Mark 1 radiator pressure cap issues

[Niall]

Hi everyone, would welcome any comments. I have a mark1 and I just fitted the Stagweber header tank. I have also fitted the Tony hart supergill rad. I have a 20lb pressure cap on the header tank and a 13lb pressure cap on the rad. I started the car for the first time today and didn’t have any leaks which I was very pleased about but when I switched off the engine, coolant started to leak from the 13lb pressure cap on the rad. I made the mistake of taking off the rad cap and coolant game gushing out! Should I now fit a 20lb cap to the rad?

Thanks in advance.

[Bakdraft007]

Hi everyone, would welcome any comments. I have a mark1 and I just fitted the Stagweber header tank. I have also fitted the Tony hart supergill rad. I have a 20lb pressure cap on the header tank and a 13lb pressure cap on the rad. I started the car for the first time today and didn’t have any leaks which I was very pleased about but when I switched off the engine, coolant started to leak from the 13lb pressure cap on the rad. I made the mistake of taking off the rad cap and coolant game gushing out! Should I now fit a 20lb cap to the rad?

Thanks in advance.

Funnily enough I have just fitted the same Stagweber tank to my MK1.. and had a post running .. its on the next page

I would say you need the 20psi cap on the radiator (or a blank from LD) I take it you sealed off the expansion pipe coming from the radiator to your original expansion bottle?
The 13psi goes on the stagweber tank. see pictures of mine on the post. I connected in where the tap is (used to be ) on the radiator

[Niall]

Many thanks. Yes, I have blanked off the expansion pipe (that was in the stagweber instructions). That’s a good idea to swap the rad caps around so that the 13psi one is on the header tank as the header tank has the drain off tube which I have just put down to the wheel arch (for any excess).

[Bakdraft007]

Many thanks. Yes, I have blanked off the expansion pipe (that was in the stagweber instructions). That’s a good idea to swap the rad caps around so that the 13psi one is on the header tank as the header tank has the drain off tube which I have just put down to the wheel arch (for any excess).

Funnily enough I spoke to Chris at Stagwebber and the blanking off that tube he had not thought about on a Mk1.. where it says that in the instructions he meant for a Mk2... but its still correct of course. I put the drain off tube on the stagweber back to the original expansion bottle.. as why not? if it ever leaked, why posion the environment and anyway catch it and poor it back in the weber tank

Here is mine... note the crafty way I have connected the tank output to the place where the tap goes on the radiator, this prevents any potential bypassing

IMG_1635.JPG

[jbuckl]

Oh I see thanks ....it was the old expansion pipe.
For a full flow header tank system, the outlet from the tank should be routed into the low pressure / cold side of the system.
Hope to post a diagram tomorrow.
sorry to hear of all the other issues too.
Fwiw I fitted a header tank in 1992 to my stag.
Then removed it after fixing the root cause of the cars cooling system issues. ‘Header tank free since 1993!’
As far as can be established , triumph canley invented the full flow header tank system in the late sixties/early seventies on engine testbeds to automatically eliminate cooling system air locks.
Subsequently adopted by many oems.
Many header tank systems fitted to stags shown here don’t have the pre-requisites to work properly sadly, but don’t harm either.

[mopoole]

Oh I see thanks ....it was the old expansion pipe.
For a full flow header tank system, the outlet from the tank should be routed into the low pressure / cold side of the system.
Hope to post a diagram tomorrow.
sorry to hear of all the other issues too.
Fwiw I fitted a header tank in 1992 to my stag.
Then removed it after fixing the root cause of the cars cooling system issues. ‘Header tank free since 1993!’
As far as can be established , triumph canley invented the full flow header tank system in the late sixties/early seventies on engine testbeds to automatically eliminate cooling system air locks.
Subsequently adopted by many oems.
Many header tank systems fitted to stags shown here don’t have the pre-requisites to work properly sadly, but don’t harm either.

Interested to know what "root cause" was and what are "pre-requisites to work properly"
TIA
Maurice

[jbuckl]

Interested to know what "root cause" was and what are "pre-requisites to work properly"
Root cause:-cylinder pressure in cooling system (slight head gasket failure)
Pre-requisites :- feed into tank should be from hi pressure side & small pipe above tanks return; return from tank to system should be to low pressure side & larger hose.

[mopoole]

Thanks
Maurice

[Bakdraft007]

Hi everyone, would welcome any comments. I have a mark1 and I just fitted the Stagweber header tank. I have also fitted the Tony hart supergill rad. I have a 20lb pressure cap on the header tank and a 13lb pressure cap on the rad. I started the car for the first time today and didn’t have any leaks which I was very pleased about but when I switched off the engine, coolant started to leak from the 13lb pressure cap on the rad. I made the mistake of taking off the rad cap and coolant game gushing out! Should I now fit a 20lb cap to the rad?

Thanks in advance.

Interestingly after finally getting mine back together.. (repaired radiator, Thermostat and repaired Thermostat housing) I fitted the 13psi cap on the stagweber tank and it also leaks? If it wasn't for the new clear tubes and there being fluid in the original bottleI might not have noticed. Reving the engine you can see the fluid in the origibal bottle being sucked back and forth.

Why it leaks is a mystery as it didn't in the old configuration, or at least I assume so.

So either its leaking because I have too much fluid in the stagweber tank although I left an airgap of about 2cm and maybe it needed more of a gap or somehow more pressure is generated.

This lead me to think about fitting the 20psi cap. Then I discovered that the 20psi cap is not the correct cap for the application I am using as it does not have a top rubber seal only a seal on the foot. This means it can never make a vacum if it releases pressure. I have ordered a new 13psi cap which has two rubber seals one on the foot one on the cap lid ,to see what that does.

[marshman]

I don't have a Stagweber header tank (or any other header tank) but I do know that as water heats up it expands and I am certain a 2cm "air gap" in the header tank (which also acts as an expansion vessel) does not leave enough space for the water to expand into. The water you see "leaking" is in my opinion excess water that there is not room for, i.e. you have filled it too full and not left enough room for expansion. You have two options. Remove some water from the tank (leave it 1/2 full woul be my guess) or simply leave it and when the sytem has expelled enough excess water it will no longer "leak".

Under normal running conditions in this country in the winter you should not see anything like 13lbs of pressure in the system unless the car is running hot.

Roger

[Bakdraft007]

I don't have a Stagweber header tank (or any other header tank) but I do know that as water heats up it expands and I am certain a 2cm "air gap" in the header tank (which also acts as an expansion vessel) does not leave enough space for the water to expand into. The water you see "leaking" is in my opinion excess water that there is not room for, i.e. you have filled it too full and not left enough room for expansion. You have two options. Remove some water from the tank (leave it 1/2 full woul be my guess) or simply leave it and when the sytem has expelled enough excess water it will no longer "leak".

Under normal running conditions in this country in the winter you should not see anything like 13lbs of pressure in the system unless the car is running hot.

Roger

There might be a bit of that happening especially at first as its difficult to judge how much to put in, but even with a good airgap and it having cooled. When you reve the engine you can see fluid from the overflow bottle moving up and down the overflow tube, which implied the cap is not sealed properly on the stagweber tank, hence I am ordering a new cap. Still, early days I will monitor it for a while and feedback.

In many ways that the joy of having an older car, it would be no fun if it ... well just worked.