XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Looping Idle speed

Old 05-21-2014, 09:57 AM
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Default Looping Idle speed

Hi guys i need some help.

I brought a 1989 5.3 V12 xjs, when i start her up the idle speed loops until the engine warms up and then it seems to be fine. How can i resolve this? Also this may seem a really stupid question but where do i add the water?
Old 05-21-2014, 02:50 PM
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your AAV is playing up , this is a wax filled bulb mounted at the back of the left water rail under the throttle linkage , it regulated extra air for warm up ,

the car should rev at about 1200 , and gradually drop to about 750 revs

the wax bulb detects the water temp and gradually closes a sliding valve , this is playing up

removal and a clean could help , or a replacement might be the only answer

no need to drain water, but you will need a new gasket for the AAV

water is added by using the two rad caps,

remove both , fill from the front engine one until the water comes out of the one on the wing ( expansion tank ) , then fit the cap to the one on the wing, then continue to fill from the front until its up to the cap ,

fit cap , run engine for a few mins, when cool remove front cap and top up as required

hope this helps


Last edited by Brake buster; 05-21-2014 at 02:53 PM.
Old 05-22-2014, 07:44 AM
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Hi thank you so much for your help :-)
Old 05-22-2014, 07:49 AM
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Just to butt in, I also use the bleed valve at the top of the radiator (left hand side when looking at it from the seat); it's a hex nut usually recessed slightly.
Top up until water starts to come out of here, close it and then the wing tank and the centre one.
Some people recommend parking on a slope with the front facing uphill to get the maximum amount of air out of the system.
I think that the correct fill level is 4" down the centre one.

Last edited by Steve M; 05-22-2014 at 07:50 AM. Reason: Forgot a bit
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