Coolant catch tank

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stu60
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Re: Coolant catch tank

Post by stu60 » Sat Aug 10, 2019 2:36 pm

Hi,
I was initially confused but now (I think) understand.

- Basic system as fitted to HAwk using Gerry's aluminium cylindrical expansion tank. This has a pressurised rad cap on it. It should be filled to half way up the cylindrical tank to allow for coolant expansion when it heats up. If you overfill/fill it then it will just spurt it out of the thin tube on the cylindrical tank which then just vents excess coolant to the road. So in theory coolant finds its own level.

- Option 1 - same as above but put an non-pressurised tank on end of the cylindrical thin tube so that instead of spilling out onto the road any excess coolant is caught in the expansion tank. this will not suck it back into the system as it's non-pressurised. So why do this? - well my problem with the basic system is you cant see how much coolant is in the aluminium cylindrical tank so if you have a clear expansion tank you can see if this level remains fairly constant and if so in theory the level in the main system should be ok (though i would still check it reasonably often). Also it's kinder to the environment than spewing coolant over the road and you have some fluid with which to top the main system up with.

- Option 2 - pressurised recovery system to mimic modern car systems. this will entail fitting a pressurised recovery/expansion tank to the end of the thin tube on the cylindrical tank. On this tank the thin tube should feed the bottom of the pressurised recover/expansion tank and there should be a vent to atmosphere outlet (probably via tube) at top of expansion tank. You now fit a blanking cap to Gerry's cylindrical tank (ie. no spring and not pressure rated) but fit a pressurised cap on the pressurised expansion tank , so the expansion and pressure regulation is now in the expansion tank. You can now fill the original cylindrical tank to the top and when car is warm the coolant will expand and fill the expansion tank....then the clever bit when the coolant cools because of the vacuum effect it will suck the coolant from the expansion tank back into the main cylindrical tank... hence it's now a closed loop recovery system. The benefit of this is some (not much) extra coolant capacity and in theory self management of coolant. However, if you want to go down this route things to consider are:-
- the outlet Ali pipe joint on the top of Gerry's cylindrical tank is a push fit and is probably (mine wasn't) not airtight so will not hold pressure (no surprise as it wasn't designed to)...so you might have to have it welded up.
- you introduce more pressurised hose and joints to leak/fail.
- the choice of expansion tanks is interesting ... i went for plastic Stag with copper top but another member said he had 2 of these fail at the copper/plastic joint.
- people recommend MGB solid copper expansion tanks as being more robust...this is true but you cant see the coolant level so defeats one of the benefits for me.
- i think some Rover/Metro items also fit?

So i tried Option 2 but have reverted to option 1 as it's simpler and lets me know how much coolant has exited the system .

Phew.... Please correct me if I am wrong and i am still interested on what psi cap you fit 10, 13 or 15?

Rgds stuart

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clive
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Re: Coolant catch tank

Post by clive » Sat Aug 10, 2019 3:37 pm

Hi Stuart,

Whilst I agree with what you say in option 1, once the coolant has reached the correct level, you will no longer have coolant spewing over the road.

My rad cap is 13 lbs and has G910 Y6 stamped on it. One other consideration when selecting a rad cap is the depth of the sealing ring as they vary. The first one I tried did not reach far enough into the neck of the expansion tank to seal it so it didn't pressurise.
Cheers, Clive.

(If I'm not here I'm in my workshop or on the golf course!)

stu60
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Re: Coolant catch tank

Post by stu60 » Sat Aug 10, 2019 5:08 pm

Hi Clive
thanks, I agree that once it's reached the correct level it shouldn't spurt any more coolant out but my main issue is i would like to see the level of the coolant and ensure it isn't ejecting any more so all i have to worry about is minimal evaporation.

On the rad cap, that's interesting as I think the cap you've quoted is a short reach one. My car originally arrived with a long reach one which i don't think allowed any pressure release as it was too long! I assume you have this cap fitted to Gerry's cylindrical aluminium header tank?

The joys of individual builds!
Rgds Stuart

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clive
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Re: Coolant catch tank

Post by clive » Sat Aug 10, 2019 5:35 pm

Correct, Gerry's tank. My cap seal touches the bottom of the neck, just!
Cheers, Clive.

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stu60
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Re: Coolant catch tank

Post by stu60 » Sat Aug 10, 2019 7:25 pm

Hi Clive
thanks I have the same set up but just with basic expansion tank.
Stuart

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Re: Coolant catch tank

Post by CobStang » Mon Aug 12, 2019 7:41 am

Option 3
Weld the outlet pipe to the neck on the cylindrical tank to ensure seal. Fit a double seal cap. Run a pipe from outlet pipe into un pressurised vessel with pipe going into top and down to bottom of vessel. Fill cylindrical tank to brim with nose of car in the air and engine running at 1500 rpm, quickly replace cap without dropping revs.
Put 1" of water into over flow vessel to cover pipe.
Car should now expand excess coolant into overflow vessel and suck back when cool keeping cylindrical tank full.

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Re: Coolant catch tank

Post by peterc » Mon Aug 12, 2019 8:08 am

Having now discovered that the rad cap has a vacuum facility then the cap should allow the water in the overflow tank to be sucked back. This allows the use of a non pressurised overflow tank and over comes the less than perfect connection on Gerry’s header tank. Leave the pressure cap on the header tank and the over flow tank can be effectively open topped.
The whole reason I had to embark on having an overflow tank was I needed my water level to be higher than the 1.25” down from the top of the header tank. Eg. I had air in the heater. I guess I had chosen the wrong style of heater compared to what Gerry had intended. Clive, I can only assume that you fitted the correct style heater such you have the 1.25” space in the header tank to allow for when the engine is hot.
Alan managed to over come this problem of water level by raising the header tank. Not having any welding facilities ready to hand I decided not to attempt modifying Gerry’s bracket.
So Jerry fit the non pressurised over flow tank with either 13 or 15 psi cap fitted to Gerry’s header tank. You can witness the over flow tank contents ( suggest running it with 1.5” in it when cold) and when the engine cools down the water otherwise lost to the road will be sucked back in.
Peter C

stu60
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Re: Coolant catch tank

Post by stu60 » Tue Aug 13, 2019 9:35 pm

The other modification that really helps (at least on a Rover V8) is to have a modified thermostat housing. The original Rover one angles up too much and causes the hose to kinks up over the distributor so you get a high point in the hose which is higher/equal to header tank. I dont think this matters in an SD1 or a Land rover as the radiator is even higher but not in the Hawk.

you might need to get a fabricator to modify a thermostat (we modded a TVR unit) and now the inlet pipe from thermostat to cylindrical header tank is defintely lower thank tank so bleeding air is not a problem nor does it necessitate lifting up the front of the car. I can take some pics if anyone is interested?
Stuart

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Re: Coolant catch tank

Post by CobStang » Wed Aug 14, 2019 7:27 pm

Yup, did this years ago on my B.R.A cut the front off, rotated it, welded it up again, much better, nearly flat now.

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Re: Coolant catch tank

Post by peterc » Wed Aug 14, 2019 8:55 pm

Stuart, agree on that one. I now remember that I changed the thermostat housing to keep the top hose lower. Can’t remember who I purchased it from - possibly Real Steel?
Peter C

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