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Author: Subject: when delete cooling thermostat?
DavidIt

posted on 24/8/21 at 07:51 AM Reply With Quote
when delete cooling thermostat?

hi all,
i have a curiosity, i saw this kit for delete the thermostat in ebay:


Spoox kit

reading some posts, mostly from ford-related forums.. i understood this change will cause an overheating of the engine.
but if this company make and selll this kit... there must be a reason.
after some things, i think is related to have an electric waterpump .. maybe ecu controlled. but i've not found a clear answer.

anybody can explain me this apparent non-sense please?

thanks,
David

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G13BLocost

posted on 24/8/21 at 08:59 AM Reply With Quote
I think there is some confusion as to what a thermostat does. It does two things:
1. Restricts flow during warm-up to help the engine get to temperature faster
2. Creates a restriction in the water system to allow the main pump to create a 'pressure' in the system, increasing the boiling point of the water in the system.

Removing the thermostat will not neccisarily cause the system to overheat given a decent closed loop fan setup. I ran without one for years without issue. Just remember to not go over ~95degC, otherwise you will get boiling at hot spots in the engine.

Personally, I would suggest always running a 'stat and keeping your pressure cap in good condition. A good running water system is all part of a healthy running engine.

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Mr Whippy

posted on 24/8/21 at 09:20 PM Reply With Quote
The thermostat serves only one purpose and that is to divert coolant to the radiator to be cooled only when the engine is at the correct temperature and to then maintain that temperature by regulating the flow to a less or greater extent.

It's got nothing to do with building up pressure as that is a result of the expansion of the coolant when its heated inside a sealed system.

The only reason to delete it would be if the coolant flow to the radiator was regulated by something else, like an electronic pump controlled by the engines ECU monitoring the temperature sensor.

If the thermostat was removed from an engine with a normal engine driven water pump the engine will be over cooled and probably never reach operating temperature due to it flowing at full unrestricted capacity through the radiator.

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Westy1994

posted on 24/8/21 at 09:58 PM Reply With Quote
I am with Mr Whippy here.

I have tried the no stat with an electric pump, and it does work, but you will find it will take a long time to get up to temp from cold and you will have what I did, where the pump was active and pushing the water through the rad too fast because there is now no restriction in the circuit and this stops the water in the rad from radiating its heat away whilst still in the rad, so you end up with an engine running hotter than it did with a stat installed.

If you must remove the stat, simply break the bellows to create what would be seen if the stat was up to temp, then refit the stat.

All that said, I refitted mine as per what Ford recommended and I got a mate to build a far more intelligent controller for the pump rather than the basic one you get with these kits. Works a treat now and warms up fast - just as it should.





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G13BLocost

posted on 25/8/21 at 06:48 AM Reply With Quote
quote:
Originally posted by Mr Whippy
The thermostat serves only one purpose and that is to divert coolant to the radiator to be cooled only when the engine is at the correct temperature and to then maintain that temperature by regulating the flow to a less or greater extent.

It's got nothing to do with building up pressure as that is a result of the expansion of the coolant when its heated inside a sealed system.

The only reason to delete it would be if the coolant flow to the radiator was regulated by something else, like an electronic pump controlled by the engines ECU monitoring the temperature sensor.

If the thermostat was removed from an engine with a normal engine driven water pump the engine will be over cooled and probably never reach operating temperature due to it flowing at full unrestricted capacity through the radiator.


I guess that depends how you have your system plumbed. My system vents the cold side to atmosphere so its only the hot side, between the pump and thermostat, that builds pressure- due to both temperature and the pumps pressure head.

I don't think you can say 'it has nothing to do with building pressure'. Block off the thermostat and spin the pump... Pressure. I'll admit though I have seen some systems where the thermostat literally reroutes the water passed the radiator, in which case yes the only pressure was thermal.

All our cars are a little different

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adithorp

posted on 25/8/21 at 08:04 AM Reply With Quote
G13BLocost, you've got a cooling system open to atmosphere? No pressure cap? That's a system not used on cars since... well, pretty early last century. First with expansion in the radiator top tank and excess blowing out the cap and being lost, then later into overflow bottles to be sucked back as the system cooled and now in most cases to a pressurised expansion bottle. Exactly how does yours operate without boiling.

Whippys description is fairly accurate of how a "modern" car cooling system works, though westy1994, is also correct that the restriction caused by even an open 'stat is desirable (usually). Technically the pump does cause pressure in order to move water but it's more useful to consider it creating flow. With caps rated around 1bar blow off, thus raising the boiling point of the coolant above 100c this is the "pressure" most people refer to when considering a cooling system.

Even though temps will be measured as below boiling, areas within the water jacket (next to the cylinders) will be above that and without pressure will boil. So unpressurized systems of old, ran very cool to prevent that and subsequently fairly inefficiently. In most engines now, with the stat closed, the pump circulates water, via a bypass, within the block. Thus evening out block temps (especially during warm up) and lessening those hot spots. It certainly doesn't creat a measurable increase of the same order as expansion created pressure.





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coyoteboy

posted on 25/8/21 at 12:44 PM Reply With Quote
Stats are not designed to create pressure. They would work totally backwards if they were, as they'd create less pressure when the system was hotter!

Your system shouldn't be open to atmosphere, none of your engine cooling pathways were designed with ambient pressure cooling in mind, you're bound to be getting localised boiling.





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craig1410

posted on 25/8/21 at 01:17 PM Reply With Quote
One other thing to note is that removing the thermostat altogether can cause a change in the coolant flow through the thermostat housing and cylinder head which can result in hot spots or flow restrictions. It's a bit like the difference between having a smooth airflow into a carburettor by using a bell mouth ramp pipe or having the bare carb. The airflow (or coolant flow in the case of the cooling system) then has to take an abrupt turn which can restrict flow especially at high flow rates.

For this reason, on the old A-series mini engine it was commonplace to fit a sleeve if you removed the thermostat, or as someone else suggested above, just rip the mechanism out of the existing 'stat and refit it.

I agree that thermostats are not designed to create "pressure" but the flow through the 'stat will create a small amount of back pressure due to the restriction. This can help to ensure any localised boiling (small bubbles) are not created in the cylinder head as it will be at a marginally higher pressure than downstream of the 'stat. This might be important depending on where your bleed hose is located. If you have a bleed pipe at the top of the cylinder head then happy days but if the bleed pipe is coming off the radiator top hose then ideally you want any bubbles being collected there instead.

My advice is to always fit a thermostat but try to go for a good quality brand and if you're looking for a bit of extra power from the engine then by all means get a lower temp thermostat. Thermostats more often fail open then closed but if you're worried about it failing in the closed position then depending on the design of the 'stat you can sometimes drill a few holes which will ensure minimal flow even if it sticks closed.. That won't prevent overheating entirely but will give you more time to notice the temp increase before it overheats badly. It can also help avoid air locks.

HTH

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G13BLocost

posted on 25/8/21 at 03:22 PM Reply With Quote
I did not expect my comment to be so controversial, I think I worded myself poorly. Craig's reply is probably more helpful.

For reference, I have done a little diagram of my water system:

Description
Description


Having ran this in anger I don't appear have any cooling problems, and the datalogs also suggest this to be the case, so I am pretty happy with what I have. There appears to be no boil off of fluid and the pressure relief cap pumps excess pressure/fluid back to the header tank when the engine is hot, even at idle, so its a nice little controlled pressurised system within the engine itself between the pump and the thermostat/radiator.

In terms of "pressure" what I mean to say is, both the thermostat and radiator cause a restriction which the pump works against. This causes "back pressure". Flow, restriction and pressure all go hand in hand (in the same way Voltage, Current and Resistance go hand in hand). In my system that pressure in solely controlled by the pressure cap at the back of the engine that is connected to the top of the header tank.

Whether this is a modern or old style of cooling system, I couldn't comment. I chose to go with this as it is simple, and only requires a single reservoir; keeping the total system weight down.

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craig1410

posted on 25/8/21 at 03:26 PM Reply With Quote
quote:
Originally posted by G13BLocost
I did not expect my comment to be so controversial...



Welcome to the internet!

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adithorp

posted on 25/8/21 at 06:16 PM Reply With Quote
Define "run in anger" and for how long?

Sorry but if that header is open to atmosphere you don't have pressure in the system.... Unless we're going to also define the bottom of the system is at higher pressure than the top kit is but it's irrelevant)

Boiling will be happening around the cylinders, localised temps will soar and your head gasket won't survive long. Also as it's open, large amounts of water will be lost via evaporation on any extended run... Unless of course you've discovered something that every car engine designer has missed since at least the 1950's





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Oddified

posted on 25/8/21 at 08:18 PM Reply With Quote
As mentioned by several, never ever run without a pressurised system.

I'd normally run a lower temperature stat(80c - 82c ish), and a high flow version if available for the engine.

The only time i'd run without a stat is in an emergency if it was faulty/not working and i couldn't get a new one straight away.

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snapper

posted on 26/8/21 at 03:48 AM Reply With Quote
In your system the pressure cap is irrelevant as your header tank vents to atmosphere therefore your coolant will boil at 100c
If you have a pressurised system and depending on the pressure rating of your cap the coolant will not boil until 110c to 120c
Antifreeze also increases the boiling point of coolant.





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coyoteboy

posted on 26/8/21 at 09:08 AM Reply With Quote
quote:
Originally posted by G13BLocost
In terms of "pressure" what I mean to say is, both the thermostat and radiator cause a restriction which the pump works against. This causes "back pressure". Flow, restriction and pressure all go hand in hand (in the same way Voltage, Current and Resistance go hand in hand). In my system that pressure in solely controlled by the pressure cap at the back of the engine that is connected to the top of the header tank.

Whether this is a modern or old style of cooling system, I couldn't comment. I chose to go with this as it is simple, and only requires a single reservoir; keeping the total system weight down.


I'm well versed in fluid dynamics and thermodynamics, but your rad is designed to provide the lowest restriction possible and the stat will of course provide a fairly decent restriction at more closed points, but by design won't so much when open, but all of that won't raise system pressure by more than a couple of PSI above ambient. You can tell this because if you open your bleeder it won't fire out to 30ft, it'll squirt a few inches. The couple of PSI gives you maybe 4-5 deg extra headroom on boiling, and of course that's at full pump speed, as you come off the throttle and the revs drop, your system pressure drops and you flash boil. A pressurised cap gives you ~21 degrees margin on that and consistently, regardless of engine speed.

In your system as diagrammed, the cap does not control pressure (actually it does, it provides a ceiling in the section between pump and rad, but it would never realistically reach that ceiling because the system is open). Also, where does the fluid flow go when the stat is closed? I presume you have a bypass/recirc loop?

You don't need two reservoirs, you just need a pressurised reservoir. Not trying to be difficult, just trying to help you get to a better system! Deleting a stat is usually the kludge response to a poorly designed cooling system, or assuming that because someone sells something, there's a technical reason for using it.


[Edited on 26/8/21 by coyoteboy]





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mcerd1

posted on 26/8/21 at 11:52 AM Reply With Quote
quote:
Originally posted by coyoteboy
In your system as diagrammed, the cap does not control pressure

where does the fluid flow go when the stat is closed? I presume you have a bypass/recirc loop?

You don't need two reservoirs, you just need a pressurised reservoir.

^^ what he said - I think you'd have issues if its really open to atmospher (unless your header tank is 30ft in the air - that would give you some presure )


it is perfectly viable to have the expanssion tank open to the atmospher - but it needs to have a valve between it and the pressurised loop in the engine (ie. valve in the radiator cap) - but thats not wahts shown in your diagram


if you excuse the stupid text-to-speach - this video explains it quite clearly:
https://www.youtube.com/watch?v=y5p31F_dVJU

but its worth saying that some engines might plumb things a little differnet, but are functonally the same - and always have a presure cap / valve between all parts of the coolant loop and the atmospher
(eg. a pinto would tyically use the heater circuit as part of the flow path throught the head, so these use a bypass valve to just reciculate it directly when the heater valve is 'closed' a few extra pipes but teh coolant ends up in the same places )





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britishtrident

posted on 26/8/21 at 03:59 PM Reply With Quote
G13BLocost it might be better if you restrained from giving advice on this topic on this forum there are a lot of experience and knowledgeable builders.





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Mr Whippy

posted on 26/8/21 at 04:19 PM Reply With Quote
quote:
Originally posted by britishtrident
G13BLocost it might be better if you restrained from giving advice on this topic on this forum there are a lot of experience and knowledgeable builders.


I prefer everyone contributes, even if their knowledge is somewhat suspect. They'll soon be corrected and hopefully learn something in the process. Perhaps even spotting an issue with their car which they weren't aware off. I'd hate it if the only contributers to this site were self confessed "experts". We're all here to discuss and learn about something we're interested in, even if sometimes we come out with bollocks...

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G13BLocost

posted on 26/8/21 at 09:25 PM Reply With Quote
I am entirely open to being wrong on this subject! Lord knows it wouldn't be the first time.

It may simply be that:
A. My header tank is actually closed when I believed it to be vented to atmosphere through the cap all this time. Therefore the system is running at pressure.
B. I have simply got away with it. The system runs very cool, never going over 95degC. A good fan, a cool 'stat and very little pressure (PV=nRT).

I'll have a look at what I have at the weekend and see where it deviates from my mental model.

I certainly didn't mean to offend anyone. That said, some of your replies have been pretty unfriendly. We all have our areas of expertise and I am open to being schooled by a good clear well written statement. My experience is in suspension, dynamics, simulations, simulators and datalogging, having worked in this area for a number of years in Motorsport. But, I am no expert in cooling systems.

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Sam_68

posted on 27/8/21 at 09:55 AM Reply With Quote
quote:
Originally posted by G13BLocostThat said, some of your replies have been pretty unfriendly.


How's your dad doing these days?

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adithorp

posted on 27/8/21 at 11:24 AM Reply With Quote
quote:
Originally posted by G13BLocost
I certainly didn't mean to offend anyone. That said, some of your replies have been pretty unfriendly.


Apologies if that applies to my posts, it wasn't meant that way.





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Mr Whippy

posted on 27/8/21 at 04:09 PM Reply With Quote
quote:
Originally posted by G13BLocost

It may simply be that:
A. My header tank is actually closed when I believed it to be vented to atmosphere through the cap all this time. Therefore the system is running at pressure.
B. I have simply got away with it. The system runs very cool, never going over 95degC. A good fan, a cool 'stat and very little pressure (PV=nRT).

I'll have a look at what I have at the weekend and see where it deviates from my mental model.




Possibly, does the cap hiss if you take it off when hot? Certainly if your engine is well cooled it might never get really hot enough to boil. I drove my Bluebird around for years even towing a trailer with no fan fitted, it just didn't need it as it had a huge radiator. The only worry would be you getting stuck in traffic on a really hot day.

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G13BLocost

posted on 16/9/21 at 02:38 PM Reply With Quote
I never closed this off.

The long and short: I was being a silly boy. My expansion/header tank wasn't vented at all (I really thought it was) and the whole system was simply pressurised, the pressure cap doing little to nothing. In the name of having a reliable well cooled car I replumbed it as described by others above. The top of the system now bleeds to the top of the expansion tank and the pressure cap goes to a overflow bottle/tank. Easy-peasy.

I am only four weeks away from IVA so I am happy to have caught this now. Thank you to everyone who gave constructive feedback.

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indykid

posted on 17/9/21 at 08:22 AM Reply With Quote
Cunningham's law in action

To the OP, a fool and his money are soon parted. It's anodised aluminium. Race car, yo!





me? ambivalent? well, yes and no

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