The first time my Rover displayed symptoms of fuel vaporisation was in the Summer of 1986. I was on my P plates and had taken the Rover on a trip to northern N.S.W. On one hot day,..over 30 degrees C after having stopped at a "lookout" upon restarting the car bunny hopped a bit before settling down. At the time the Rover still had the original 2-core radiator from 1974 with no additional transmission oil cooler. The engine fan was and still is the 13 bladed nylon arrangement on a viscous coupling, which limits fan rotation to 2500 rpm. The fuel pump at this time was also the mechanical AC.
No further vaporisation occurred until 1990 when it hit out of the blue and continued well into 1991. My Rover along with scores of others that previously had little experience of such a phenomenon were now all in the same boat. I recall on one Winter's day. Overcast and 9 degrees C. The needle was in the white and it started to vapourise,..I mean seriously...how ridiculous. I stopped, opened the bonnet,...the carburettor dashpots were stone cold...and it was vaporising. :shock: It was like a bad joke and not amused I was.
In 1990 I fitted an electric fuel pump beneath the tank to run in series with the mechanical pump. Operated by a switch, it remains off until needed. The cooling system had always been well maintained, flushed with a new fill of coolant every 12 months. The thermostat at the time was an 82 degree C which was really too warm for hot Australian conditions. On one occasion while driving back from Melbourne in Summer of that year, the ambient temperature was 38 degrees C so in the car it was close to 50 degrees C...too hot,. it started to vaporise at 60mph.. :shock: I switched on the electric pump and it cleared immediately.
The following year the vaporisation problem disappeared. My Rover, a friend's Rover and all the people I knew from the Rover Owner's club...the problem vanished from their cars too. To this day it has never returned to my car. In 2007 not long before I had the 4.6 installed, I was driving through heavy traffic in Sydney, the ambient temperature was over 36 degrees C. The coolant temperature was just under 100 degrees C (almost nudging the red zone) and the engine oil temperature as measured in the coolest spot...in the bottom of the sump..reached 130 degrees C. Did it vaporise?....nope...did not miss a beat. With the 4.6..no problem either. I have been using 3 core radiators since the mid 1990s and a 74 degree thermostat to cope with the hot conditions and whilst driving last Summer, long trips over hundreds of miles, coolant temperature needle between the 8 and 5...engine oil temperature...100 degrees C...no problem at all. The fuel pump is still the mechanical AC, as I wished to retain it, even for the 4.6. The electric pump sits quietly, but I switch it on every now and then to make sure it still works, and then off again.
My view is that the problem at the time was directly related to the fuel, and what ever it was that caused the problem..was corrected. It affected so many Rovers at the same time and then just disappeared.
As for why Rovers in much cooler environs would experience such I can only point the finger at the fuel. I don’t dismiss other possibilities such as the cooling system, which should always be kept in good condition if reliability and longevity it to be expected. I feel however that the major cause is in the fuel.
You might be wondering if that is indeed the case why don’t modern cars also experience this. I can only imagine that it is directly related to the means with which the fuel is provided to the engine. Fuel injection system systems run at much higher pressures, and that will prevent vaporisation from occurring.
Ron
