TR4a Commissioning Thread

[Z320]

Hi Peter,

thank you to point on me 😄, I better will not post my opinion about "bleeding" the system.

I just fill the rad up with coolant, drive it and finally check it, no special treatment, no worry or special doing at all.

IMO with Steven's everything should be OK, as I understand the cool lower hose was determined at the garage (where else).

With the car on idle the top hose gets hot "relatively" fast, while the flow through the rad is very low

and the engine looses much heat by its surface and to the long time "cold" oil.

I would disconnect the thermostat from the cables and check it with a multimeter.

The best position to install it? I don't know, as you might know I drive with a BMW 1602 fan.

The blow out of coolant to the overflow bottle very likely is an issue of overfilling --> I suppose this is why Triumph fiited it.

I drive with the rad core only about 1 mm covered and the overflow bottle always empty.

Ciao, Marco

Edited May 4, 2025 by Z320
because of my poor English writing

[BlueTR3A-5EKT]

2 hours ago, Z320 said:

Hi Peter,

thank you to point on me 😄, I better will not post my opinion about "bleeding" the system.

I just fill the rad up with coolant, drive it and finally check it, no sepcial treatment, worry or doing at all.

IMO with Steven's everything should be OK, as I understand the cool lower hose was determined at the garage (how else).

The car on idle the top hose gets hot "relatively" fast, while the flow is through the rad is very low

and the engine looses much heat by its surface and to the long time "cold" oil.

I would disconect the thermostat from the cables and check it with a multimeter.

The best position to install it? I don't know, als you might know I drive with a sold BMW 1602 fan.

The blow out of coolant to the overflow bottle very likely is an issue of overfilling --> I suppose this is why Triumph fiited it.

I drive with the rad core only about 1 mm covered and the overflow bottle always empty.

Ciao, Marco

Precisely my understanding of your approach Marco.   I respect and acknowledge it.

[Steven Whitaker]

I’m a bit stuck now.  So, is it ok to let the engine run when the temperature is in the red?  I assume not.  But how do I continue if I cannot run it to tune it to drive it?.  If the bottom hose is cool I assume that means the circulation is poor so the fan won’t really help?

[Z320]

Hi Steven,

your rad cap pretty sure blows coolant off because you overfilled the rad.

In my opionon NO classic car with a classic vertical radiator (until about 1985) needs a overflow bottle.

Let enough air in the system, the pump holds it in the flow and the rad and engine have no problem with it.

The issue with the high temperature could be a original gauge supplied with full battery voltage "12 V".

It need only "10 V" via a voltage regulator in the foodwell, if connected to "12 V" it indicates a too high temperature.

The sensor in the thermostat housing is directly inline with the gauge, unplug the cable and measure the voltage there.

It must not be 12 V but "fast" pulsing 0 V / 12 V / 0 V..... In the foodwell you should hear the stabilsator clicking, if original.

Original it is only a coil heated bimetal switch that simulates 10V by switching 12 V on/off.

The original gauge therefore is heated by the switched voltage, the sensor is a resitance to groung.

Ciao, Marco

(comment: with "12 V" I meen the battery voltage, which is indeed some more than 12 V)

 

[stuart]

25 minutes ago, Z320 said:

Hi Steven,

your rad cap pretty sure blows coolant off because you overfilled the rad.

In my opionon NO classic car with a classic vertical radiator (until about 1985) needs a overflow bottle.

Let enough air in the system, the pump holds it in the flow and the rad and engine have no problem with it.

The issue with the high temperature could be a original gauge supplied with full battery voltage "12 V".

It need only "10 V" via a voltage regulator in the foodwell, if connected to "12 V" it indicates a too high temperature.

The sensor in the thermostat housing is directly inline with the gauge, unplug the cable and measure the voltage there.

It must not be 12 V but "fast" pulsing 0 V / 12 V / 0 V..... In the foodwell you should hear the stabilsator clicking, if original.

Original it is only a coil heated bimetal switch that simulates 10V by switching 12 V on/off.

The original gauge therefore is heated by the switched voltage, the sensor is a resitance to groung.

Ciao, Marco

(comment: with "12 V" I meen the battery voltage, which is indeed some more than 12 V)

 

Wrong sender won’t help with accuracy too. It’s also possible OP has an air lock.

Stuart

Edited May 6, 2025 by stuart

[Steven Whitaker]

14 hours ago, Z320 said:

Hi Steven,

your rad cap pretty sure blows coolant off because you overfilled the rad.

In my opionon NO classic car with a classic vertical radiator (until about 1985) needs a overflow bottle.

Let enough air in the system, the pump holds it in the flow and the rad and engine have no problem with it.

The issue with the high temperature could be a original gauge supplied with full battery voltage "12 V".

It need only "10 V" via a voltage regulator in the foodwell, if connected to "12 V" it indicates a too high temperature.

The sensor in the thermostat housing is directly inline with the gauge, unplug the cable and measure the voltage there.

It must not be 12 V but "fast" pulsing 0 V / 12 V / 0 V..... In the foodwell you should hear the stabilsator clicking, if original.

Original it is only a coil heated bimetal switch that simulates 10V by switching 12 V on/off.

The original gauge therefore is heated by the switched voltage, the sensor is a resitance to groung.

Ciao, Marco

(comment: with "12 V" I meen the battery voltage, which is indeed some more than 12 V)

 

Hi Marco,

Thanks for your comments.  I have a new voltage regulator in the footwell.

I ran the car again last night.  It warmed up to about 75% on the temperature gauge and stabilised.  The top and bottom hoses warmed up and the fan started and stayed on.  No fluid was sent to the over flow bottle and the hose did not blow off.  This is with the 7 lbs radiator cap.  So it seems like maybe there was an airlock somewhere, which settled out over night.  So it seems like all is well.  I took the car for a very short drive (the first since full rebuild) and whilst it felt very warm in the cabin, it didn't 'boil over' or blow any hoses off.  After the very short test drive I switched the ignition off and the fan 'ran on' for a few minutes then switched itself off.

I'll do another test run tonight and report back, but it seems, fingers crossed, that I may be 'over this hurdle'.

Felt good to get the car finally on the public road after 3+ years on the project.  First drive since full nut and bolt restoration.  My heart was in my mouth!

Still lots to do on the car but I feel like I'm 'getting there' now.

It felt very high geared though, even without the over-drive.  Were the diffs a different ratio in Canada compared to the UK cars?

Thanks,

Steven.

 

 

 

[stuart]

30 minutes ago, Steven Whitaker said:

 It felt very high geared though, even without the over-drive.  Were the diffs a different ratio in Canada compared to the UK cars?

Thanks,

Steven.

 

 

 

 

 

 

Only ratios normally fitted would be 3.7 or 4.1 but its possible that a TR5/6 diff has been fitted which is 3.45.

Stuart.

[Z320]

Hi Steven,

great to gear you are pleased with the self restored car.

About the diff ratio: perhaps you can tell the forum members some cominaltion of mph / revs.

If possible in a different thread.

Ciao, Marco

[Steven Whitaker]

29 minutes ago, stuart said:

Only ratios normally fitted would be 3.7 or 4.1 but its possible that a TR5/6 diff has been fitted which is 3.45.

Stuart.

OK, thanks.  Is there a way to tell what I have?

[Steven Whitaker]

16 minutes ago, Z320 said:

Hi Steven,

great to gear you are pleased with the self restored car.

About the diff ratio: perhaps you can tell the forum members some cominaltion of mph / revs.

If possible in a different thread.

Ciao, Marco

OK, thanks.  I will but I did not go more than 20mph yet, ha ha.  Thanks again.

[rcreweread]

14 minutes ago, Steven Whitaker said:

OK, thanks.  Is there a way to tell what I have?

Steven - make sure gearbox is in neutral, jack up one rear wheel high enough so you can see the propshaft flange going into the diff and put a white chalk mark on the flange/UJ making sure the other is firmly on the ground so can’t turn

Chalk the wheel/drum and turn it two full revolutions , counting how many times the prop flange turns - if it goes around about 4 times, it will be a 4.1 ratio , about three and three quarters, it will be a 3.7 and if three and a half, then it’s a 3.45 ratio

Correct/standard TR 4/4A is a 3.7 ratio. With 4.1 being an option and as Stuart says, 3.45 is uk TR5/6! - US 6 cylinder TRs had 3,7 ratios as standard, whereas UK cars were 3.45

if you car is fitted with a late TR6/Dolly Sprint/ Stag box, they do have a long 1st gear compared to earlier boxes

Hope this helps

cheers Rich C-R

[Z320]

41 minutes ago, Steven Whitaker said:

OK, thanks.  I will but I did not go more than 20mph yet, ha ha.  Thanks again.

I considered to determine some data for you,

but not faster than 130 km/h, to safe you from trouble

[Steven Whitaker]

On 5/7/2025 at 2:22 PM, rcreweread said:

Steven - make sure gearbox is in neutral, jack up one rear wheel high enough so you can see the propshaft flange going into the diff and put a white chalk mark on the flange/UJ making sure the other is firmly on the ground so can’t turn

Chalk the wheel/drum and turn it two full revolutions , counting how many times the prop flange turns - if it goes around about 4 times, it will be a 4.1 ratio , about three and three quarters, it will be a 3.7 and if three and a half, then it’s a 3.45 ratio

Correct/standard TR 4/4A is a 3.7 ratio. With 4.1 being an option and as Stuart says, 3.45 is uk TR5/6! - US 6 cylinder TRs had 3,7 ratios as standard, whereas UK cars were 3.45

if you car is fitted with a late TR6/Dolly Sprint/ Stag box, they do have a long 1st gear compared to earlier boxes

Hope this helps

cheers Rich C-R

Thanks for the advice.  I'll do this and report back. 

Cheers.

[Z320]

3,050 - 3,100 revs for 80 miles per hour (128 km/h) yesterday,

on my 5 th gear, this a minimal longer that 4 th + overdrive

[Steven Whitaker]

On 5/11/2025 at 12:46 PM, Z320 said:

3,050 - 3,100 revs for 80 miles per hour (128 km/h) yesterday,

on my 5 th gear, this a minimal longer that 4 th + overdrive

Thanks.  I won’t be doing 80mph, ever!  And I need to run it in too!

[Z320]

😁

Edited May 15, 2025 by Z320

[Steven Whitaker]

Hi All.  I’m back at it, after a 15m break due to life….  So the car is running now, but the fan is stuck on.  I think the in line Revotec temperature sensor is faulty.  Can anyone recommend a quality replacement please?

Car is going for a carb and ignition set up in the next week or so.

Thanks, Steven

Edited August 17 by Steven Whitaker

[RogerH]

Hi Steve,

I may not be much help on this one. But, why do members go for the Revotec rad fan. There seems to be so much grief with them.

There are many quallity fan manufacturers on the market (Spal fir instance) (and many good scrap yards) and cobbling a system together is so simple.

Fan, Thermostat in the pump down pipe, over ride switch and a bit of wire - Bobs your Uncle (or possibly your Aunty in these strange times)

Consider a rebuild

Roger

 

[Steven Whitaker]

36 minutes ago, RogerH said:

Hi Steve,

I may not be much help on this one. But, why do members go for the Revotec rad fan. There seems to be so much grief with them.

There are many quallity fan manufacturers on the market (Spal fir instance) (and many good scrap yards) and cobbling a system together is so simple.

Fan, Thermostat in the pump down pipe, over ride switch and a bit of wire - Bobs your Uncle (or possibly your Aunty in these strange times)

Consider a rebuild

Roger

 

Hi Roger.  The fan is great.  It’s the sensor that plays up apparently.  Just need a fresh sensor so saw folks mention the otter.  Looking for a link please.  Cheers.

[Firefly]

    Roger the Cobbler,

                               I hesitate to say this (fingers and everything crossed), I have had a Revotec controller for 7 year and ok so far. I chose this because it has an adjustable set point, and not knowing how my cobbled together GT6 engine in an MGB was going to perform temperature wise led me that way. I agree the type you suggest is probably is ultimately more reliable.  Another can of worms, is it better to have the controller in the out from the engine or inlet. Answers on a post card please.    Mac (cobbler)  

[Steven Whitaker]

And in addition to my request for a link, what temps should the fan come on and off please?

[RobH]

7 minutes ago, Firefly said:

Another can of worms, is it better to have the controller in the out from the engine or inlet. Answers on a post card please. 

No postcard but the answer is it doesn't really matter.  The only difference is the set-point will need to be different. 

6 minutes ago, Steven Whitaker said:

And in addition to my request for a link, what temps should the fan come on and off please?

There is no single answer.  ON somewhere above the normal running temperature so the fan is not running unnecessarily. OFF is a function of the switch hysteresis and is not normally adjustable, but it will be lower than the ON temperature. 

[Firefly]

     Thanks Rob, that was the conclusion I came to. Fitting it in the top hose was the most convenient, so that is where it lives. I asked because the Spitfire Roger referred to is in the inlet to the engine, i.e. bottom hose.

[james christie]

Just to add a few bits of practical info. 
The Otter switch comes with options as to the temperature when it switches the fan on. Mine is 82°C.

Unless you have greater brazing skills than I, it might be worth buying the down pipe complete with the boss for the switch. https://www.moss-europe.eu/fr-fr/pipe-water-return-stainless-steel-130039sst
I too went to the Otter switch arrangement as the original Revotec proved to be faulty. Otherwise I find the Revotec kit excellent and reliable.

james

[Steven Whitaker]

1 minute ago, james christie said:

Just to add a few bits of practical info. 
The Otter switch comes with options as to the temperature when it switches the fan on. Mine is 82°C.

Unless you have greater brazing skills than I, it might be worth buying the down pipe complete with the boss for the switch. https://www.moss-europe.eu/fr-fr/pipe-water-return-stainless-steel-130039sst
I too went to the Otter switch arrangement as the original Revotec proved to be faulty. Otherwise I find the Revotec kit excellent and reliable.

james

Great info.  Many Thanks.