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MG MGB GT V8 Factory Originals Technical - Water Pipe Plumbing
|I am using the new type distributor-less front cover which has no input for one of the heater pipes in its water pump. This is being used in conjunction with an earlier type FI system, which has two pipes running under the FI manifold, one off which is straight through and the other taps in and out of the manifold water jacket. |
1. I presume the older type water pump with the extra input is for the heater matrix return (IE the straight through pipe), and can be replaced by tapping into the bottom hose instead!
2. Where does the forward feed of the second pipe go? The rear half of this pipe, which outputs from under the manifold I presume is the matrix feed!
I never saw the original set-up, so any information would be much appreciated.
Can't quite picture your set-up but with the SD1 type front cover and P6 water pump I would expect to see
1) a hose from the water pump inlet, connecting to a tube under the manifold, connecting to a hose to the heater matrix - this is the heater return plumbing
2) an outlet somewhere on the inlet manifold connecting to a heater on/off valve connected to the matrix - this is the heater feed. On my EFI manifold the outlet is at the front righthand side. On my car this goes via a pipe beside the righthand rocker cover.
Yes the heater return feed could tee into the bottom hose if you don't have a connection point on the pump itself.
Thanks for confirming the plumbing for the return pipe.
The outlet exiting from under the inlet manifold has two outputs one forward and one backwards. The rearwards one would be the tidiest to connect to the heater on/off valve connected to the matrix.
Does anyone know where the forward one should be plumbed, or can it be blanked off.
|I also don't have the outlet which you refer to on your water-pump and I have never understood why. My forward hose is merely blanked off and the system seems to work well - except that unless I have the heater water flow turned on just a tad, I seem to get what are probably steam traps developing which result in occasional temperature rises - on the guauge, anyway to over 110c. I find that cracking the heater tap slightly seems to prevent this happening although I then have the problem of heated air entering the cab in summer.|
Paul Hunt has seen this problem on my car and he agrees about the cause.
I have just managed to find some plastic Y pieces for insertion into the heater hoses to allow me to by pass the heater matrix when the heater is switched off. I shall be installing these next week and hopefully this will allow me to close off the heater completely and yet to avoid the superheating problem.
The Y pieces apparently come from the heater system of Ford Escorts. I could get you better details of you need them.
|To clarify the above, Both Paul Hunt and I came to the conlusion that completing the circuit into the water pump outlet would allow steam traps to be avoided in some way and an open heater circuit would not then be necessary.|
|With a pre-serpentine engine there is an outlet at the front left of the manifold that is connected by a hose to the back of the water pump. It is a thermostat bypass that ensures that water still circulates (albeit slowly) through the engine when the thermostat is closed. Without it you would get localised hot spots within the engine leading to steam traps as Marc says. Turning on the heater effectively creates an alternative thermostat bypass. Serpentine engines dont need this bypass pipe because the bypass is internal to the water pump (at least thats what I read somewhere). My serpentine engine also had a small hole in the the thermostat itself that you have to position uppermost to let steam pass into the top hose. You can make out the bypass pipe if you look closely at the engine diagram on my website.|
|Having looked at the diagram myself - the bypass hose actually connects to the back of the SD1 timing cover and thus through to the pump. Link to the website is on my first posting above.|
Like your website. Ive got it now.
I will fit a heater matrix bypass, so I will pickup some "y" pieces next time I am up the scrap yard.
This thread was discussed between 12/06/2003 and 13/06/2003
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