Coolant temperature

[Dave Wheatley]

Most of my driving is in a rural, congestion free area, and I've done around 5000 miles since April. The temperature gauge generally runs at about a third of the scale up from the bottom.

Yesterday I encountered a couple of temporary traffic lights, and after 1 minute, the gauge was over half way up the scale. Pulled into a layby, kept ticking over to test the fan, and of course the temperature kept going up until the fan cut in, and brought the temperature down fairly quickly.

Question. Is this normal for a B?

No coolant loss since I fixed various small problems earlier in the year.

I'm running slightly retarded timing at 6 degrees static which could marginally cause increased heat.

[Charles Farran]

Hi Dave,
I have a 1980 Roadster (from new) & the temp gauge has always run at approx 1/3 of the scale when moving . In the current warm weather , when stationary either in a queue or not, the gauge rises quite quickly until the fan kicks in. As you apparently not loosing any coolant i think what you are experiencing sounds perfectly normal. (i assume you have checked that the expansion tank is approximately half full when the system is cold).
Incidently i changed to Sealed 4 life some ten + years ago & only changed the coolant 18 months ago following an under bonnet refurb. Any weeps are easy to spot (when tightening hoses etc) as the coolant is pink.
Cheers
Charles

[Dave Wheatley]

Thanks for the reassurance Charles.

Expansion tank remains at half full.

Small quirk - when I check the coolant level at the thermostat housing, it is always about 3/4 of an inch below the top of the housing. If I try to get it any higher, the coolant runs straight into the expansion tank!

Regarding pink antifreeze, I've been told that we should always use the blue stuff in a B!

[Charles Farran]

Hi David,

The Sealed 4 life is a coolant marketed by The MGOC . You do not mix it with water at all. (Apologies if you know that)! When i drained out the fluid (Sealed 4 Life) that i had had in the system for circa10 years as part of my refurb exercise i was amazed how clear it was & could probably have reused it. I am not aware of it not being suitable for MGBs ! Having said that i don't use the car for racing & it is not suitable if an ongoing leak requires topping up with water albeit in an emergency one wouldn't have much option as a temporary fix.
With regards to the level being 3/4 below the top of the housing , i take it you mean 3/4 below the bottom of the threaded neck. You might have a small air bubble, that would normally be purged during the heating up / cooling down of the coolant. I have always made sure the heater valve is fully open when refilling & squeezed the top hose at the same time. The process of purging air is also easier if you ensure you have a thermostat with a small breather hole with a butterfly float that lets the air out of the block & the fluid flow back. (Some after market thermostats don't have these & some simply drill a hole in the flat plate).
Worth checking that you haven't got a tiny leak from the drain hole below the water pump impellor as this is difficult to spot , particularly if you don't use a coloured coolant.That said, the more the car is used,the longer the pumps seem to last!

Cheers
Charles

[Vic Butler]

Whenever I check the coolant level in the thermostat housing it's always below the threads so I top it up and next time it's below the threads again. The level in the expansion tank is OK so now I don't bother.
The temperature gauge on my Stage 2 BGT reads near the centre (the stat is an 82C). If it reads higher as in a traffic jam the fan cuts in and brings the needle back to the normal reading so I just keep an eye on it to ensure there are no unusual variations.
I mix my own antifreeze using water from the water butt and blue ethylene glycol. This is a very hard water area in NW Hampshire.

[Dave Wheatley]

Thanks Charles and Vic.

It would seem then that my coolant temperature behaviour is pretty well normal.

Regarding the level in the thermostat housing, the 3/4" is below the top flat face round the screw hole, and if I try to bring the level up to the top, the coolant goes into the rad, and out again to the expansion tank. I've not had any significant loss in the 5000 miles that I have done this year - since replacing a weeping head gasket. Maybe the expansion tank is mounted a bit low, but it looks as if it has not been disturbed from new.

[Charles Farran]

Dave,
I think Vic's assessment is correct. Unless you can see that the expansion tank has been lowered, perhaps due to a previous owner replacing an inner wing which didn't have pre-drilled holes & then putting them in too low, then it is unlikely. On mine the top of the cap of the expansion tank (on an original inner wing) just fits below the channel where the bonnet edge sits in,so if yours does the same the height of yours will be the same. (I suspect because it is a pressurised system the actual precise height will make little difference).
Cheers,Charles

[Dave Wheatley]

Thanks Charles.

The cap of my expansion tank is quite difficult to get at on account of the lip that you mention. I suspect the tank setup is original.

[Vic Butler]

The cap on the expansion tank on my BGT is just below the lip on the inner wing and is difficult to get at too Dave. I know mine is original so your is too.

[Dave Wheatley]

Just thinking about the coolant level. On my car, the pipe from the radiator to the expansion tank goes in a straight line.If I increase the length of this pipe and put an upward curve in it, this would allow the level in the thermostat housing to reach the top before the overspill runs into the expansion tank.

Truth is I'm not at all concerned about the level being 3/4" below the top of the housing as the car has performed faultlessly over the last 5000 miles, but could the original when new pipe to the expansion tank have had such a high point built in?

All a bit esoteric I know:-)