TR4a Cooling Problem

[d2alfa]

Hi,

I got stuck behind a tractor going up a long and steep hill at 1mph and the water boiled.

Hence I replaced the cylinder head gasket and put in a new thermostat.

On the first run the gauge showed the engine was getting hot and so I stopped.

Oddly the engine was very hot but the radiator was cold and I therefore removed the thermostat. The gauge needle on my return home showed no value.

I checked the thermostat in hot water and it appears to operate correctly.

What is going on please?

Has the water pump failed and how do I check?

David

[RogerH]

Hi David,

 you almost certainly had an air bubble in the block/radiator.

Remove the air bubble and all should be well.

Do you have an  electric fan fitted to the rad. If so have you got an over ride switch. These can work very well when stuck in TRaffic.

 

Roger

[Z320]

Hi David,

you fitted the thermostat the correct way?

Ciao, Marco

Edited August 22, 2021 by Z320

[stillp]

23 minutes ago, RogerH said:

 

Do you have an  electric fan fitted to the rad. If so have you got an over ride switch. These can work very well when stuck in TRaffic.

 

Not if the radiator is already cold Roger!

Pete

[d2alfa]

Thanks guys,

It is a TR4a and I changed to a bellows thermostat because I understood that type allowed more flow.

In the past I removed the original fan and fitted an electric (push eg in front of the radiator) fan which should have come on.

David

 

[d2alfa]

I think you are saying that I have an airlock such that the radiator stays cold and the fan will do nothing to help.

The temp gauge shows nothing because that part of the system currently has only air present.

Am I correct?

How do I get the airlock out please?

[stillp]

1 minute ago, d2alfa said:

 

How do I get the airlock out please?

Jack the front up, run the engine with the radiator cap off, heater valve open. If nothing happens try squeezing the hoses.

Pete

[Malbaby]

Assuming the water pump and the thermostat are OK.....I would remove the radiator and take it to a radiator shop and have it tested.

Also change the pusher fan to pull type.

If you are really keen you could do a narrow belt conversion at the same time....Harmonic balancer [Aussie Holden with some extra modifications], water pump [6 cyl TR] and alternator....Does not cost a lot of money.

[Z320]

Hi David,

while driving behind the tractor your gauge showed HOT?

For your drive home you put out the thermostat?

This worked, no boiling and the coolant temperature was very low?

This is because cooling worked and water pump and radiator are very effective!

So  - why should air be locked anywhere?

In my opinion air locked is never the case, it is the final hope of desperation.

Ciao, Marco

Edited August 23, 2021 by Z320

[rcreweread]

David - if you do suspect your radiator, how about the Alicool alloy one with a fitted fan I have for sale in Classifieds? It's brand new and a bargain at nearly £200 less than it's normal price

https://www.tr-register.co.uk/classified/4259/TR4A-Alicool-Alloy-Radiator-with-Fitted-Spal-Fan-PCoated-Brand-New-For-Sale

Cheers Rich

[Z320]

Hi David,

after reading your posts again (mostly perfect) I perhaps know what happened.

You had a wax thermostat (correct for the 4A) and fitted a bellows because you hope for more flow.

This is not the case, the bellows is a horrible plug, please see the photos.

With the 4A you have a 7 PSI rad cap, or like mine a 13 PSI one.

With the new cylinder head seal you may have toped up the coolant level as much as possible to get as much air out of the system.

With less air in the system the pressure raises very fast and high up to 7 or 13 PSI.

The bellows is mostly filled with simple air and alcohol, steamed with the heat.

The steamed alcohol opens the thermostat – but the higher pressure (because of less air)

and higher pressure rad cap compresses the thermostat (the air in there) until it is closed!

My advice:

-          kick the bellows in the bin

-          fit any wax thermostat (all are not pressure sensible) you want

-          let enough air in the rad, don’t overfill it

-          don’t believe “you have to bleed the system” – whispers

All will be good very soon.

Ciao, Marco

Edited August 23, 2021 by Z320

[d2alfa]

Thanks guys,

Just for info some years ago I fitted a narrow belt conversion with a damped pulley and alternator.

I will order a wax thermostat and try again

David 

[DavidBee]

Don't forget the restrictor in the bypass when you do. Inexpensive, very effective.

[Z320]

The correct TR4A water pump housing has already a reduced bypass diameter of 8.5 mm,

have a look and if this is the case: don't worry

Edited August 23, 2021 by Z320

[DavidBee]

9 hours ago, Z320 said:

The correct TR4A water pump housing has already a reduced bypass diameter of 8.5 mm

Excellent to know! Thanks,

David

[d2alfa]

Yes it looks like the correct TR4a water pump housing is fitted; I added an uprated pump some years ago.

Thanks

David

[Andy Moltu]

If it didn't overheat with the thermostat removed, you have likely answered the question as to what caused it to overheat. The stat may seem to function but has failed the real use test!. It may be that the mechanism is a bit tight and when there is a bit of load when the housing is clamped up or simply pressure from the water pump it stick closed.  I recall 30 years or so back I had a run of stat failures on a Scimitar GTE with the Ford Essex engine.  This pretty much confirms the water pump is working as thermal syphoning probably won't be enough with no stat in.

The bi-pass hose should prevent air pockets behind the stat.  (You could fit a stat with a jiggle pin - they use these on the Stags - the plate of the stat has a small bleed hole with a little brass thing passing through it - presumably to stop it clogging up to allow any air beneath the stat to be pushed through and hot water make good contact with the stat.)

Sounds like you have been unlucky and had one fail and replaced with a dud.