SpitFire6 Posted January 8 Report Share Posted January 8 Hi, Does the GT6 water pump housing have a cast-in port to allow coolant to bypass the cylinder head? Cheers, Iain. Link to comment Share on other sites More sharing options...
johny Posted January 8 Report Share Posted January 8 I looked into this as the manual drawing is confusing. Unlike later designs the flow through the head is held back by the thermostat until hot enough to open it so when cold the only flow is through the manifold (and heater if selected) and back to the pump... Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 9 Author Report Share Posted January 9 Hi Johny, my bypass is from the rear of the head through the heater to the suction point of the pump. It can never be throttled. I never saw a need to be able to control flow through the heater so I deleted the valve and control decades ago. I use the cabin heater blower-fan to control heat. So the pump housing has a port between the inlet & outlet? Cheers, iain. Link to comment Share on other sites More sharing options...
johny Posted January 9 Report Share Posted January 9 No, on mine (MK1 Vitesse) the water comes into the pump suction from the radiator and heater/manifold return and leaves through a port into the head and also a connection via hose to the manifold/heater. From the former it passes through the head/block it comes back to the housing where its stopped by the thermostat until it opens. Yours is obviously slightly different as it allows some circulation through the engine while warming up... Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 10 Author Report Share Posted January 10 Hi Johny, Looks like I will have to remove the thermostat to check there is no port. No big deal. If there is a port it is getting plugged! Cheers, Iain. Link to comment Share on other sites More sharing options...
johny Posted January 10 Report Share Posted January 10 Yes the issue is complicated by the fact that later cars (Dolomite 1850 etc) have double acting thermostats so that coolant is circulated round the engine during warm up and then switched over to the radiator. Even so I cant see why there would be a port between pump inlet and outlet as this would just be a waste - its minimum flow is always maintained using the path through the manifold.... Link to comment Share on other sites More sharing options...
Gully Posted January 10 Report Share Posted January 10 Does this help? Shows the head ports below the thermostat. Gully 1 Link to comment Share on other sites More sharing options...
johny Posted January 10 Report Share Posted January 10 On my Vitesse I found the diagram in the manual to be wrong. Heres the housing with the left port discharging from the pump into the cylinder head so that it returns to the right hand port where it enters the chamber below the thermostat. Here its held back until the thermostat opens although some can flow out through the small pipe connection to the manifold and heater. The pump suction at the bottom has tow entries, the main from the radiator and the other is the return from the manifold and heater. I think this arrangement is entirely logical as with the thermostat closed theres a small flow through the engine that is used to warm the manifold as soon as possible to reduce choke usage while also warming the thermostat to ensure it opens correctly... 1 Link to comment Share on other sites More sharing options...
Colin Lindsay Posted January 10 Report Share Posted January 10 (edited) I've just been sandblasting one of those housings so had to nip out and get some quite dusty photos. The water pump rotation propels the coolant into the chamber on the right (front view) along the head and back out into the housing, where it drains through a small hole back into the system again. Once the thermostat opens it also exits via the pipe in the housing, through the thermostat and so through the radiator, and is drawn back up from the radiator bottom hose to recirculate again. I assume the small hole is to restrict the flow to make sure the majority goes round the radiator. The heater circuit works off the long pipe and the hose take-off but the flow there too is controlled by the thermostat ie car / head warms up first before anyone else gets heat. Edited January 10 by Colin Lindsay trying to work out left from right 1 Link to comment Share on other sites More sharing options...
johny Posted January 10 Report Share Posted January 10 (edited) 26 minutes ago, Colin Lindsay said: The water pump rotation propels the coolant into the chamber on the right (front view) along the head and back out into the housing, where it drains through a small hole back into the system again. Once the thermostat opens it also exits via the pipe in the housing, through the thermostat and so through the radiator, and is drawn back up from the radiator bottom hose to recirculate again. I assume the small hole is to restrict the flow to make sure the majority goes round the radiator. The heater circuit works off the long pipe and the hose take-off but the flow there too is controlled by the thermostat ie car / head warms up first before anyone else gets heat. Thanks Colin. I see now that little hole is for some other purpose - does it go to the temperature sender? Edited January 10 by johny Link to comment Share on other sites More sharing options...
johny Posted January 10 Report Share Posted January 10 Thinking about it I reckon the hole goes to the pump suction so that coolant circulates through the engine even with the thermostat closed. On mine the manifold/heater does the same thing but I suppose this gives an added measure of security.... Link to comment Share on other sites More sharing options...
DanMi Posted January 10 Report Share Posted January 10 Don't forget that early cars such as MK1 spitfire don't have a heated manifold and the heater was an optional extra, so that hole is definitely needed then to get the water moving before the thermostat opens. 1 Link to comment Share on other sites More sharing options...
Colin Lindsay Posted January 10 Report Share Posted January 10 2 hours ago, johny said: Thanks Colin. I see now that little hole is for some other purpose - does it go to the temperature sender? No, it just drains back into the main system; sender unit sits above. I suspect it's the same as the oil circulation; only a percentage goes round at any one time and the rest drains back. Link to comment Share on other sites More sharing options...
AidanT Posted January 10 Report Share Posted January 10 Those pictures make me sure I need to get mine cleaned out! Aidan Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 10 Author Report Share Posted January 10 Hi all, Yes, that is the little port I thought I had noticed last time I changed the housing. I am not sure what it does when the thermostat is closed but when the stat is open it must allow some cooled coolant to bypass the head/heater? Cheers, Iain. Link to comment Share on other sites More sharing options...
johny Posted January 10 Report Share Posted January 10 Dont think so Iain, what would be the purpose? I think the flow is a bypass of the thermostat/radiator and it goes from engine coolant discharge directly to pump intake (the centre area behind the impellor)... 1 Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 11 Author Report Share Posted January 11 Hi Jonny, the pump inlet/intake is only available on the bottom hose & the fitting on the side that has the pipe connection. Apart from bypassing the head, maybe the port is an air bleed? Cheers, Iain. Link to comment Share on other sites More sharing options...
johny Posted January 11 Report Share Posted January 11 Isnt that the hole Ive marked here? If so it looks as if it could go directly into the pump suction chamber under the thumb shown... Link to comment Share on other sites More sharing options...
DanMi Posted January 11 Report Share Posted January 11 Water needs to be moving even before the thermostat opens to prevent boiling at the hottest places, so there must be a route for the circulation, which this hole would allow. Not all Triumphs have heated manifolds and the heater can be off, yet this is a common design/part. 2 Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 11 Author Report Share Posted January 11 13 hours ago, johny said: Isnt that the hole Ive marked here? If so it looks as if it could go directly into the pump suction chamber under the thumb shown... Hi Johny, Are there two ports in the housing? One at the top & one at the bottom as shown in your picture? Thanks, Iain Link to comment Share on other sites More sharing options...
johny Posted January 11 Report Share Posted January 11 Think all the photos so far show just one which is viewed looking down in through the thermostat housing or from the back through the engine return port where the same hole is more difficult to see as indicated by my arrow. If we had one Im 90% certain a piece of wire pushed down through the hole would appear in the centre recess of the impellor well (the suction inlet) as shown here... Link to comment Share on other sites More sharing options...
Colin Lindsay Posted January 11 Report Share Posted January 11 You had to ask... I knew that bit of green wire would come in handy some day. That's a proper GT6 housing, I think my others are Herald but exactly the same principle. 1 Link to comment Share on other sites More sharing options...
johny Posted January 11 Report Share Posted January 11 Thanks again Colin and blimey its true! Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 11 Author Report Share Posted January 11 Hi Johny, et al. Thanks. So the small single port/tube connects the outlet from the head back to the suction side of the pump. If there is never an external flow out of the head, circulation is ensured through the head via this port? Cheers, Iain. Link to comment Share on other sites More sharing options...
johny Posted January 11 Report Share Posted January 11 Correct and its good news for me as Ive installed an isolating valve in the external hose that goes to the manifold and heater. My idea was that in hot climates theres no need for either so instead I could maximise flow through the radiator for improved cooling. Now with the port I can see that on start up the pump and engine still has a minimum flow👍 1 Link to comment Share on other sites More sharing options...
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