Renault 25 Poor output from heater

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Renault 25 Poor output from heater

Post by oaklands » 04 Dec 2003, 21:12

Hi, this is my first post so please be gentle with me! My problem is this:
I have just inherited a 1986 Renault 25 GTS 2.0. There was no heat output from the heater at all so I tried changing the Thermostat. I now have some heat output but not much. I am thinking that I may have an airlock somewhere but, I don't know how to bleed the system. The Haynes manual mentions bleed screws but I can't find them! Any help would be most welcome. Thanks

alan s
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Post by alan s » 05 Dec 2003, 15:20

I can't speak for a Renault 25 but on most French cars per se, the bleed screws can be either plastic round things with screw slot in the middle or simply bleeders (nipples) as you have on hydraulic brakes.
Renaults over the years have had this idiosyncrasy of having the heater matrix higher than the header tank of the radiator, hence when the cooling system is filled, they tend to get this dirty big air lock in the heater matrix.
Standard practice on the old 16 series (which were known as possibly the worst example of this) was to fit a funnel to either something to jam the spout of the funnel into the filler hole, or as was common, an old radiator cap with a piece of tubing brazed into it & the funnel connected to it. The system was then filled until everything was full of coolant including all of the funnel & the bleeders opened to allow the coolant to fill the system. I have seen cases in the past where the funnel was left overnight and the car started a couple of times to allow the air to simply bubble back to its source in cases where bleeders were seized in or snapped off.
The heater control was always set in the hottest position to allow circulation through it otherwise no matter how well you bleed it, you'll have air trapped in the matrix which will cause problems either in the cars engine temp or the ability for the heaters to work.
You should love the car; I'm on a board where a couple of guys have 25s & they swear by them as a top motor car.
Alan S