Topping up coolant in a TR6

[Dieter H. Marschall]

Good morning all,
I know, this is "off topic", but I would like to read your opinion: On my TR6 I have added a screw to the top of the top of the thermostat housing, so that I can top up my cooling system here - at the highest point of the system.
Now a Triumph mechanic told me off, saying that this way I am adding too much coolant, which would raise the pressure and endanger the tubes. He told me to top up the system by pouring the coolant into the expansion tank.
I am of the opinion that any excess coolant in the system would be pressed into the expansion tank and not do any harm.
Now I am intrigued to learn, what you mean here.
Best wishes,
Dieter - from Germany.

[len]

hi Dieter
I too have a Tr6 and I fill up by the rad only, which leaves the top hose basically empty, enough room i guess for expansion. Makes no sense to me to touch the overflow bottle at all..with respect I wouldn't fill the top hose as you have done, but understand why you have
Len

[Dieter H. Marschall]

Len,
This filling up at the thermostat housing only works with a housing from an old Ford Escort. They have an extra thread on top for a sensor. When you blank this thread with a screw you have the opportunity to use this for filling up the system without any air left in the system...
Dieter.

[trunt]

From my reading there needs to be some air in the system for expansion, the older cars used the header tank as a place to hold that air and sized them accordingly. (My 67 MGB just spits out the excess onto the floor, pointless filling it to the top!) later cars had pressurised overflow bottles like the stag, but there is still air in the expansion bottle, even modern header tanks have an air cushion, so they can reduce the size of the radiator header tanks.

The only thing that does not seem to follow that logic is the recovery tank system, it spits the water out then sucks is back again, maybe...

Terry

[Phil S]

yet Citroën have bleed screws built into the high points of the hoses to allow bleeding, once a system reaches the pressure set by the rad cap it will spit any excess out

[RobinLegin]

My 1955 Alvis just spits out any overfilled water in the radiator. It is a non pressurised system perhaps unlike the TR 6.

[flying farmer]

The radiator cap will prevent any over pressurisation so there is no danger of damaging the hoses.

As the coolant expands it will blow out any excess, how much air sucks back is very dependent on the integrity of the upper seal under the rad cap. If it is ok the system should stay full of water.

When I fitted the Stag engine to my TR I blanked off the original radiator cap by fitting a circle of rubber (cut from an old Wellington boot) under a 22lb cap, then used a 13lb cap on the header tank

Neil

[stag8manod]

I have added plug to the top of thermostat housing on my 1500 Spitfire for final top up, has worked well for 20 plus years.
Cheers Ian A