrictions from number plates, ducting, additional cooling fans, damaged radiator fins; water circuit cleanliness and water pump effectiveness.

Once this aspect of cooling has been resolved then stationary cooling can be addressed if still a problem...

[Nigel Clark]

Hi Richard,

When I first got my GT6 about 20 years ago, it struggled with cooling. After trying electric fans, in front and behind the radiator, I concluded they made matters worse by obstructing air flow.

I built a similar cowl to yours, from alloy sheet pop riveted together. It transformed cooling with only the standard crank driven fan.

The engine now normally runs at about 40% deflection on the standard temp gauge, rising to 60-70% gauge deflection in traffic. Pointing a digital IR temp thingy at the thermostat housing gives readings of 75-85 Centigrade when really hot.

More important, nothing bad has happened, the engine has run happily like this for many years and thousands of miles.

Hope this is some help and reassurance!

Nigel

[RichardS]

4 hours ago, Pete Lewis said:

not if the stat is 82c (std) and the rad does its work it should cool the water and let it into the block when the stat opens/modulates the flow 

i the rad core is partial blocked then you build up higher and higher as there is limitations to what you are cooling 

Pete

Thanks to all for the helpful comments.

When I got the car it had no thermostat fitted and a lot of blockages in the cooling system. I fitted the lower temp option thermostat which I think was 75 degree and have drained and back-flushed the system several times. I dug out some total blockages with long pieces of stiff wire! All the passages now seem to be clear and water pours out of every spigot and the block drain. When I fully drained it yesterday there was no crud at all but I still flushed through with the hose pipe so I'm confident that the system is clear.

I do not have any cowling in front of the radiator. Perhaps that was removed to fit the electric fan? As has been pointed out, a front cowling would probably only affect cooling whilst moving but if anyone has a photo of what I'm missing I would be very interested.

With a 75 degree thermostat, I would expect the gauge to stabilise in the lowish 80's if the system if the cooling is able to keep pace with heat being generated and, sure enough, that seems to happen now as long as the car is moving. I suppose that I'm used to modern cars which run at the same mid-range temp under every condition. I have a V8 Jaguar which only has electric fans and you can leave it all day at idle and the fans will never even start as the capacity of the massive radiator is able to dissipate all the heat being produced by the engine without any forced airflow. The GT6 is clearly a very long way from that level of cooling performance but I was hoping that my ducting would maintain the lowish-80's equilibrium position.

The number plate is partly covering the air intake but, as with the front cowling, that's presumably not affecting the stationary situation?

I can see that I will need to do some more testing. I didn't try it today but I suspect that if I had turned on the heater and possibly the blower the extra cooling might well have pulled it back down although in today's weather that would not be a pleasant experience. I used to have a 1960's Vauxhall Victor and that used to overheat in the summer so I disconnected the air duct pipes so it would blow hot air into the engine bay and that always kept the temp within the normal range. However, that's not an option with the Triumph because the matrix and blower are in the cabin rather than in the engine bay.

I'll report back when I've done some more testing on a longer run.

Thanks to all

Richard

[JohnD]

Are you sure you had a "Kenlowe"   They normally come with their own cowling, that doubles as the bracket to hold it in place, close to the rad, with fasteners through the matrix!

[Clive]

7 hours ago, RichardS said:

Thanks to all for the helpful comments.

When I got the car it had no thermostat fitted and a lot of blockages in the cooling system. I fitted the lower temp option thermostat which I think was 75 degree and have drained and back-flushed the system several times. I dug out some total blockages with long pieces of stiff wire! All the passages now seem to be clear and water pours out of every spigot and the block drain. When I fully drained it yesterday there was no crud at all but I still flushed through with the hose pipe so I'm confident that the system is clear.

I do not have any cowling in front of the radiator. Perhaps that was removed to fit the electric fan? As has been pointed out, a front cowling would probably only affect cooling whilst moving but if anyone has a photo of what I'm missing I would be very interested.

With a 75 degree thermostat, I would expect the gauge to stabilise in the lowish 80's if the system if the cooling is able to keep pace with heat being generated and, sure enough, that seems to happen now as long as the car is moving. I suppose that I'm used to modern cars which run at the same mid-range temp under every condition. I have a V8 Jaguar which only has electric fans and you can leave it all day at idle and the fans will never even start as the capacity of the massive radiator is able to dissipate all the heat being produced by the engine without any forced airflow. The GT6 is clearly a very long way from that level of cooling performance but I was hoping that my ducting would maintain the lowish-80's equilibrium position.

The number plate is partly covering the air intake but, as with the front cowling, that's presumably not affecting the stationary situation?

I can see that I will need to do some more testing. I didn't try it today but I suspect that if I had turned on the heater and possibly the blower the extra cooling might well have pulled it back down although in today's weather that would not be a pleasant experience. I used to have a 1960's Vauxhall Victor and that used to overheat in the summer so I disconnected the air duct pipes so it would blow hot air into the engine bay and that always kept the temp within the normal range. However, that's not an option with the Triumph because the matrix and blower are in the cabin rather than in the engine bay.

I'll report back when I've done some more testing on a longer run.

Thanks to all

Richard

The cowl fits in front of the rad, and was a factory fitment.

I have a slight worry that the radiator itself may have a few tube blocked. Once blocked, they are impossible to clear by flushing (water just flows through the clear tubes instead) but you lose cooling capacity. Old skool radiator repairers could open the rad up and poke all the tubes through to clear them, which is the only alternative to a recore. In fact, a rad place should be able to check if the rad has blockages. May be worth having it checked over if you can find somewhere.

BUT I do wonder if you are expecting too much.  You simply cannot compare to anything vaguely modern. They cheat, the temp gauge is controlled by the ecu and gives a nice steady reading for a wide range of temps to stop people worrying. The little honda I am driving has a 2 colour led light, either cold or hot, goes off when temp is OK. Which is fine by me. 

[Dick Twitchen]

7 hours ago, RichardS said:

I do not have any cowling in front of the radiator. Perhaps that was removed to fit the electric fan? As has been pointed out, a front cowling would probably only affect cooling whilst moving but if anyone has a photo of what I'm missing I would be very interested.

Given the nature of the mechanical fan it pulls air through the rad and the electric fan & shroud in the photos plus the number plate are effectively blocking that.  I have a shroud in front of the rad and just a mechanical fan and with the system flushed have coped with trips to Classic Le Mans and the attendant queuing in temperatures higher than recently.

Dick 

https://www.jamespaddock.co.uk/radiator-cowl-ss-black-gt6-2

[Pete Lewis]

to test radiator flow for warranty claims we made a known sized header tank  about 10 gallons  at a 15ft head  and timed the discharge seconds compared to a new unit using a garden hose has little effect on have you got a series of blocked tubes 

i think the fact the stat  had been removed and much crud in the system does point to your radiator needs a serious look 

or without the basics working you will be chasing your tail for ever and pouring £££ down the drain

for flushing  i always recommend cheap washing soda it really works  but no product will clear blocked tubes thats as clive says  a mechanical prod out or best is just get it re cored   and you are starting the race with  good horse not chasing the old nag 

Pete

[johny]

It would be a dream come true if just changing the thermostat lowers the running temperature of the system😍 Unfortunately as I say all it means is that it opens earlier, goes to fully open and the temperature continues to rise until it reaches exactly the same equilibrium point as with the original thermostat!

In my experience nothing improves cooling like a recored radiator especially of course if done with a modern 1cm tube spacing (original was 1/2") and the vertically installed wavey type fins... 

[Ian Foster]

Richard

I run my Mk2 with just a 12" Spal sucker fan. I have engine bay side valances and front cowl on which I have extended the sides to the limit of what the bonnet structure will allow.

My radiator has been re-cored with the 'biggest' modern core the radiator specialist could find. The fan is switched by a sensor fitted into the top tank and comes on when the gauge reads just above half and switches off when just below half. I have a manual override switch which I use if I anticipate a lengthy stop or don't want to arrive at my destination with the fan on (not cool!?!). At idle the fan will just cycle on and off as controlled by the sensor.

Some will say that the original fixed fan and shrouding 'as Triumph intended' will be adequate, but as you have suggested there are some factors that might make your/our cars run hotter than back in the day, ie unleaded and now ethanol modified fuel and performance modifications (cams and raised CRs). If you look at the design of the GT6 pipework, Triumph were obviously struggling to get enough coolant flow to the radiator or they wouldn't have added the additional pipe from the thermostat housing to the filler neck. No other Triumph model has this.

In terms of your set up, I would agree that the electric fan in front of the radiator is probably not helping, as it is just providing a restriction to the airflow. I would definitely add a front shroud and make it as efficient as possible by extending the sides as much as the local architecture on your Mk3 allows. Your shroud around the fixed fan is a good idea and should really be beneficial in pulling air through the radiator core, but I think it could be finessed by extending it to fully cover the core. There will be guidance online as to the ideal form or shrouds, with recommendations on clearance to the fan blades etc. 

I have attached a pic of my set up, which works pretty well. Hope this helps.

Ian

 

[RichardS]

11 hours ago, JohnD said:

Are you sure you had a "Kenlowe"   They normally come with their own cowling, that doubles as the bracket to hold it in place, close to the rad, with fasteners through the matrix!

Yes, the Kenlowe does have its own casing/cowling but I've removed the electric fan so the cowling has now gone.

Richard

[RichardS]

3 hours ago, Dick Twitchen said:

Given the nature of the mechanical fan it pulls air through the rad and the electric fan & shroud in the photos plus the number plate are effectively blocking that.  I have a shroud in front of the rad and just a mechanical fan and with the system flushed have coped with trips to Classic Le Mans and the attendant queuing in temperatures higher than recently.

Dick 

https://www.jamespaddock.co.uk/radiator-cowl-ss-black-gt6-2

Thanks to those who have provided details of the forward cowling.

I will be able to fabricate something similar and possibly even more extended with the sheet I have left over from the fan cowling.

I realise that it's more of a forward movement thing but, thinking about it, if the car arrives at a traffic jam with a lower temperature of coolant then it should provide a bit more headroom for the time at idle in the jam.

Richard

[RichardS]

3 hours ago, Pete Lewis said:

to test radiator flow for warranty claims we made a known sized header tank  about 10 gallons  at a 15ft head  and timed the discharge seconds compared to a new unit using a garden hose has little effect on have you got a series of blocked tubes 

i think the fact the stat  had been removed and much crud in the system does point to your radiator needs a serious look 

or without the basics working you will be chasing your tail for ever and pouring £££ down the drain

for flushing  i always recommend cheap washing soda it really works  but no product will clear blocked tubes thats as clive says  a mechanical prod out or best is just get it re cored   and you are starting the race with  good horse not chasing the old nag 

Pete

The rad appears to be fairly new and appears to be getting hot across its entire surface. Unfortunately, unlike most other rads I've worked on, the top of the matrix is not really visible. I've seen rads in the past where you can actually see that some tubes are blocked. It might be the case that the rad itself needs to be overhauled but, to be honest, the only costs so far are my time and I don't mind that but if these cost-free mods don't do the trick then I'll remove the rad again. 

I could try pouring diluted hydrochloric acid into the inverted rad as that's something that seemed to make an improvement when I tried it in the 1970's but it's not without it's implications and might still not clear blocked tubes.

Richard

[RichardS]

3 hours ago, johny said:

It would be a dream come true if just changing the thermostat lowers the running temperature of the system😍 Unfortunately as I say all it means is that it opens earlier, goes to fully open and the temperature continues to rise until it reaches exactly the same equilibrium point as with the original thermostat!

In my experience nothing improves cooling like a recored radiator especially of course if done with a modern 1cm tube spacing (original was 1/2") and the vertically installed wavey type fins... 

Yes, I agree that people who remove the thermostat in order to cure an overheating problem are failing to understand the physics involved. However, where there is no thermostat fitted at all, one might as well fit the cooler range variant.

The radiator does appear to have rather "coarse" horizontal fins rather than the the finer vertical ones that I'm more used to seeing.

Is it possible to have the existing rad re-cored with the finer fins etc or is it cheaper to just buy a new rad built to a better design if such a thing is even available?

Richard

[RichardS]

2 hours ago, Ian Foster said:

Richard

I run my Mk2 with just a 12" Spal sucker fan. I have engine bay side valances and front cowl on which I have extended the sides to the limit of what the bonnet structure will allow.

My radiator has been re-cored with the 'biggest' modern core the radiator specialist could find. The fan is switched by a sensor fitted into the top tank and comes on when the gauge reads just above half and switches off when just below half. I have a manual override switch which I use if I anticipate a lengthy stop or don't want to arrive at my destination with the fan on (not cool!?!). At idle the fan will just cycle on and off as controlled by the sensor.

Some will say that the original fixed fan and shrouding 'as Triumph intended' will be adequate, but as you have suggested there are some factors that might make your/our cars run hotter than back in the day, ie unleaded and now ethanol modified fuel and performance modifications (cams and raised CRs). If you look at the design of the GT6 pipework, Triumph were obviously struggling to get enough coolant flow to the radiator or they wouldn't have added the additional pipe from the thermostat housing to the filler neck. No other Triumph model has this.

In terms of your set up, I would agree that the electric fan in front of the radiator is probably not helping, as it is just providing a restriction to the airflow. I would definitely add a front shroud and make it as efficient as possible by extending the sides as much as the local architecture on your Mk3 allows. Your shroud around the fixed fan is a good idea and should really be beneficial in pulling air through the radiator core, but I think it could be finessed by extending it to fully cover the core. There will be guidance online as to the ideal form or shrouds, with recommendations on clearance to the fan blades etc. 

I have attached a pic of my set up, which works pretty well. Hope this helps.

Ian

 

Thanks Ian.

I wondered why the rad has two inlet tubes as I've never seen anything like that. If it is simply to get more flow into the rad then I agree with you that it suggests an element of desperation by the Triumph engineers.

I will knock up a front cowling as you and others have suggested.

The problem with the rear cowling is that the crankshaft axis is not actually in the centre of the rad but set over to the nearside. I don't understand why this is the case but it does mean that there is some "wasted" matrix on the offside. The limiting factor for a simple circular cowling design is the clearance to the water pump boss. I measured it all very carefully and have ended up with a clearance of about 3mm to the inner section boss. To cover the wasted matrix and still avoid the water pump would require a considerably more complicated fabrication.

Richard

[johny]

I believe its possible to recore with tubes closer together (so theres more of them) and the denser fins but this has to be carefully verified with the company involved beforehand. Theres different 'uprated' ones on ebay with, for example, a 5th row of tubes but as I say you have to be careful because that can just mean the spacing is offset and you still have the same overall number of tubes.

Aluminium units are also available but are usually very expensive and not necessary...

[WWT338J]

The GT6 radiator has two inlet pipes to assist with purging air, I think. That's also one reason why the heaters never work well (although lack of cabin heat is not often an issue in the GT6). 

Another factor to consider is the water pump, particularly at slow engine speeds. The radiator can only dissipate heat from the water that is flowing through it.

David 

[johny]

There are improved impellers available but I always keep in mind that the same standard pump is used all the way up to the 150hp TR6...

[DanMi]

I would suggest that the electric fan or something else is blocking the airflow through the radiator, as at speed the airflow from the forward movement should be sufficient and no fan should be needed. If it was a blocked rad then turning the electric fan on at speed would have little effect, so the problem would seem to be airflow, of course cowls in front of the rad would help.

[DanMi]

just read that you have tried removing the electric fan. I should read more thoroughly.