The Triumph Dolomite Club - Discussion Forum

Has anyone got a TDC brass by-pass tube replacement for the EWP conversion they can either take detailed & accurate dimensions of or lend to the club please?

Timing error! I have one and had it out last summer to replace leaking seals! But it's back in the engine now!

If all else fails, i'll pull it again, but i'd rather not!

Steve

Carledo wrote: ↑Thu Jan 21, 2021 4:42 pm Timing error! I have one and had it out last summer to replace leaking seals! But it's back in the engine now!

If all else fails, i'll pull it again, but i'd rather not!

I didn't know there was such an item, Steve.
I used core plugs.

Using core plugs is a win, win in my opinion because
you don't have to contend with trying to seal the bypass pipe anymore and also
it is possible to mount the inlet manifold using studs, making gasket alignment precise.



Ian.

I have a NOS OE tube for the outside dimensions, but would be guessing at the size of the hole...

Good point. Yes they will be the same outside dims. and the tapped hole through the middle doesn't really matter what size it is as it's just for bleeding the air out.

If the size of the hole doesn't matter, then why can't the original part be retained?

WEEEEELLLLLL, looking at it as an engineer and considering the design of the waterflow through the engine, I think it does serve a purpose as is.

If you merely blank the holes as Ian suggests, it will work fine, but may be inclined to airlock in the empty pump housing, especially if the heater return is correctly redeployed to below the EWP, the bleed hole in the mod pipe negates that.

Because the DC pump is designed to run without a thermostat, leaving the full bore bypass in place will allow too much coolant to bypass all the time reducing the amount of cooler water circulating in the block with potentially disastrous results.

So the pinholed bypass is the best available solution. The car I have it fitted to seems to function very well, without remote stat or any other clobber, the engine warms quickly (it has electronic control module for the pump/fan) and the heater works passably well.

The only better solution I can come up with, off the top of my head, is to blank the bypass entirely and fit a bleed screw to the old pump housing that would only be used (or needed) when draining/refilling the cooling system. The potential downside is that it would be difficult to locate as the housing is in a rather inaccessible place, most of the top surface of it especially so. And if you didn't know it was there, you're back to airlocks........

Steve

Edit, if an approximation will do, i'd say the vent hole in mine is 3-4mm dia. I suspect you could work it out from Marts pic, ie size of hole as a percentage of (known) overall diameter of pipe.

So, despite the ewp being designed to work without the stat, what problem would there be in retaining the stat and the OE bypass pipe? The foot of the stat blocks the hole as required...but water pressure created by the pump circulates as normal....

Carledo wrote: ↑Fri Jan 22, 2021 9:50 pm If you merely blank the holes as Ian suggests, it will work fine, but may be inclined to airlock in the empty pump housing, especially if the heater return is correctly redeployed to below the EWP, the bleed hole in the mod pipe negates that.

An interesting point you have raised Steve,
but irrelevant to my installation because I fill the cooling system through the header tank,
with said header tank plumbed into the bottom hose.



Ian.

xvivalve wrote: ↑Sat Jan 23, 2021 7:35 am So, despite the ewp being designed to work without the stat, what problem would there be in retaining the stat and the OE bypass pipe? The foot of the stat blocks the hole as required...but water pressure created by the pump circulates as normal....

You will encounter two problems doing that
No. 1 you will have heat from the heater because the EWP will push the coolant away from the pump housing and more seriously
No.2 when the thermostat is closed there will be no flow through the radiator, which means no flow into the pump
(it will still rotate but obviously has nothing to pump).


Stewart electric coolant pumps are designed to work with a thermostat.



Ian.

sprint95m wrote: ↑Sat Jan 23, 2021 11:16 am

Carledo wrote: ↑Fri Jan 22, 2021 9:50 pm If you merely blank the holes as Ian suggests, it will work fine, but may be inclined to airlock in the empty pump housing, especially if the heater return is correctly redeployed to below the EWP, the bleed hole in the mod pipe negates that.

An interesting point you have raised Steve,
but irrelevant to my installation because I fill the cooling system through the header tank,
with said header tank plumbed into the bottom hose.

Ian.

I envisaged filling into the bottom hose. But picture it filling, the water will rise slowly up the bottom hose (and rad) and through the water pump, at a certain point the level will reach the lower side of of the old pump housing and start filling the block. As it fills, the water level in the old pump housing rises, but the inlet into the block is lower than hose entry and maybe an inch or so lower than the bottom face of the waterpump housing. when the water level reaches the top of the block entry hole you will get a large bubble of air trapped in the old pump housing with nowhere to go. There's no stat fitted so the block will continue to fill and up to the head but the air bubble is still trapped. It can't escape through the blocked off bypass or the blocked off heater return. Once the pump starts running it may be dispersed, or it may not (my theoretical fluid dynamics isn't good enough to work that out) It COULD all solve itself, but bearing in mind the slant's propensity to react badly to overheating, i'd rather not risk it, particularly since a tailormade solution is available in the form of the modified bypass pipe.

Steve

I understand what you are getting at Steve
but what of the start up procedure where the cap is removed from the header tank?


Thanks

Ian

sprint95m wrote: ↑Sat Jan 23, 2021 10:07 pm I understand what you are getting at Steve
but what of the start up procedure where the cap is removed from the header tank?


Thanks

Ian

Leaving the rad cap off the header alone wouldn't make any difference. I always leave the cap off any car (not just Dolomites) that I have drained and refilled until the engine has run long enough for the stat to open and the coolant level to stabilise, then I top it up and fit the cap. I'm also still inclined to remove the original filler plug from the stat housing when filling to improve self bleeding of the system. But that doesn't get round the pump housing airlock possibility either. Only a running pump with enough power to push the trapped air into the block and thence upwards through the stat housing and into the header via the thin pipe will do that. On my controlled EWP system the pump doesn't run at all on startup and only gives 10-30 second pulses during warmup, so it's doubtful if the pump would run enough until the motor is pretty hot. Which sounds a bit risky to me!

Maybe i'm being overcautious, I call it outwitting Murphy's Law! 50 years in this business has given me a sensitivity to airlocks on refilling, I can tell from the way the water level in the header behaves on warmup, when to suspect one. But I am very aware that not everyone has my wealth of experience and could make an expensive mistake through no real fault of their own. So when I design or mod something, I try to make it as foolproof (or even squaddie proof, a much higher standard) as possible! Someone MUST agree with me, or the modified bypass pipe wouldn't exist!

Steve