thermostat

[RogerH]

For the adventurous - when you fit a Davies-Craig electric water pump you get rid of the thermostat.

the pump starts off in a pulsed mode that I guess simulates the thermostat restricting flow until things get hot in there.

LJ,

you're still with us despite the shenanigans of the committee.

 

Roger

[Z320]

Hi everyone,

 

I already drove some miles in 2018 and want you to tell what I did and realised on my TR4A.

 

This is the sensor in the thermostat housing,

that's the temperature going to the radiator or through the bypass.

Next you see the sensor in the water pump housing, that's the temperatur going into the engine to cool it,

mixed with hot water from the bypass to protect the engine from too cold water from the radiator.

Last the sensor in the radiator return pipe, that's how the water comes back from the radiator.

Actually I use a 71°C thermostat as told in the workshop manual, but the modern one left,

not a skirded bellows thermostat. It beginns to open at 70,5 - 71°C and is full opened 10 - 12 Kelvin hoter.

Bore in the bypass is 8,5 mm on my TR4A.

The bypass is to have always water flowing through the engine to avoid hotspots there.

Like on old central heating boilers made of cast iron, there is not much difference....

That's what the sonsors tell me after a restart (brake of circa 90 minutes), thermostat just not open.

With the mixing cross rule it is easy to calculate where the water in the water pump housing is comes from:

84% hot from the bypass to save the engine from too cold water from the radiator, only 16% from the radiator.

After a short distance (or downhill) this happens: thermostat is minimum opened (or short before closing),

there is a mix of 40-60% hot water by the bypass from the thermostat housing and 60-40% cold water from the radiator.

When the temperature goes 5-6 Kelvin higher than the opening temperature, and the engine runs at 2.500 revs or more this happens:

all the water in the water pump housing comes from direct from the radiator, no water goes through the bypass, it does not play any rule anymore.

On this temperature and ideling revs about 5 - 10% of the water goes throuht the bypass,

with the temperatur 10 Kelvin higher than the opening temperature of the thermostat also no water flows the bypass on ideling revs.

 

At original bore 8,5 mm, that's fine and I keep it as it is. On my TR4A nothing else is necessary.

On TR2-TR4 this could be some different when the bore in the bypass has a larger diameter.

 

The advice to reduce the bore could perhaps be reasonable on a TR4A with a normal bellows thermostat, which is more a plug than a valve.

This could be another interesting experiment - but this is "senseless knowledge" because no one does this.

 

Thanks to my wife to make photos from the display while I was driving.

 

Ciao Marco

Edited April 16, 2018 by Z320

[Z320]

Hi everybody,

 

today we have been out on a lovely early summer day in the countryside with a TR4 and TR4A,

through forests, fields, wineyords, up and down, we cruised, drove fast and sticked in bad traffic.

Weather was 23 - 26°C, thermostat 71°C, sunny all day, no cooling problems at all.

 

Temperature in the thermostat housing most time was 75-78°C, not more than 80°C,

downhill very fast below 70°C, than all the water went by the bypass, the original radiator is a "cooling monster"! .

Bypass very often mixed 50/50%.

 

With a thermostat 86°C there would be a urgend need to mix ALL the drive MORE

water by the bypass to get a much and constant water throught the engine! The thermostat

would give little volume of HOT water to the radiator and mix with much water from the bypass

to a constant temperatur (at a weather like today).

 

And again: with the water 5 Kelvin hoter than 71°C and the car on the road the bypass does not rule.

All the water comes straight from the radiator, throught the pump back in the engine.

 

Next I drive a bellows thermostat with skirt and 71°C.

 

Cheers Marco

Edited April 29, 2018 by Z320

[Z320]

Hi,

 

out on a holidaytour at the Rhein and Mosel river I realise the result of the skirted bellows thermostat is absolutly disappointing.

 

I will put it out as soon as possible, but before I perhaps will get some stau experience at the autobahn on our way home. That could be interesting.

 

Cheers Marco

 

.

Edited May 5, 2018 by Z320

[Z320]

Hi, have some time to report today.

This is my 71°C bellows thermostat with skirt, bought as NOS AC on eBay UK.

I checked it several times: starts to open at 71°C, full opened at 79°C, stroke 9.5 mm.

 

 

It looks like a plug in the narrow thermostat housing of my TR4A, doesn’t it?

Special compared with a “modern” wax thermostat?

 

 

The skirt has a wide gap to the surface of the housing (and bypass),

it works NOT like tight closing valve, it´s more a unsealed "guidance" to another possible way.

 

Starting the engine and driving the car the temperature always jumps up to 80°C and more,

so the skirt should close the bypass very fast and hold it always close, as told by the workshop manual.

But indeed I realize this on my TR4A: the bellows-plug reduces the flow

through the radiator and forces the water “ALWAYS” through the bypass.

This is after a very short drive of only 2 miles at moderate weather:

more than 80°C hot, full open, but 72% of the coolant is running the bypass anyway.

 

 

This is about 10 miles later, moderate drive and after a short summer rain:

more than 80°C hot, full open, 48% of the coolant still runs the bypass.

 

 

About further 10 miles, driving downhill:

some degrees less 80°C, nearly full open, 74% of the water runs the bypass.

 

On my TR4A the coolant only runs NOT the bypass with revs about 3.500 and more

OR water return from the radiator more than 80°C (90°C hot in the thermostat housing).

 

Difference of temperature of coolant "in" and "out" the radiator is often 10 Kelvin or more.

With the wax thermostat only 4 – 5 Klevin – so double flow with the wax thermostat.

Probably the bellows with skirt in the 60-ies was much better than a bellows without skirt,

but I realize using a modern wax thermostat is the real improvement on my TR4A,

without anything else needed to do on the cooling system.

Next I want to drive a TR3 water pump housing

with my 71°C wax thermostat and see what happens.

 

Cheers Marco

Edited June 8, 2018 by Z320

[stuart]

Thats why a shrouded thermostat isnt required for a 4a as you see.

Stuart.

[Z320]

....hmmm, if you realize how the skirted bellows work on a TR4A pump housing, how could it work on a TR3 pump housing?

[Z320]

Hi,

 

this is the TR3 water pump and housing I was able to buy from a garage clearance.

 

Perhaps the heating on this TR3 did not work because of air trapped there, but I do not believe on trapped air, it was only

dust.

Interesting is this thread in the bypass, diameter approx. 14,7 mm, I guess it's 3/8 BSP, perhaps a plug?

 

But not there anymore for ages.

 

Ciao Marco

Edited June 21, 2018 by Z320

[Z320]

Hi everybody,

by accident I reconditioned the old water pump and want to put it in the car to see if it works.

Doing this I could also swap over to the TR2-4 water pump housing? Only a little more work to do....

 

Interesting to see: my pump housing has the wrong connector for the heater pipe, but therefore suitable olive and nut on the pipe (neg. x neg. = pos.).

Drilled the housing, made a plan surface for the seal, cut the thread 1/8" BSP, made a plug 1/8" BSP for the TR4A housing and swaped the thermowell to the TR2-4 housing.

  

Next year I start with my 71°C wax thermostat and no reduction on the bypass.

I know TRs driving this way without problems. Don't know what happens, I'm excited for any experience.

Ciao Marco

[Z320]

Hi,

half year is over and sadly I drove less miles until now than last year,

but all with the 71°C wax thermostat and the TR3 water pump housing with about 15 mm bypass.

That's no problem at all, 

some more water is running the bypass then with the Tr4A housing and keeps a always lovely flow through the engine.  

And when it is "warm" outside there are no cooling problems at all.

Tomorrow will be a very hot day up to 37°C!

Should I fit my 72°C bellows thermostat today with my 13 PSI rad cap (0.89 bar)? I've been told that does not work?

In the bellows seems to be a mixture of air and alcohol and the high pressure of 13 PSI compresses the bellow and closes it?

But the pressure of alcohol hoter than 78°C is 14.5 PSI, 13 PSI is the pressure of 105°C hot coolant with 40% Glykol.

When you do not overfill the rad / have enought air in it (mine does). That should work?

Any ideas? Can anyone follow my thoughts?

Ciao, Marco

[stuart]

The bellows thermostats dont like anything more than the standard 4psi cap.

Stuart.

[Z320]

Hi Stuart,

thanks for that, but it worked "well" , as well as the skirted bellows thermotat can work.

Weather sunny, 37°C, sportive drive, no traffic jam, 72° bellows thermostat, 13 PSI radiator cap.

Radiator temperatur 5-10 Kelvin more than with the 71°C wax thermostat, often 85 - 90°C, max 95°C.

No coolant went to the overflow bottle (always empty on my TR4A) as I have got enough air in the system.

Lower than 80°C the skirted bellows is mixing, mixing, mixing... never less than 50% of the coolant goes the bypass.

No problem, hoter the 85°C "only" 10 - 20% of the coolant goes the bypass, revs more than 3,000 only 10 - 5%.

Due to the TR2-3 manual it is full opened at 90°C.

I cannot explain how to get on this temperature (90°C) with a 4 PSI radiator cap.

Ciao, Marco

Edited June 30, 2019 by Z320

[BlueTR3A-5EKT]

Here is the Land Rover 74 degree  wax-stat version of the skirted thermostat.

Unipart Pt No GTS109 or Land Rover 532453 -     It fits a TR if you make up a  (about 15 mm thick) spacer to support the outer mounting flange.  The skirt then slides back to block the TR bypass passage when the thermostat opens.

http://expeditionlandrover.info/Thermostats.htm

On reading this I discover that Land Rover reduced the size of the bypass port to 10mm when they adopted the non skirted thermostats as standard. (introduction of the 110 model with 2.25 engine)

Genuines On ebay 12 euros  -   https://www.ebay.co.uk/itm/GTS109-Unipart-Thermostat-Land-Rover-74-Degrees-/380679309454

Repro Available Bearmach  https://bearmach.com/thermostat-br-0109

I have one but have never attempted to fit it, even though I have made up a suitable spacer to fit between housing and outlet cover to accommodate the thermostat. 

Cheers

Peter W

 

PS

photos of the LandRover thermostat adaption for TR

Edited July 5, 2019 by BlueTR3A-5EKT

[BlueTR3A-5EKT]

On 6/30/2019 at 9:01 PM, BlueTR3A-5EKT said:

Here is the Land Rover 74 degree  wax-stat version of the skirted thermostat.

Unipart Pt No GTS109 or Land Rover 532453 -     It fits a TR if you make up a  (about 15 mm thick) spacer to support the outer mounting flange.  The skirt then slides back to block the TR bypass passage when the thermostat opens.

http://expeditionlandrover.info/Thermostats.htm

On reading this I discover that Land Rover reduced the size of the bypass port to 10mm when they adopted the non skirted thermostats as standard. (introduction of the 110 model with 2.25 engine)

Genuines On ebay 12 euros  -   https://www.ebay.co.uk/itm/GTS109-Unipart-Thermostat-Land-Rover-74-Degrees-/380679309454

Repro Available Bearmach  https://bearmach.com/thermostat-br-0109

I have one but have never attempted to fit it, even though I have made up a suitable spacer to fit between housing and outlet cover to accommodate the thermostat. 

Cheers

Peter W

 

PS

photos of the LandRover thermostat adaption for TR

Photos added

[BlueTR3A-5EKT]

.....and it is not only TR with thermostats having bypass blanks that are troubled when the thermostat is removed.

from xm655 preservation newsletter   https://xm655.com/blog/wp-content/uploads/2019/06/Summer-2019.pdf

”The Douglas Sentinel tug has also been
receiving attention. A persistent
overheating problem appears to have
been due to the lack of a thermostat,
which had been removed before we
acquired the tug. As the system
incorporates a radiator bypass, the
thermostat is needed to blank off the
bypass as the temperature rises, and a
new unit has made the cooling much
better. We also cleaned up the exhaust
manifold flanges and fitted new studs,
gaskets and nuts, and the engine is now somewhat quieter than before.”

 

[Z320]

Hi,

back from a 400 miles weekend with moderate temperature (max. 25 - 28°C),

the 72°C bellows thermostat worked "well" with the 13 PSI rad cap,

exactly in the way I described it at June 30.

No heating / overheating problem at all, rad temp. most time 80 deg. C, max. 85 deg C.

Ciao, Marco

Edited October 12, 2021 by Z320

[BlueTR3A-5EKT]

3 hours ago, Z320 said:

Hi,

back from a 400 miles weekend with moderate temperature (max. 25 - 28°C),

the 72°C bellows thermostat worked "well" with the 13 PS rad cap,

exactly in the way I described it at June 30.

No heating / overheating problem at all, rad temp. most time 80 deg. C, max. 85 deg C.

Ciao, Marco

Thanks for the update.

That is very reassuring.

Peter w

[Lebro]

I use a 88° bellows type with shield all year round, & (calibrated) gauge sits on the 8 of 185 happily unless in traffic for more than a few minutes,

then the revotech electric fan kicks in & brings it down again. No mechanical fan.

Bob.

[Z320]

Hi Bob,

with thermostat first opening at 88°C you increase the power of the (hoter) radiator

but reduce the flow through the radiator. This is absolute no problem at all.

In my opinion it this case it is a very good idea NOT to limit the flow though the bypass

to have always as much water flow as possible through the engine.

Ciao, Marco

[Z320]

Tomorrow we have a short 2 x 50 km drive to a friend "cafe at the garage" and it will be hot weather.

Today I put the bellows thermostat out and drive without and due to that without skirt blocking the bypass anytime.

Bypass full open (TR3 Water pump housing), what will hapen? Will I have cooling problems?

[Z320]

Out without a thermostst today - and really amazed about what happened!

But frist two photos with the 72°C bellows with skirt from 2 weeks ago, weather was about the same on both days.

 

First photo, the temperatur a minimum lower than 80°C,

the bellows thermostat nearly full opened, water from the rad back 64.7°C "cold", but in the water pump housing 74.1°C hot.

Due to the mixing-cross-rule 10.6/16.0 = 66% of the coolant still flows the bypass! The skirt can not close it.

Second photo, the temperatur at about 85°C, the thermostat full opened,

water from the rad back now about 80.4°C hot, water in the water pump housing minimum hoter.

Due to the mixing-cross-rule 1.1/4.1 = only 27% of the coolant flows the bypass. This is never less, the skirt can not close the bypass anytime.

Today out without thermostat and to my surprice I found this!

The engine gets "hot" without any probelms to 75 - 80°C after 5 - 10 miles, maximum uphill was 85°C.

At photo 3 you see 1.4/4.1 = 34% of the coolant flows the bypass! Isn't this the same like 2 weeks before with 72°C bellows thermostat!  

But see what happens after only 1 mile downhill:

The temperature drops rapidly because there is no thermostat there to close the flow to the rad!

But anyway 1.1/3.0 = about 30% of the cooland flows the bypass!

 

Some kind of difficult to come to a final judgment....   

 

Edited July 22, 2019 by Z320

[Z320]

Hi,

for the last tests I have my 72°C wax thermostat in the TR3 Water pump housing again.

This is a photo from last weekend, sunny weather 30°C hot, standing in a waiting line with the engine ideling / coolant temperature getting hotter.

I found 3.7 / 6.9 = about 50% of the coolant going through the bypass!

Next is a photo from this weekend, weather about the same, waiting with the engine ideling for friends.

In the bypass a resistor, a solid plug of aluminium - with a 8.5 mm drill. Don't look at the absolute temperatur, condition was not exactly the same!

But you realize "no" water (0.1 / 3.4) run the bypass, all goes through the radiator.

 

Not so bad, but see the next photo while driving on 2.000 - 3.000 revs still 0.9 / 3.6 = 25% of the coolant goes the bypass.

In this situation I remember less flow through the bypass with the TR4A water pump housing,

meens with the resistor as part of the water pump housing and not as a resistor next to the thermostat housing....

This will be the last test next weekend.

Ciao, Marco

[Z320]

Was out this weekend for a 200 miles drive with friends.

Sadly we had low temperatures and rain, so I can only say the bypass did his job very well.

Nice flow through the engine while the thermostat was only minimum opened.

I hope there will be a last hot weekend this year.

[Z320]

Hi there,

this is another currently made photo:

summer - temperature about 28°C - stop and go in front of a traffic light at the Austrian mountains - engine peaceful  ideling at 900 revs.

My summer thermostat 71°C has fully openend (at 81°C), all coolant return from the rad (below) flows out of the water pump housing (middle),

there is no flow by the restricted bypass (original TR4A water pump housing, 8.5 mm bore), a massive flow with only 2 Kelvin difference.

My final advice:

the sleeved bellows thermostat was the best of its time and shure better than the not sleeved.

But is was a massive "plug" and forced always too much coolant through the bypass - despite the sleeve.

The sleeve cannot close the bypass at all!

All the positiv stories I've been told I found "relativ" and too positive.

You better fit a more modern wax thermostat and limit the bypass to 8.5 - 8.0 mm - but not less.

I found the bypass often more needed than more flow to the rad, the TR4 engine is a cold one and the rad is massive powerful.

A good benefit is caused my BMW 1602 fan and the tin housing around.

Ciao, Marco

Edited July 3, 2021 by Z320

[BlueTR3A-5EKT]

Just reviewed this very useful thread, my 4mm drill hole in the cork is really wrong.   Drilling the restrictor to 8-9mm is the way to go as proved by Marco’s investigations.

I now turn up brass plug with a 9 mm hole to fit the large hole type housing.   It simply taps into place.  Most owners now use the waxstat type thermostat.

 

Marco.   The internal thread in the TR2-4 water pump housing bypass connection is a modification advised in ‘More BS about TR’s. By Bob Schiller.    The idea was to buy a regular plumbing fitting and screw it into the threaded hole to block the tube.    This is aimed at TRs in hot states like Arizona.

Read it here.

.   https://drive.google.com/file/d/0B2H2NJt34OffMmE1YTU0YzctMTQyOC00MmJmLWFiZGItNTI5ZjI3N2NjZTIy/view?resourcekey=0-lXvz6nHUvMR_xQs2mCWxmA

Edited January 16 by BlueTR3A-5EKT