75 series III high temp issue with ac on

[ernest.irw]

I have a 1975 series III SWB with original 3 bearing 2.25 L petrol engine. In July 2017 I fitted a new radiator and three years before that I’ve replaced the water pump, I’ve also fitted 82c thermostat recently. Because I lived in tropical country I really need to fit an air conditioner so I installed Sanden 508 compressor in September 2017. I knew that Sanden 508 compressor robs about 8hp and would probably put quite a load of the engine but I believe it will give cooler air and I believe the rover engine will endure the load.

I took my rover to a modification workshop and they did the brackets, belt route, pulley, the power steering pump repositioned. The ac condenser placed 1.5 inches (4cm) apart from radiator and installed a 12 inch Mercedes Benz W202 electric pusher fan in front of the ac condenser. The original engine fan is tight, no movement.

After I got back my Rover from the workshop I noticed that the original temperature gauge reads quite high about ¼ below the red line after two hours of driving in the highway and it was a hot afternoon. At first I did not trust the original gauge, so I fitted a third party water temp gauge and installed the sender unit at the radiator hose and it turns out that the original gauge is working properly and I guess the when the needle is at the middle of the gauge (N), it is at 75c (167 F). Now the engine running temperature with the ac on is always read between 82c to 90c (179F to 194F). On one Sunday afternoon I drive around my series III for about 45 minutes and the water temp gauge reads at 85c (185F) and soon after I got back and switched off the engine the temp rises due to hot weather that day and the engine bay ambient temperature rises to 90c (194F).

My question is, is it ok if I have 85c-90c (179F to 194F) running engine temperature and is it ok if I push it up to 95c (203F), because the original temp gauge often rises up to ¼ near red line during hill climb?

What is the recommended running engine temperature for land rover series III?

[mearstrae]

You kind of answered your own question... If you want to run temps of 82c to about 90c use the the 82c thermostat. if you want to run at 72c to 80c use a 72c thermostat. These thermostats aren't exact and move up the temp scale, so the temp can vary several degrees while running. You need to run the thermostat that keeps you from overheating and/or vapor locking your carb. Only fuel injected/computerized cars care about specific temps when running. And...the load of air conditioning can also raise the running temp no matter what thermostat you use.

'99 Disco II
'95 R.R.C. Lwb (Gone...)
'76 Series III HYbrid 109
'70 Rover 3500S

[ernest.irw]

I see, Thanks mearstrae for the great advice!! i will definitely change the thermostat to 72c. You mentioned vapor lock and it is exactly almost happen during high temp and I thought it was fuel pump problem since I used an electric fuel pump. But I’m a bit curious about the limit of land rover series 2.25 L petrol engine, they have been used in the Sahara desert for journey that covers thousands of miles and I think those engines will reach high temp above 90c. Will the engine endure at 90-95c (just below the red line) without any damage? Or vapor lock is the limit?

[ernest.irw]

Here are some images of AC installation

Engine Bay


Extra fan


Cabin AC evaporator

[mearstrae]

Will it take 90c? Yes, but why stress and engine that way if you don't have to? You've added enough stress by putting an air conditioning unit on the poor little 2.25L engine. And vapor lock may haunt you at the higher temps, the electric fuel pumps seem to help prevent this, if used alone (removing the mechanical pump and using only the electric one, and moving the fuel lines to a cooler location). Nice, neat install by the way.

'99 Disco II
'95 R.R.C. Lwb (Gone...)
'76 Series III Hybrid 109
'70 Rover 3500S

[ernest.irw]

Thank you very much for the wisdom mearstrae.