Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing +8 Cooling problem - help with diagnosis please

Jeremy I run a John Eales 3.9 in my 1980 +8 and have down for over 20 years. Car has done a load of miles all over Europe and in some extremely warm temps, 40C plus. It used to run very hot in traffic, boiled. In the end I fitted an Ali rad, header tank, kenlowe fan and oil cooler and overheating solved. Water temp will still climb from a norm of 90C to 110/120 but the fan soon brings the temp down. I have a manual override switch for the cooling fan so can preempt "impending hot situations". Oil temp is usually 60/70C but can rise to 90C on extremely hot days.
I would recommend having the water temp checked at the bottom of the rad, my Smiths gauge read 10C high. Water on the windscreen on mine came from the header tank pipe leaking under pressure and spraying (finely) up through bonnet louvres. The kenlowe is fused separately, fuse located next to fuse box by bulkhead. I need 25A, anything lower blows on start

Is this time for the Evans water Thread???!!!

Fitted a new aluminium rad in my 97 3.9 +8 as it was running a bit hot and got there to quickly when I removed the thermostat housing to put a new one in there was no stat in there to start with ? , I’ve only had the mog for less than a year so no idea why the stat would be removed but it now runs better and temp is as it should be and the new 14” fan brings it down in traffic

My car has a fan kick in at 95deg setting. The car is sensitive to ambient temperature.
Winter.....gauge shows 80deg.
Summer.......gauge shows 90deg when ambient is 20deg or higher.
The fan kicks in ok and drops the temp but more often in summer. Slow traffic easily causes the temp to rise to fan kick in temp.
I am tempted to fit a by-pass switch for summer use to increase airflow and reduce the fluctuation in temp.
The car does not overheat as the fan works fine......just sensitive to ambient temp.

Steve

My 1999 car which I assume is a similar spec to yours runs in the 90s, according the gauge, most of the time in summer. I have an 85 deg thermostat fitted and a deeper alloy radiator. During summer traffic jams, like the Blackwall Tunnel (one of the pleasures of living in suburban London!) the fan will be operating for most of the time. I think this late generation Rover V8 was specced to run at high temperatures in order to keep emissions down. I agree with Simon (and John Eales) that the optimum for the engine is 85 Deg , it may be possible to change the actual ruling temperature with a customised ECU (Lloyd etc ) but that would be an expensive option AND you might possibly incur emissions fails during MoT tests.

I too have rigged up a by-pass switch which I can now use when I observe the temperature climbing, and attempt to keep it down. I also operate it before stopping the car to try and alleviate the heat soak generated by switching off a vey hot engine by starting from a lower temperature.

Colin (Spanner Juggler) helped me spec the by-pass switch, and installation was very easy. I installed piggy back spade connectors on the otter switch and then took two light duty wires back to an unused switch on my dashboard. Once I had assembled the components needed it was less than a couple of hours job (even for me)

I now feel much more confident going through heavy traffic knowing that I have an additional control over the temperatures.

As you probably know anyway, the thermostat restricts coolant flow when cold to speed up warming of the cylinder head and combustion chambers. My guess is that a previous owner removed it in a futile and misguided attempt to overcome over heating by increasing coolant flow throughout the engine. Once it’s hot of course, the thermostat should be open anyway.
Your solution of fitting upgraded rad and fan are obviously the way to go.

In the Mini community it's accepted to drill three 1/8" holes in the 'stat base, it doesn't interfere with it's physical operation so the engine will warm up easily, but it allows more water flow, as the 'stat as you know is quite restrictive even when open...If I owned an 8, I certainly would try it

Drop an old one in hot water & you'll be shocked just how little the open area is compared to your general hose diameter

Conversely if you run an A Series engine without a 'stat cylinder 4 overheats

Last time I flushed my cooling system I took the stat out. It had the 3 small ( approx 3mm) holes in the plate to allow extra flow as ^^^^^^^^.

Yeah, I type too much... But I feel it is only reasonable to point out that the cooling fan can draw quite a large current, so much so that some here suggest they have it fused at 25amps..? With that as a possibility then it seems best if installing any by-pass arrangement which switches the fan DIRECTLY without a relay in circuit, that both the wiring and the switch are capable of carrying the ACTUAL current (load) of the fan...

With a relay in circuit, the relay`s internal CONTACTS carry the full load of the fan, and the Otter switch only switches the load of the relays internal COIL which is minimal and likely to be a fraction of one amp, thus nothing like the load of the fan.

Using light wires connected at the Otter switch and on to a by-pass switch that switches the relay COIL creates no real issue, other than IF the relay coil or the contacts inside the relay fail.... operating the by-pass switch will not bring on the fan..?

Feel free to correct any errors in my thinking, I come here to learn.

Luddite, I think you have it right. My bypass switch activates the relay and will not work if the relay fails. For this reason I carry a spare relay. It is a plug in relay and is easy to change on the side of the road. My original relay was a 30 amp rated relay and I replaced it with a 40 amp. So far with the bypass and heavier relay I haven't had any problems.

You could wire your bypass switch in at the fan wires at the relay and bypass the relay. Make sure you use heavy enough wire and switch.