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[Big_Roger]

OK, spurred on the by findings of MV6Man on vacuum tanks etc earlier today, I was determined to sus out problem of hot water constantly circulating through the heater matrix on my car, even with cooling on.

I borrowed a vacuum gauge, and removed vac pipe from HBV and connected it to the gauge. Started up and I have 17mm Hg on valve.
It switches between 0 and 17mm Hg as I alter temperature setting on the Climate control from about 19 deg to 23 deg C so no problem with Climate control, although I did expect it to modulate to vary the amount of water through the valve, I guess it's about right if only controlled by a solenoid valve.

From this I presume that the HBV is stuck in the heater flow position, and have ordered a replacement from dealer.

What I would like to know from all you people that have replaced these valves, in case any previous owner has fitted it incorrectly, what are the correct hose connections to the valve ??

My system is the version with the additional heater circulating pump under the cooling sys header / filler tank.

Roger

[Kevin Wood]

I don't believe it's supposed to modulate, it's an on/off valve. Temperature control is achieved by a mixer flap that directs more or less air through the matrix. As you say, sounds like your system is working up  to the valve.

IIRC, the single pipe connection on one side of the valve goes to the feed from the coolant bridge. Of the two the other side, the lower of these is a bypass connection to the transfer pipe which goes into the back of the block. The upper pipe is the flow to the matrix via the electric pump.

Kevin

[jonathanh]

I don't believe it's supposed to modulate, it's an on/off valve. Temperature control is achieved by a mixer flap that directs more or less air through the matrix. As you say, sounds like your system is working up  to the valve.

IIRC, the single pipe connection on one side of the valve goes to the feed from the coolant bridge. Of the two the other side, the lower of these is a bypass connection to the transfer pipe which goes into the back of the block. The upper pipe is the flow to the matrix via the electric pump.

Kevin

Yep - it's a straight on/off valve: no modulation at all.  

[Marks DTM Calib]

Yep, the single feed to the bypass valve connects via the helter skelter type curly pipe to the coolant bridge.

The lower outlet from the valve connects to a T section type hose, one end of which connects to the coolant transfer pipe that runs around the 1-3-5 head and the final end has a quick release connector to the bulk head heater matrix feed..

The final pipe comes from the upper outlet of the valve, travels to the additional pump and then back to the upper quick release connection point on the bulk head heater matrix feed.

[Kevin Wood]

BTW: when I took my old HBV off (changed it while doing LPG plumbing) I noticed that it doesn't appear to totally block either port when it operates, so it may be that the matrix pipes won't run totally cool even with a working HBV. Either that or mine was knackered, although I've noticed no vast increase in cooling efficiency.

Kevin

[Big_Roger]

Hi all,
Thanks for the info folks, that's the way it is connected, so must be duff HBV

Roger

[MV6Man]

I been studying this HBV operation today...
Iīve found that if i drive like 20 minutes with A/C on low, my heater matrix is pretty hot when shutting my engine.
I suppose that it shouldnīt be like that if that HBV works perfectly?

Maybe thereīs something blocking itīs movement or itīs jammed totally. I have that additional pump too.

That heater matrix is pretty easy to check, left end of matrix is located near where centre console (side) and dashboard meets.
There should a rubber that is pretty much same size as matrix.
Just put your hand to it and you can feel it...