Moss kit car/Herald 13/60 cooling system query

[Steve J]

Hi folks,

First post here having just acquired a Moss Malvern kit car which was built in the 1980s using a Herald 13/60 as the donor for it's engine and chassis.  It's a bit of a rattly old contraption and appears to have been bodged about, but I'll give it a fair chance.

My query is with the cooling system which includes no less than three pressure caps- one on the radiator itself, one on the thermostat housing (with ominous rusty water stains) and another on the expansion bottle. The one on the thermostat is rated at 13lbs but the other two are unmarked. Any idea what the ratings on these should be?

Many thanks,

Steve

[glang]

oh dear that is a mix up and means anything could happen during warm up when the coolant expands or indeed if overheating occurs. Does the overflow pipe from the thermostat housing go to the bottom of the expansion bottle? Where does the overflow from the radiator go to?Unusual two of the caps dont have ratings stamped on them☹️

[JohnD]

The caps on the rad and thermostat should be the same, as they will see the same pressure.    Perhaps the thermostat one could be higher than thecrad to avoid the spill you have seen.

The expansion bottle should not see  high pressure at all, in fact I think (glad to be corrected!) that it should 'breathe'.    Coolant enters the bottle if the rad overflows, and can take it back as the system depressurise.

John

[Steve J]

Thanks for the replies gents, much appreciated. It does seem a rather convoluted system compared to earlier Heralds, which I'm guessing just had the one main cap on the radiator, a standard thermostat housing and no expansion bottle.  The photo shows the 3-way junction at the bottom of the rad with one pipe to the water pump and another up to the thermostat housing. I think this is all going to need a good flush through judging by the orange stains...

The rad has the usual thin overflow pipe clipped to the side and dangling down. The overflow from the thermostat does indeed go to the bottom of the expansion bottle.

 

[glang]

It looks to be a FWD engine thats been used (serial numbers RD/RF?) but those two large hoses are mystifying as the should both go to the radiator top tank!

[Clive]

3 hours ago, JohnD said:

 

The expansion bottle should not see  high pressure at all, in fact I think (glad to be corrected!) that it should 'breathe'.    Coolant enters the bottle if the rad overflows, and can take it back as the system depressurise.

John

That expansion tank does pressurise, it is the same a dolomite and countless others from the same era. 

Ideally replace the others with higher pressure caps or seal them. 

It may be worth changing things a bit. It may be possible to get rid of the thermostat housing one by using a std herald type? At the moment I think the big hose from that is acting a a huge bypass, far too large. 

In fact, I am head scratching about what would be best. 

[Steve J]

Thank you, I really appreciate your opinions on this. I'm so glad I joined the forum! I did wonder whether I could simplify things by fitting a normal thermostat housing and simplifying the plumbing. It wouldn't cost much to acquire the parts to experiment. There is a temp gauge in the car so I could monitor the results.

[Clive]

I have been thinking. 

Yes, changing the thermostat housing to a herald/spit one would be good. But ideally I would be adding an air bleed takeoff. If you have some taps to thread the ally housing you can get all sorts of sizes of hose tails. I used 8mm hose on my car (dolomite, not that it matters)

Ideally that would feed into the top of an expansion tank. From the bottom of the expansion tank a larger bore hose (I used 3/4) into the bottom rad hose. This setup cycles water through the expansion tank, constantly removing any air bubbles. If you wanted to, a second small hose from the rad overflow pipe could be added, but you MUST fit a seal cap to the radiator, not a normal rad cap. 

Plenty of cheap expansion tanks on fleabay, I used one off a corsa.