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

Normally: my +8 runs at just above 80 on the temp gauge in most conditions. Occasionally in slow traffic will go to 100 and then the fan cuts in and it drops down a bit before going back to 80 when on the move again.

However: Last couple of runs out noticed the temp gauge settle at just above 80 then, whilst still running at 50mph, move up to 100 for a while before dropping back down again. On todays run out when it got to 100 i also got a few drops of water on the windscreen (no rain in sight) and there was some water around the front cowl.

So, I'm wondering what going on? Sticking thermostat? What temp do +8's normally run? This is a 1990 3.9 pre cat. Impending hose about to burst? Damaged radiator?

Appreciate the opinons of those here that have learnt along the way to help point me in the right direction! Many thanks. Jeremy

Is the level OK?

Some V8s have a "steam pipe" which runs from the thermostat housing to the inlet manifold. If you have one of these narrow bore hoses, make sure its not blocked.

I had a V8 in an MGB ant the temp gauge oscillated up and down quite a lot.

Water pump on its way out maybe?

Jeremy, I think the gauges are so inaccurate that it’s not really a case of what other +8s normally run at, rather an indicative reference point to see fluctuations.

My +8 (a 1996 3.9) has always indicated 95-100 degrees, going up to 115-120 when it’s hot. That was until it badly overheated recently and is now awaiting a new aluminium rad. I’d just had the water pump replaced so that shouldnt have been at fault.
Good luck with the fault finding.

That is (admittedly indicated) far too hot, a Rover V8 engine should be run between 80-90 degrees. Prolonged running at temperatures above this can cause softening of the heads behind the exhaust valve seats, detonation and pinking along with a significant drop in performance

I have upgraded aluminium radiators and fans on the shelf ready to ship

Simon @ SiFab.co.uk

Hi Simon, I’ve had the car for just over 10 years and it’s always indicated those temperatures, I’ve never had any pinking or performance problems and it’s always been serviced by BHM, so I’ve always assumed it’s just indicating wrongly. I’m no V8 expert though so I’ll get BHM to check it when they replace the rad.

Thanks All - appreciate the input, will take the car out again tomorrow for a longer run, having checked the water level before i leave, to see if I can learn more......keep you posted. Jeremy

I have a 2002 Gems 4.0litre car. The coolant temp (gauge reading) varies dependant on the ambient air temp. In winter it hits 80 when warms up. In summer it goes to 90-ish and higher when on stop/in traffic. The fan cuts in and drops it back ok. No signs of overheating. I have tried water wetter but negligible, if any, effect. The rad is aluminium and no coolant issues.
I have been toying with the idea of getting more air through the rad by using ducts/ scoop etc. for warmer summer driving.
Under bonnet gets quite warm! So some thoughts on that too. Bonnet rear catch extenders/ ducted airflow to the intake. Trouble is getting down to doing it! Maybe this winter.
The engine generates a lot of heat and two cast manifolds chuck it out with vigour!

Ran the car again this morning and noticed a small leak from the new radiator cap I put on a few weeks ago. The old cap had corroded around the pin that located the seal, so i replaced it. Put the old cap, that i had fortunately kept, back on and she ran as normal for 40 miles. Phew.

Steve
My 1995 +8 indicates similar temperatures to yours. But a number of years ago I had to replace the temperature sensor for the gauge. I bought a random sensor from a Land Rover specialist and the gauge has subsequently always read hot. Recently I have done some tests with a chart recorder multi-meter etc. and found that the fan comes on at 90degC and the temperature doesn't go any higher. What I need now is the correct temperature sensor for my VDO Gauge....