Hi all, I’m hoping that you wonderful bunch can help me with an issue that I’m having. My recently acquired

Last edited by NorthernChap on 24th Sep 2025 10:51am. Edited 1 time in total

Just to add to this - the changeover valve that I bought isn’t a genuine LR item - it’s aftermarket but is the exact same unit that I used on my previous 405
Which worked perfectly. I guess there’s a small chance of this one being faulty? I tested the solenoid function before fitting and the engaged the solenoid as expected when receiving 12v

Did you unbolt and lift the reservoir tank up to bleed the system … it needs to sit about 10-15cm higher than its normal position for a proper bleed, not just parking it nose in the air. V8 or else ...

I didn’t, I have just been doing it in situ. I’ll give that a go at some stage today

The workshop manual (link in the wiki of this site ) has a description of how to do it. I think basically the tank needs to be raised in order to get it above the height of the rear aircon unit in the boot space . V8 or else ...

I found that when my changeover valve failed that one of the two pipes that run upto the EGR unit from the left hand side of the block (looking at the engine) was cold and the other hot. Maybe worth getting it up to temperature and popping the engine cover off and just checking both pipes are hot to discount the valve from the problem.

I'd already taken my valve off and tested it and the solenoid worked perfectly, re-assembled and still no heat. Popped a new genuine item on and heat restored, on stripping the old valve down I think the o rings swell and cause a flow restriction.

There is a specific bleed procedure for vehicles with 3 or 4 zone A/C (you have the extra A/C unit in the nearside rear 1/4) that involves diconnecting the coolant lines under the n/s/r wheel arch and purging air from this point, pretty sure it's in the wsm.

Edit: the aux FBH coolant pump is only used to pump the coolant when the FBH is running and the engine is off, once the FBH cuts out the pump stops - at least it does on mine! L405 SV Autobiography LWB SDV8, finished in Aston Martin China Grey by ETO division.