Vixen 2500 - cooling issue

[matchless_mike]

My 1971 2500 Vixen has been back on the road for a couple of months but is still undergoing what you might describe as 'reliability trials'.

I'm a bit concerned about the engine temperature when in slow moving traffic - the temperature gauge rises extremely quickly and the fan cuts in and this happens in cold weather!(How will it cope in hot weather ?) The car is fitted with a standard water pump. The radiator is fairly new as fitted by the previous owner but is of unknown manufacturer and spec - its nothing special. I notice that the same engine in the TR6 has a bigger radiator as space allows on those cars.

Is running hot common on the 2500 ? Do I need a higher spec radiator ? Any advice welcome.

[Adrian@]

Has your car got AC or smith gauges? if Smiths look for the electronic voltage stabiliser (see the link on the previous Vixen thread) and replace yours 1st so as to get the gauge reading correctly. Adrian@

[matchless_mike]

The car is still fitted with a full set of AC gauges - all seem to stable and working. The gauge holds steady at about 85 to 90c when being driven out on the open road.

In order to check it , where does this voltage stabilzer live exactly ?

[Adrian@]

Your AC gauges do not have a stabiliser but the Smiths gauges do and this gives this type of issues...I would look at adding an expansion tank into the system (as the late M series car) Adrian@

[matchless_mike]

I know the type of expansion tank you mean - it's mounted vertically on the 2500m but lays on its side on the vixen 2500.

Interesting that you mention the expansion tank because I did not refit the original as it was rotten and I could find a suitable replacement. Alternatively I fitted an in line piece of solid pipe with a radiator cap. Just beneath the cap it a 3/8'' spigot for a pipe to vent into a plastic bottle.

So I need a steel expansion tank ? Is not having one affecting the cooling ?

[Adrian@]

I think so, PM me with a picture of your engine bay with the current layout and I should be able to work out where/what need adding (the last one I did had a vent on the top of the thermostat housing that was converted to a blanking plug to vent the top of the engine), and a additional vent of the headed tank.
Adrian@

[matchless_mike]

Thanks - will get a couple of pics done this evening.

[matchless_mike]

Here's the current layout.

[Adrian@]

I would want a bleed vent (drilled, tapped and plug) on the thermostat housing 1st and another test of the system to check what difference, if any, by ensuring that all the air is out... then if that did not help, a vent pipe linked to the top of the rad from the filler cap you have (non pressured cap),along with an expansion tank in place of the overflow bottle with a 13lb cap...
Adrian@

[JeffT]

Mike- That looks like the stock radiator(matches mine). Not the original fan, did you add that electric fan?

-Jef

[matchless_mike]

Hi Jef

The radiator was one a the new parts that the previous owner had fitted - pleased to hear it is most likely the correct style. I added the fan to replace an earlier effort which was probably added about 30 years ago judging by the date stamp on the motor.

I have just found a guy who will make me a header tank in the same style to replace the rotten lump I inherited. Hopefully one step in the right direction.

[eric0]

Have you got an oil cooler fitted?

The Triumph straight six does suffer from poor cooling jacket design. I have a 2500M which i've just put back on the road. I havn't got the cooler refitted yet and like yourself the fan cuts in in traffic.

As other people have said the vent on top of the thermastat, venting in to a expansion tank/swerl pot mounted as high as possible is your best way forward.

You can get uprated pumps from people like Moss with 5 vein Impellers.

[matchless_mike]

Expansion tank in process of being re-made (copy of the original). May well go for an oil cooler as I see they are readily available for the TR6.