Your questions answered: D3 EGR Valve, Ninety Revotech fan

Temperamental Disco 3 is cured

In a previous Tech feature we heard from reader, Brian George, whose Discovery 3 refused to accelerate a couple of miles after driving away. Then, once the auto box kickdown had been used to make the vehicle accelerate, all was well until the next cold start. We were unable to identify the problem, short of suggesting having a diagnostic check done while the fault was existing. The problem is now cured, and Brian has sent details of the eventual solution, as identified by his garage.

LRM Reader Brian George reports: “After experiencing this loss of acceleration while the engine was warming up several times, eventually the engine light came on while this was happening. I was able to drive to my local garage right away and left the engine running while Ian (garage owner) used the diagnostic tool to see what was happening. He said there was no clear indicator, but there was a lot of chaff, and some indicated the Air Flow Sensor, but that also showed it to be functioning. So he cleared the engine light and the car ran okay, then he changed the air flow sensor a couple of days later. The car ran okay for a few weeks until the cooler weather, and then the fault came back again.

Next, I booked the car in for the engine oil sensor to be changed (you suggested this might be the problem), which included the oil and filter to change as well, early in January this year. Again the car ran okay for about ten days. Then after I had driven about seven miles and parked the car, the engine light stayed on after starting up again, and the problem of no acceleration occurred as well, until the engine was back up to normal temp. This was a Saturday, and the garage was closed, so I had to drive home with the engine light on all the way, but the car ran okay. On the Monday, I started the car up with considerable difficulty – it kept stalling, and had clouds of white smoke from the exhaust with a strong diesel smell until it warmed up a bit, and then I drove the five miles to the garage for a diagnostic test.

With the engine still running, the tester was connected and it came up right away with EGR valves sticking! The engine light was cleared, and the car ran okay, and I booked it in for new EGR valves to be fitted, for which I had to wait until early February, as the garage was fully booked.

On the advice of the garage owner, I took the car for a fast drive up and down our local dual carriageway a few times to try to clear the valves. Anyway, the engine light stayed off during this time, until I had new EGR valves fitted; and now the car runs trouble-free. No hesitation in acceleration anymore. So, fixed at the third attempt, and it turned out to be quite costly, too.

The V6 diesel EGR valves are difficult to replace, hidden deep down on each side of the engine. This one is visible because the vehicle body has been lifted off the chassis.

Exhaust gas supplied from the EGR valve passes into the engine air inlet via this nozzle. The treacle attached to this also gums up the EGR valve as it passes through

The cause was probably too many short runs, and cheap diesel fuel. So now I am using ‘super-diesel’ and I get the car up to motorway speeds whenever I can. We do not have many dual carriageways in Cornwall to drive fast on…”

Petrol Ninety fans

I have a 1989 petrol 90 on the verge of a full rebuild and I am thinking of fitting a Revotech fan. I currently run it with engine-driven fan and full cowl. Revotech does two fans: a blower (in front of rad) and a sucker behind rad. I don’t think the fan will sit under the cowl at the rad, so should I fit the blower and keep the cowl, or fit the sucker? And is the cowl now irrelevant, as there would be no engine driven fan? I have been told the cowl is there because of the distance from the fan to the rad.  Mike Hurley

Replacing the standard fan for a compact radiator-mounted electric version without the original cowl provides plenty of working access in the front of the engine bay

Ed Evans replies: I would recommend fitting the suction fan behind the radiator. It could be argued that placing a fan and its fittings in front of the rad may marginally reduce the radiator’s cooling effect when the fan is not running, though the effect is negligible. Also, placing it behind the rad in the engine bay means it’s more accessible for maintenance, such as checking the wiring.

The standard cowl prevent fingers contacting the moving original fan, but this will no longer apply, and the electric fan is well guarded (though keep your fingers away from the ancillary drive belt). As you say, the cowl increases air flow efficiency between the radiator and the fan, but this no longer applies with the electric fan fitted. It also helps cool the outside of the engine by directing the air flow towards it but, with a 2.5-litre petrol engine, the absence of a cowl won’t be noticed.

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