Stag engine coolant flow diagrams

[GDPR]

Can anyone point me at any diagrams they know of showing detail and direction of coolant flow through the Triumph V8 please?

I would like to see them for both Mk 1 and 2 engines and 'stat open and closed conditions if possible as I have a Mk1 manifold on a Mk2 engine.

The Workshop manual shows pipework for both, but not actual flow, and I trawled through the tech articles on the website last night, but couldn't seem to find what I wanted - my fertile mind is cooking something up, possibly, and I won't sleep againuntil I know if it "has legs" - or maybe fins??

Thanks in anticipation

Russ

[DJT]

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Russ,

I had the same combination until recently. I changed to a Mk2 inlet manifold last year. The only difference I noticed was that the temp stayed a little more stable at speed. With the Mk1 there was a tendency for the temp to rise slightly, to a touch over mid way, at a sustained 70+ on a hot day. With the Mk2 manifold it stayedjust belowhalf. I have an 88-degree stat fitted.

Can't help with the flow diagrams, sorry.

Dave

[GDPR]

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Thanks Dave

That's pretty much my problem - I want to see if I can augment the block/inlet manifoldflow using a Vauxhall Omega electric heater pump - maybe I'll be lucky and find a Mk2 manifold instead.....


Besides, why use a simple solution if you have a REALLY complicated one available that is unproven and very likely to be a huge waste of time and money.....

I've been taking lessons in this from our government......


Russ

[alan_thomas]

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I am replacing all the inlet manifold and thermostat housing in my home made efi project and therefore I have studied the water flow thru the engine in some detail.

The flows are the same On both Mk1 and Mk11 with the except of the bypass circuit. No diagrams i am afraid but hear is a description.

The pump 'pulls' coolant from thebottom of the rad (hopefully after the rad has reduced the temp) and circulates it thru the engine block. Taking one cylinder bank as an example, (the other bank is identical) The waterways to the head are designed to drawn up the most water to frontmost head, less up to 3, 5 and 7. The water is drawn back thru the head and out thru the waterway under the inlet port of the rearmost cylinder. The very small waterway (about 3mm dia) alongsidethe frontmostinlet port does not contribute to the cooling of the cylinderhead but rather aids the warmup of the inlet manifold.

The water going thru therearmost inlet port circulates thru the inlet manifold,again warming the manifold and into the back of the thermostat housing.

With the engine cold and the thermostat closed there would be no coolant flow and hence the thermostat would not open before the water boiled in the head so to allow the hot water to reach the thermostat to allow it to open a bypass circuit is fitted.

The bypass circuit relies on the correct thermostat being fitted (one with a 'foot' !) this foot is lifted off the bypass outlet when the thermostat is closed and when the thermostat opens the bypass is blocked by the 'foot'. The bypass circuit has a direct hose connection to the pump thereby 'bypassing the rad' and hence not cooling the water.

A thermostat without a 'foot' does not close the bypass circuit and hence probably 40% of the coolant flow will bypass the rad - result = overheating

The heater circuit draws hot water from the rear of the LH bank (viewed from front) and returns it to the bypass circuit (the thinking is if the heater is 'on' the returning coolant has already been cooled.

After the thermostat opens the water is piped to thetop of the rad, hopefully cooled and exits thebottom of rad to return to the pump for another circuit.

The weak spot in the Stag system (and TR7, Sprint Saab etc)is the location of the pump, any coolant loss has the pump impeller spinning in hot air and the coolant flow stops or at best is severely reduced.



Now what other group of classic car owners is so keen to know their car's coolant circuit?

- Alan (Has your thermostat got a foot?)

[stustag]

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Alan I'm impressed by your knowledge of this subject and found this pic on the Googlenet! Which is the right thermostat?

Stuart

[GDPR]

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Alan - I'm really sorry, and will eat my own manifold if I'm found to be in error, but......I'm sure that you are fundamentally wrong with your view on the cooling system - I was a skilled mechanic for many years, and water pumps always drew from the lowest radiator connection. Car cooling systems are basically pump-assisted thermo-syphon so it would draw the coolest coolant possible, and that can only be from the lowest part of the radiator due to simple convection.

When I run my engine with the bung out of the rad, I'm sure that the coolant runs FROM the top hose to the rad - although it's fairly difficult to tell because of the long filler neck - this opposes your flow view.... and may affect any calculations you have made re your EFI cooling mods.

Are you sure?

The Stagonly gets into problems when the water level in the rad gets too lowsimply because the pump is so high in the water circuit....

My main concern is the flow in the upper parts of the engine where I can "tap" in with an external pump to assist the flow round the block.....

Russ


And Stuart - for mine with the Mk1 manifold, it's no 3

[redstag]

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This is the article that goes with the pics.

http://snic-braaapp.org/itech98.htm#TStat

The one on the left with a jiggle pin is correct for a Mk2.

Without a foot but still with a jiggle pin is correct for the earlier manifold.

Coolant definitely flows into the rad from the top hose.

Pete

[Kevin Garrod]

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I'm not going to take sides here, but I think Russ is right from memory the last time I was topping up my coolant I believe it was flowing into the rad as he describes. It would be easy enough to check, just not now!

In any case if the coolant level drops even a modest amount the pump would be left high and dry.

Since my recent rebuild my temp guage sits nicely around the E in TEMP, a good flushing seems to have helped, but we'll see how things go in the Summer.:?

[Bob Heritage]

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Russ

I have my engine in pieces at the moment and have taken some photos of the way I think it flows, I was doing this anyway because like you I am interested in a mechanical pump. I will download the pics when I get some spare time (because I have got to work out how first). Basically the water is drawn from the bottom of the rad to the pump, it then goes down into the block and goes to No's 1&2 cylinders where it it split and diverted into the cylinder jackets and the heads. The water links again at the rear of the inletmanifold and goes back to the thermostat or by-pass via the inlet manifold jacketand if stat is open to the top of the rad. The tapping at the rear of the nearside head goes to the heater and returns to the pump. The main weakness in the head gaskets is around No.6&8 cylinders where the tapping for the heater is, the temperature in the rear of No. 8 cylinder is greater than the corresponding 7 cylinder on the offside. I think it would be more balanced if another tapping was made in the rear of No. 7 of the head and 'T'd to No.8 before it goes to the heater. I also always keep the heater in the hot position to disperse heat from this area ( to screen in summer & out the open roof). Hope this helps and appreciate your views.

Bob

[mjheathcote]

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Yes defo the water pump draws water from the bottom of the rad, not the top hose.

How's your efi project progressing Alan?

Mines temporary on hold due to work commitments

[redstag]

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Hi Bob,

I've checked the temps onseveralcars and I think it was only one had heads with even temperatures.

All the others had higher temps in the RH head, around no.7 cylinder. Not sure why though and I didn't check which ones had the heater on (it was summer after all).

Pete

[Mark S]

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alan_thomas wrote:

The very small waterway (about 3mm dia) alongsidethe frontmostinlet port does not contribute to the cooling of the cylinderhead but rather aids the warmup of the inlet manifold.

Highest point of the water galleries in the heads, the holes are there to allowair to escape up into the manifold, especially when filling the system.

If your stat doesn't have a jiggle pin,it is good practice to drill a 2mm hole in the'flange', fit the stat with the hole at the top so that the air can bleed out when filling the system.

Mark.

[alan_thomas]

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kryten wrote:

Alan - I'm really sorry, and will eat my own manifold if I'm found to be in error, but......I'm sure that you are fundamentally wrong with your view on the cooling system - I was a skilled mechanic for many years, and water pumps always drew from the lowest radiator connection.
Russ

Russ, I agree you are right, I wrote the reply whilst eating my lunch at work and Although I read it back several times I missed that fundermental point. The main point I wanted to stress was the importance of the bypass circuit and the correct thermostat.

- Alan

[alan_thomas]

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mjheathcote wrote:

How's your efi project progressing Alan?

Mines temporary on hold due to work commitments

Michael, Yes, work is impacting my projectas well,but progress is being made. Now have the 'Toothed wheel' and Crank sensor arrangement sorted. The Megasquirt is built and tested. I have got the throttle body (from XJ40) and made up a linkage. I got a new Bosch hi pressure fuel pump from Ebay really cheap (nobody else bid!) but need to weld up a swirlpot to ensure a continous fuel supply.

I decided I needed my own machining facilities and have managed to buy a cheap milling m/c and Myford lathe and have started, after rebuilding the lathe,machining the inlet headers. The major part left is fabricating a Plenum.

So progress is good but I don't think it will be finished before this years 'season' so I will replace the std inlet manifold and use the car, probably with the Megasquirt wasted sparkignition this summer and fit the injection next winter.

- Alan

[mad cyclist]

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i have decided you are all too clever for me, making plenium chambers ect, I feel very lacking!!:?