Crossflow Cooling System -Overflow Tank or Expansion Tank

[KS7]

Sorry for the novice question, is the cooling system in a Crossflow a sealed system or a bidirectional system? In other words, is the "tank" which is connected to the filler neck an overflow tank or an expansions tank (bi-directional)? If it is a sealed system, and as the "neck" is higher than any point in the cooling system, it would make sense that the correct "level" of coolant would be at or below the filler neck, allowing for expansion. I would then have to assume that the water pump pushes the water up to the neck to come in contact with the stat to transfer the heat to make the thermostat open.

 

If it is supposed to have a bidirectional cap, I aint got one of those! I just have a standard Motorcraft 100 cap rated at 15psi.

 

Fortunately, I am not having any over heating problems, just simple engineering stupidity!

 

John

[bigdog]

That cap has two seals. A lower one that seals against the inner (smaller) hole above the thermostat and an upper seal that sits on the top of the thermostat housing (just like on a mason jar) The central brass disc on the lower seal is the vacuum release (grab it with your finger nails and it will pull away) and allows coolant to be sucked back into the system. Basically, If your radiator cap has a lower seal only your outboard tank is just an over flow catch tank. Mine has the same cap and it has both seals and the brass disc as well. And here comes a big BUT. My system has never sucked the coolant back into the system from the tank. I suspect that as the nipple near the cap is very corroded. It is probably letting air and not coolant into the system.

[coffee break]

I recently replaced my rad cap. I would guess it was original to the build in 1997. I was getting overflow but no return flow. I installed a new cap and system is well behaved. There is enough room in the tank for expansion and the level in the filler neck looks consistent. The original cap was a 11 lb., I was able to find a 13 lb. and the higher pressure has not been a problem since I have installed a new set of hoses.

[KS7]

Thanks guys! It turned out to be as stupid a solution as the question! The hose was deteriorated near the top of the overflow tank, so in essence, it was unable to allow the return vacuum to reach the bottom of the tank! It looked fine at first glance...thanks again for your support!

[pethier]

Mine is not sucking back the coolant because is the wrong cap. 

 

The problem that causes no automatic refilling of the system is that it has no upper seal.

 

In addition, I think the lower seal is too short.  I don't feel the spring-back when I install the cap.  The vertical distance on both housing and cap is 20mm.  It should be more on the cap than the housing.  Therefore, installing an upper seal on this cap would solve the lack of suck-back, but not solve the fact that the cap will not pressurize the system.

 

Anybody know how to identify and purchase the correct cap for a 1700 Super Sprint?

 

 

[IamScotticus]

my notes on the Ford cap

Rad cap Motorcraft 1613292

Mk1 fiesta

FC52

ERS34

FRC65

Autozone Duralast 7013 / Motorad

 

The cap Burton sells is thier part number FC52.

 

06390 on the cap

This is the cap that came from Caterham 

 

Edited November 23, 2023 by IamScotticus

[pethier]

Thanks!

 

[Wayne Stambaugh]

Noticed this thread and I have been thinking about my 86 S3 BDR. I don’t even know if it had an overflow or expansion tank on it when it was new. Currently there is a bottle up the radiator that is the same as the bottle for washer fluid. I have a feeling that it was just added on and didn’t come with it. As small as the radiator is I would have expected an expansion tank that allowed the antifreeze back into the radiator as it cooled. With a radiator this size I think you want all the coolant you can get all the time.

 

Does anyone know if it came standard with an expansion tank?

[MV8]

A great variety of expansion and overflow recovery tanks have been fitted to various models with different engines over the years. However, I've seen three BDA Cats with the same overflow tank in the same location, plus it is ideally sized and located for the space, so I think the odds are very good that it is oem. Rubber hose through a hole drilled in the top of the tank, forward of the cap and the hose will reach the bottom. Vented tank. May be a small hole in the cap.

Edited November 25, 2023 by MV8

[inchoate]

On 11/25/2023 at 5:12 AM, MV8 said:

A great variety of expansion and overflow recovery tanks have been fitted to various models with different engines over the years. However, I've seen three BDA Cats with the same overflow tank in the same location, plus it is ideally sized and located for the space, so I think the odds are very good that it is oem. Rubber hose through a hole drilled in the top of the tank, forward of the cap and the hose will reach the bottom. Vented tank. May be a small hole in the cap.

 

I can confirm that I've also seen the same setup on every BD powered car I've laid eyes on.  My car uses the same bottle but it's attached to the drivers side footwell instead of being up by the rad.

[IamScotticus]

Cat has been using this bottle for decades

https://caterhamparts.co.uk/oil-system/268-oil-catch-tank-kit-1-litre.html?search_query=catch+tank&results=118

 

My recovery plan going forward will be to use an expansion tank and a recovery tank.

https://howeracing.com/products/surge-tank-horzontal-mount?_pos=1&_sid=7280fa34a&_ss=r

Edited November 28, 2023 by IamScotticus

[Wayne Stambaugh]

19 hours ago, IamScotticus said:

Cat has been using this bottle for decades

https://caterhamparts.co.uk/oil-system/268-oil-catch-tank-kit-1-litre.html?search_query=catch+tank&results=118

 

My recovery plan going forward will be to use an expansion tank and a recovery tank.

https://howeracing.com/products/surge-tank-horzontal-mount?_pos=1&_sid=7280fa34a&_ss=r

Yep, I think that is the tank I have.

[IamScotticus]

I have been seriously considering converting to a closed loop coolant system for the Crossflow.

Someone, [edit]Roger King , said the closed system essentially eliminated head gasket leak issues on his cars.  

This thread proves a point, the traditional "recovery tank" pressure cap is prone to fail and leaving the system sucking air upon cooldown.

In theory, a closed system will not allow this to happen because it eliminates the bypass function pressure cap with an air space in a pressure vessel for thermal expansion and pressurization.  If the vessel is kept only half full, there shouldn't be any fluid loss.

 

I have looked at many tanks on the market and settled on two.  Actually three but one is in UK and other options are easier to obtain.

 

1. Howe racing 3424

https://howeracing.com/collections/radiators/products/surge-tank-horzontal-mount

 

2. Carbuilder HTHB/HTHR

https://www.carbuilder.com/uk/horizontal-header-tank-bottom-brackets

https://www.carbuilder.com/uk/horizontal-header-tank-rear-brackets

 

3.  Moroso 36350/36351/36355/36356

https://www.moroso.com/universal-coolant-expansion-tank63651/

 

In theory, the front filler neck cap will be replaced (or not) with a basic sealing cap allowing the air bleed outlet to flow to the top of the coolant reservoir.  Or, an air bleed at the top of the radiator.  The water pump will draw from the bottom of the reservoir to create the cycle for a self bleeding system.

 

Sounds good to me.

 

Heres the perfect thread about XFlow sealed conversions that has all you need.

https://www.caterhamlotus7.club/forums/topic/262147-sealed-cooling-upgrade-instructions-ford-kent-x-flow/

Edited December 18, 2023 by IamScotticus

[MV8]

When all things are sized, filled, and operating as they should be, an expansion tank can eliminate the need for recovery but that isn't realistic. Pressures typically increase above normal operating pressure right after shut down when flow stops. Assuming the expansion tank is big enough for the system to be half full, the air is compressed with normal use when running. The safety relief valve should be the same or close to the original PSI to help prevent radiator, heater core, or heater valve damage. The safety valves outlet barb needs to be open to loss or a recovery/overflow tank, not back into the closed system.

The only real options to the radiator cap are to be made to fully recover (outer rubber washer) or not and sometimes if there will be a vacuum relief valve (spring loaded center washer shown in the pic of a cat cap). Just having a recovery tank and rubber washer in the cap is not an unreliable system.

 

[speedwagon]

MV8; I totally agree. Where the factory uses a system just like you describe it can be a year or longer before adding fluid is needed. The radiator is always full and the system is never exposed to high pressure until the much feared "blown head gasket" which is a good indicator of being time to dismantle. The old system of a solid cap and a recovery system works well but only up to a much lower coolant temperature.  Besides having only one pressurized system is much safer.  john

[7Westfield]

I have a tank similar to this on mine,except that the lower port is on the front so it can sit lower on the scuttle. Lower port is plumbed to the heater port on the water pump. Upper port goes to the thermostat housing with a -4 braided line. With a couple of holes in the stat it fills easily and works great

 

FWIW    head gaskets on xflows are better than you think.  3-4 years ago, we blew a FF engine because the water pump stopped (lower pulley broke)

water not circulating, so gauge didn't go up

got it hot enough to seize a valve in the guide, and of course it was open, so you know what happened to the piston.....

head gasket was fine

 

https://www.ebay.com/itm/382539232737?hash=item59111d75e1:g:gYMAAOSwNE9kRLG2&amdata=enc%3AAQAIAAAA0AsBkwM0otc9BdLPcwCtpoxz7hYCOV3H7cBI0jB4nhFhr9KA5C6E2Je45rRktOXefYeugBo7LxE75r47B5jTbHi7gCWAhkJ9ySUW4cH3LB0evB1vzbm7ewqxPmOjCtntlcHgMzSsgK3PtDQVyHjr40u91gEOSustAfh6097g73y5UTEdxuWIso9dt%2FiMtYPf3fGuvPyEfFh78SAXK4hraYp4y4DFUKToybBvtkIgRifoTEIzuXKXaSH%2Bh3oRqxKMtkT336oGF7xsuFMi6QMoUls%3D|tkp%3ABk9SR8DOx8KKYw

Edited December 10, 2023 by 7Westfield

[IamScotticus]

Is a half full >1ltr  expansion tank large enough to not need a recovery tank?

Edited December 10, 2023 by IamScotticus

[7Westfield]

yep

 

or, this one's a bit larger

 

https://www.summitracing.com/parts/sum-300116

 

just went out and measured mine.....it's a Cannon brand, but same as the Summit unit

Edited December 10, 2023 by 7Westfield

[IamScotticus]

In my search for the perfect expansion tank, or bottle, or header tank, I have found this one that has been used by Lotus on Rover K engined G1 Elise and Exige and by Caterham on various 7 around 2015.

Lotus part number A111K6004F.  Uses cap A111K6001F and bracket C111K0003F.  Rover 600.  Available from Lotus and Rimmer Bros.

 

If the Loti becomes unobtanium, there is a close second, the Rover 25 tank, PCF010086 (thanks, Roadsport06)

 

Edited January 12 by IamScotticus

[IamScotticus]

Hello,

Its time for some updates on the subject.  None of this is new, just new to me.

 

I want to make it clear, the Cross flow open coolant system works, and if the radiator cap is working and the recovery tank coolant level is kept adequately for cool down return, and all the functions of the radiator cap are working, the open loop system works very well.

 

My reading about the merrits of the closed loop system has convinced me that the purpose of it is to eliminate many of the points of failure of the radiator cap.

 

My research has also shown that plastic expansion tanks and the pressure caps can have a high failure rate, depending on quality. These can have a greater failure rate than an open system. A plastic expansion tank will leak from its seams and caps will fail allowing boil-off. You should usually see evidence of this from pooling or seeing coolant level loss in the tank. When possible, buy OEM quality for these.

 

Another option is use a metal surge/expansion tank and pressure cap. These have the advantage of absolute reliability and caps are available in a variety of pressure rates.

 

The open system can be a silent killer failing to drawback overflow or a cracked cap gasket letting loose at the worst possible time. (ask me how I know)

Pick your poisons.  

 

The only engines Caterham have used open systems on have been the Kents.

 

I am not pursuing a metal tank now but if I did, 

 

https://www.carbuilder.com/uk/horizontal-header-tank-bottom-brackets

 

https://www.carbuilder.com/uk/horizontal-header-tank-rear-brackets

 

And there are other good tanks.

 

 

Moving on...

 

I have sourced some new parts for the closed conversion:

 

Amazon, of course

 

And: 

 

Fiesta Mk2/3/4    PN:6814635

 

 

 

Samco Sport Hose kit:

 

 

The hose kit comes with 3'7" x 5/8" heater hose, perfect for the smaller expansion tanks. That length is the length from the rad mount to the footwell shelf edge. Maybe a little short for a scuttle mounted bottle to a lower hose Tee, but adequate for anywhere else.  No top bleeder hose.

https://samcosport.com/product-category/car-kits/caterham-7/

 

 

 

Lets discuss this tank, the Rover series 200 & 400, PN: EAP8713, and its cap, Rover PCD100160. 

 

It was used by Caterham on the K Series, Sigma and early Duratecs and mounted on the front top chassis cross tube. It's a fine tank but I found the Crossflow is mounted too far forward to use it on the provided brackets.  The hoses would be touching and there may be a height problem too.  If mounted high enough to clear the Fiesta TH, would it clear and fit under the nose?

 

Plenty of room for the K

 

Others have been able to use the 200/400 tank on the scuttle.

Notice the cap appears to not be the standard Rover cap.

Notice the fiesta thermo housings used.

Where do those "7" branded cases come from?

 

I like this Rover 200/400 tank but it's getting hard to source.

The pressures for the Rover caps are ideal, in the 100 bar, 16 psi range, and the mid point fill volume is 20oz.  I would prefer a taller and narrower tank to keep slosh away from the cap.  5/8" outlet.

Failing other options,I will use it.

 

The Rover 600:

Used by Caterham and Lotus. Uses aforementioned Rover cap.   

Also used on the Lotus Elise.  There's your cool Lotus connection.

I really like this tank, but those stubby legs are worrisome to me.

Cat parts still has the bracket

 

 

The 600s close cousin, the Rover 25:

Longer legs are probably an improvement.

 

The ubiquitous Land Rover Freelander:

Used by CC on everything after the Rover 600 tank.

The mount for this crews into the boss in the center of the top cruciform.  

You always wondered what the was for, didn't you?

 

There are other options..

 

The Westfield standard appears to be Opel Corsa:

 

 

 

The Dacia Duster / Renault Kangoo

 

I heard from one other L7C member that uses this tank on his/hers BDR.

21psi cap.

 

I found some other miscellaneous Crossflow applications:

Birkin, I believe.  Anyone know this tank?

 

 

As for how to plumb, the tank flow is top to bottom. The top inlet nipple is usually plumbed to a high point such as a radiator air bleed or thermostat housing. 

 

The bottom outlet is usually plumbed to the cold side between the radiator and pump inlet. It needs to be on a suction part of the circuit where coolant will be drawn out of the tank and thus, pulling air & coolant from the bleed hose location which no longer needs to be the high point, but it helps.

 

On a Crossflow, if the pump heater inlet pipe is available, use it. If a heater is plumbed, tap into the return hose going to the pump. If running a straight line from the carb manifold to the pump, tee into that. But not if using a coolant controlled carb choke. If neither heater circuit is available, tee into the lower radiator hose.

 

Because an expansion tank is never completely filled, the air gap retains the purged air (closed) and excess pressure is vented out the cap, which should be the highest point of the system.

 

The coolant is allowed to expand and retract and contain sudden acceleration surges within in this vessel.

 

In the UK, Crossflow closed system kits have been sold by Arrowstar and James Whiting.

Edited January 22 by IamScotticus