Serp coolant circuit - inlet manifold

[Pupp]

Still battling very odd cooling issues after doing the full heater rail delete (seems like air-locking in the manifold or heads with some pretty vicious and swift temperature spiking and coolant venting from expansion tank after being expelled from the swirl pot. Now wondering if the thermostat bypass has been compromised by my changes...

So, anyone able to say for sure whether the water chamber behind the rectangular boss hanging off the bottom of the serp manifold is the same void the side outlet on the top drivers side exits from (pic is not a Tiv one as ours are blanked where the outlet on this one is, with a temp sender in the bung)? I should have specifically checked when doing the mod but overlooked it and now just reality checking in case a schoolboy error has been made.

Just for context, the heater loop now feeds off the rear face of that boss and returns into the top of the water pump inlet instead of into the bottom hose swan neck. If the chamber is common to both points, then not the issue but just wondering if there is some separation and internal bypass routing I was unaware of ...

[Sardonicus]

Gary so long as you have coolant bypass flowing and circulating coolant past the rear of the stat you should have no issues with your loop/bypass mod where does your Turbo take and dump its coolant relative to your plumbing ? these may help your curiosity ............................................... ... ... ...

Edited by Sardonicus on Wednesday 14th June 11:23

[Pupp]

Simon, thanks... those pics are very helpful.
Turbo is teed into top hose just before rad on one side and the other into the swan neck from the bottom hose (ie the tee the heater loop used to use before dropping it into top of water pump).
This has really taken so much time and head scratching now; only place I can go with it is to pull the manifold and remake the compression joint into back of the boss... there must be a leak path there.
Oh well, sensible car for LM... climate control and fuel savings so not all bad!

[Pupp]

Ok - didn't resolve in time for Le Mans so had to put up with nearly 50mpg and climate control rather than risk the Tiv (it would have died in the heat for sure) - But maybe have a workaround if not a cure (so at least an understanding of what is happening hopefully).

Thinking, as mentioned on the heater pipes thread, that the various 'uphill' exits from the manifold are not there by accident, and serve to assist degassing (which is a shame as all exits on mine are now horizontal), I have tonight teed the redundant plenum heater spur (usually blanked with a plugged hose) into the expansion pot feed from the top of the swirl pot. Not run yet so jury's out but can say filling was much quicker as the air just peed out and, perhaps tellingly, the expansion tank level also equalised levels for so long as the cap was off, whereas it never moved before - am thinking big airlocks in the heads/manifold behind the thermostat with the heater pipe delete combined with front exit JE thermostat housing; now relieved by allowing a path through to the swirl pot.

Pub was calling tonight so didn't road test but will tomorrow. Next step will be to drill the thermostat if this proves ineffective (positive vibes so far)

[Sardonicus]

Pupp said:

Ok - didn't resolve in time for Le Mans so had to put up with nearly 50mpg and climate control rather than risk the Tiv (it would have died in the heat for sure) - But maybe have a workaround if not a cure (so at least an understanding of what is happening hopefully).

Thinking, as mentioned on the heater pipes thread, that the various 'uphill' exits from the manifold are not there by accident, and serve to assist degassing (which is a shame as all exits on mine are now horizontal), I have tonight teed the redundant plenum heater spur (usually blanked with a plugged hose) into the expansion pot feed from the top of the swirl pot. Not run yet so jury's out but can say filling was much quicker as the air just peed out and, perhaps tellingly, the expansion tank level also equalised levels for so long as the cap was off, whereas it never moved before - am thinking big airlocks in the heads/manifold behind the thermostat with the heater pipe delete combined with front exit JE thermostat housing; now relieved by allowing a path through to the swirl pot.

Pub was calling tonight so didn't road test but will tomorrow. Next step will be to drill the thermostat if this proves ineffective (positive vibes so far)

Good call Gary my block is vented at the front and rear so I also have the easy filling no airlocks etc now your bypassing the stat slightly like you have you could say it slows warming but being such a small bypass that not been noticeable IMO even with both my banks vented I did this because the rear of the block will have almost stagnant coolant and I like things moving all the best

[Pupp]

Took it out this morning and still doing odd things... from cold it hit 110+ before falling and stabilising around a 79 to 86 cycle (will change the thermostat just in case but...), then seemed to behave fine with no gurgling on key off when I stopped to buy a paper, and no coolant ejection.... staying the same for another half hour tootling about. Then it chucked a load out when I got home.


Simon - on yours, the outlets on the rear of the manifold (where usually blanked), have you just linked those together to allow equalisation or are they feeding elsewhere?

[carsy]

This is how mine behaved Gary when i changed to the serp front end, although it never chucked coolant out.

I figured the thermostat wasnt opening until very late, (well into the red infact i would switch off), due to it sitting in air as when i took it out to test it, it behaved fine repeatedly and was relatively new anyway.

As i said i removed the toggle pin thinking it was hindering the bleeding process and also drilled the hole out a few more mm bigger. It has behaved fine ever since, so for me the toggle pin was for some reason keeping the thermostat in air rather than water.

Just a thought !

[Pupp]

It's air-locking Ian; I'm sure of it... I'm going to try substituting a line off the original heater outlet for the plenum heater but am thinking the swirlpot top might not be the best place to dump it to.... anyone know where the Rangie/Disco plenum heaters returned to?

Then will drill the stat/de-jiggle it

It would be very easy to conclude there is an air leak in the 'new' fitting under the manifold but that went in tight, true and sealed I am sure, so am clinging to it being a hose geometery/config issue.... so not going to put it back to OEM!

[carsy]

On a pre serp the plenum heater return feeds into the heater return pipe which runs under the inlet manifold and goes into the water pump. The pick up for it into this pipe is just in front of thermostat housing.

[Pupp]

So knew you were going to post that... bloody heater pipes again

[Sardonicus]

Pupp said:

Took it out this morning and still doing odd things... from cold it hit 110+ before falling and stabilising around a 79 to 86 cycle (will change the thermostat just in case but...), then seemed to behave fine with no gurgling on key off when I stopped to buy a paper, and no coolant ejection.... staying the same for another half hour tootling about. Then it chucked a load out when I got home.


Simon - on yours, the outlets on the rear of the manifold (where usually blanked), have you just linked those together to allow equalisation or are they feeding elsewhere?

Both T left and right banks before feeding into the swirl pot Gary, and Carsy that opening out the stat bleed/jiggle pin port does no harm and on these cars is not detrimental to the warm up and aids quicker bleeding IMO I have only ever used a OE Wahler stat no mods out of curiosity

[Steve_D]

carsy said:

On a pre serp the plenum heater return feeds into the heater return pipe which runs under the inlet manifold and goes into the water pump. The pick up for it into this pipe is just in front of thermostat housing.

Your bleed can return to the heater return pipe quite happily despite it being lower than the point you are trying to bleed. You are trying to bleed off any air/steam trapped in the head which will likely accumulate after shutdown. When you start from cold the pump will be trying to pump water into the block but it can't escape into the system because the stat is closed but it will escape through your bleed and into the pump inlet.

Steve

[Pupp]

What I'm really not getting my head around is how, even with what is effecrively an 8mm bypass now, I am seeing 110 degrees before the stat opens (this on gauge and logged by the ECU so confirmed by 2 sensors) yet once it has opened first time, it then cycles perfectly normally while running...

I know I'm going to kick myself eventually

[Sardonicus]

Gary just try one of these 1st, otherwise you may just go mad got to be worth a try http://www.ebay.co.uk/itm/Thermostat-TVR-Chimaera-...

[bobfather]

Pupp said:

What I'm really not getting my head around is how, even with what is effecrively an 8mm bypass now, I am seeing 110 degrees before the stat opens (this on gauge and logged by the ECU so confirmed by 2 sensors) yet once it has opened first time, it then cycles perfectly normally while running...

I know I'm going to kick myself eventually

That temperature does appear to be high but you should bear in mind that the temperature of the coolant isn't even throughout the system, in fact there will be huge differences in temperature between different locations in the system. Obviously the highest temperatures will be in the channels around the heads as this is where the heat is generated. The thermostat may not be seeing the same temperature as the ECU sender.

[Sardonicus]

bobfather said:

Pupp said:

What I'm really not getting my head around is how, even with what is effecrively an 8mm bypass now, I am seeing 110 degrees before the stat opens (this on gauge and logged by the ECU so confirmed by 2 sensors) yet once it has opened first time, it then cycles perfectly normally while running...

I know I'm going to kick myself eventually

That temperature does appear to be high but you should bear in mind that the temperature of the coolant isn't even throughout the system, in fact there will be huge differences in temperature between different locations in the system. Obviously the highest temperatures will be in the channels around the heads as this is where the heat is generated. The thermostat may not be seeing the same temperature as the ECU sender.

Why wouldn't it? its adjacent

[Pupp]

Exactly... they are all in the same volume... or should be.

Thanks for the link Simon... problem is my housing dictates a small aperture stat

[carsy]

Why dont you try running with the stat removed , temporarily obviously, and see if the temps then fluctuate and also if it still dumps coolant.

This might help point towards stat issue or pipe configuration.

[Sardonicus]

Pupp said:

Exactly... they are all in the same volume... or should be.

Thanks for the link Simon... problem is my housing dictates a small aperture stat

sorry Gary forgot you run a remote housing scrub my suggested link then, still be inclined to try a new stat with the small hole mod however like Carsy mentioned when doing this previously I have just done a 3/5mm mellows the temp differential too

Edited by Sardonicus on Sunday 25th June 14:47

[Pupp]

Right.... stat out and checked on the stove.. opens on the nose at 74deg.
Jiggle pin removed and bypass circuit removed... only the slightest expulsion of coolant and normal behaviour APART from 118 degrees logged before stat opened.
Now sure it's airlocking behind stat... closely examining the JE front exit housing I'm using shows the jiggle pin hole sits very very close to the casting... sl close I'm wondering if it can even be at all effective.
Next move will be to run the bypass loop ftom the heater side exit... that is noticeably higher than the plenum heater port.
If that doesn't sort it, I'm breaking the bugger