Vauxhall C20XE cooling question

[keybaud]

The larger cooling outlet from my C20XE cylinder-head, inlet manifold is blocked off and, as the car has no heater, it only has a single tower cooling submarine. The smaller outlet on the head is conencted to the expansion tank. I have been informed me that although it is common to block the larger outlet, it can cause problems, and I've also noticed that the single outlet submarine isn't listed as a Caterham part for the Vauxhall 16v S3.

 

Does anyone know if this is a Caterham specific design for the Vauxhall Challenge car or, as the car is being worked on, should I replace the cooling submarine with a 2 tower variant and open up and connect the water outlet on the inlet manifold?

 

The pipe that is missing is the one indicated by the large arrow head pointing down from the inlet manifold on both pictures at the SBD cooling system link below:

 

http://www.sbdev.co.uk/Info_sheets/Cooling_systems/Cooling_system.htm

 

The one issue I can think of is that without this pipe, the cooling system is static until the thermostat opens, which could lead to hot spots within the engine, although there will be some flow via the expansion tank from the smaller pipe XY to XZ.

 

 

Edited by - keybaud on 9 May 2012 23:13:19

[Lee Fowler]

I will take some pics of mine later today and mail them over.

 

Lee

[Garibaldi]

The coolant outlet from the inlet manifold should ideally be open allowing coolant to flow so you would need a two tower sub pipe...

When I removed my heater I ran a pipe from that outlet on the head round to a third tower on the sub pipe to maintain a good flow of coolant and minimise hotspots.

I made a custom alloy sub pipe to do this.

The car is on throttle boddies (so cooling layout for carbs) but has the cooling layout of the original Vx injection with the above mod.

Cheers

Gary

 

[keybaud]

I emailed Darren at Caterham about this, and he said that on my car the outlet is blocked, as connecting it to the water pump can cause aeration problems. I assume that this is a problem as there is no heater, so there is no connection at the back of the head to the heater matrix, thus removing the path for that any aerated water would otherwise take. I assume that the small outlet from the inlet manifold to the expansion tank, which has a medium-size connection to the submarine tower, provides sufficient flow to prevent hot spots within the engine.

 

Any more ideas/discussion/comments welcome.

[Lee Fowler]

YHM.

 

Lee

[Bob Simon]

The pipe from the manifold to the sub tube is the thermostat bypass. It keeps the pump from pushing against a solid column of coolant that has no place to go when the stat is closed.

 

connecting it to the water pump can cause aeration problems.

 

I could only see this as a problem if one is using a single stage stat. The standard two stage stat closes off the bypass loop when the primary stage is open, sending flow through the rad.

 

I'm not sure if the tap on the back of the head needs to be nippled up to the sub tube. I see a lot of XEs with this connection blanked off. Mine is.

[keybaud]

Quoting Bob Simon: 

The pipe from the manifold to the sub tube is the thermostat bypass. It keeps the pump from pushing against a solid column of coolant that has no place to go when the stat is closed.

 

There isn't a solid body of water, as there is still a smaller pipe that feeds the expansion tank, which then feeds the water pump, so the water is moving. Unfortunately, I can't find any drawings or cutaways of the head to understand what the actual flow pattern is, as I'd like to know how the water flows around the head. From what I can remember (the car isn't here at the moment), the feedback loop from the thermostat housing is a similar diameter to the small pipe on the manifold.

 

Edited by - keybaud on 10 May 2012 19:16:21

[kenny.]

I had a similar dillema when I removed my heater from my previous 7....a VX 218 Evo.

 

I found that on removal simply connecting the pipe from the sub tube to back of head was more awkward than imagined. Unlike the SBD diagram the push in connector on back of head is shorter than that and getting the bend on pipe without putting more joints in it looked naff, and strained in all honesty. So I too decided to blank off, especially when someone told me Swindon supply a bung for the head. I called Swindon and they actually advised not to blank off 😳.......they advised piping it up.

 

So, I eventually persuaded the original push in tube out........bloody hell it was stuck, and tapped hole with a BSP thread.......I forget now but the hole is perfect for a particular BSP thread. I then found a connector which lent itself to getting the correct angle for silicon hose from sub to attatch nicely..........car then ran an even sub 90 degree temp all over head, even after a thrashing according to my laser thermo.

 

PS

Will get number you require today.

[ECR]

I attempted a description of the flow in the head. It's a long time ago now and I'm not sure how clear this will be but here goes:

 

Water Flow in Cylinder head

 

Definitions:

E = outlet from rear of head

 

B = upper hole nearside of cylinder head (thermostat block)

A = lower hole nearside of cylinder head (thermostat block)

 

C = upper hole offside of cylinder head

D = lower hole offside of cylinder head

 

When the engine is cold and the thermostat is closed water can not flow from B to the radiator. Instead it is diverted from B through the upper head gallery to A. This keeps a flow of water around the head cavity (but does not allow it to be cooled through the radiator). This warms up the engine more quickly. When the thermostat opens the flow of water from B to A is closed off and B then flows through the radiator, cooling the supply.

 

Water poured in at E exits at A and D (lower gallery)

Water poured in at B exits at C (upper gallery)

C and D are connected via a tiny bleed channel in the inlet manifold gasket

 

[Bob Simon]

There isn't a solid body of water, as there is still a smaller pipe that feeds the expansion tank, which then feeds the water pump, so the water is moving.

 

Not really. The smaller pipe is only there to allow air trapped in the upper reaches of the head to bleed into the expansion tank. It's usually restricted by a jiggle valve or 1-2mm restrictor to stop or minimize the flow of coolant. The intent is that only bleed air flows though this hose, not coolant.

 

ECR has the flow paths in the head correct. Most modern engines use this type of two stage stat system. Years ago manufacturers simply bypassed through a small hose without a two stage stat.

 

As to the tap in the dizzy end of the head?

I'm not sure whether this really promotes better cooling or not. It would make sense, however, the XE engines in BTCC and vintage F3 cars do not use this connection.

It certainly wouldn't hurt to keep the rear of the head connected to the pump inlet, although some coolant won't ever see heat transfer since it loops straight back to the pump, bypassing the rad.

 

One other thought;

It seems GM wanted flow though the back of the head at all times as the heater matrix valve in a Calibra ( and other models) is a bypass style arrangement. Coolant still flows when the heater valve is set to off. Go figure.

 

edited to say: GM may have been thinking that the passenger compartment would heat better/faster with less coolant flowing through the rad???

 

 

 

 

 

Edited by - Bob Simon on 11 May 2012 12:55:27

[keybaud]

Quoting ECR: 

I attempted a description of the flow in the head. It's a long time ago now and I'm not sure how clear this will be but here goes:

 

Water Flow in Cylinder head

 

Definitions:

E = outlet from rear of head

 

B = upper hole nearside of cylinder head (thermostat block)

A = lower hole nearside of cylinder head (thermostat block)

 

C = upper hole offside of cylinder head

D = lower hole offside of cylinder head

 

When the engine is cold and the thermostat is closed water can not flow from B to the radiator. Instead it is diverted from B through the upper head gallery to A. This keeps a flow of water around the head cavity (but does not allow it to be cooled through the radiator). This warms up the engine more quickly. When the thermostat opens the flow of water from B to A is closed off and B then flows through the radiator, cooling the supply.

 

Water poured in at E exits at A and D (lower gallery)

Water poured in at B exits at C (upper gallery)

C and D are connected via a tiny bleed channel in the inlet manifold gasket

 

Apologies for being slow, but I'm still confused as your description doesn't take into account the path from the water pump. Using your notation, where does the water go when it is poured into the head via the water pump? I can then work out what effect this will have on my head, which has both E and D blanked off.

 

Also, when the thermostat opens, does it close A or is the flow rate through B large enough that the flow back through A is no longer relevant? It may even reverse the flow direction through A by the venturi effect.

[Bob Simon]

KB,

 

For simplicity's sake, I'm leaving the port in the back of the head (port E) out of this description. I'm leaving the air venting bleed out as well (port C).

 

The pump pushes coolant into the jacketed areas surrounding the cylinders in the block. The coolant then is forced up through the head gasket into the areas of the cylinder head surrounding the combustion chambers. It exits through the upper hole in the exhaust side of the head (port B). The thermostat prevents this flow from continuing on to the radiator when closed.

 

The bypass is an isolated path through the head from the lower hole in the exhaust side (port A) to the lower hole in the intake side (port D). _{There is no connection to the water jackets in the head or the block.} This path is simply the manufacturer's method of eliminating an external hose to get the bypass from one side of the engine to the other.

 

The thermostat housing acts like a two way valve. It controls whether the coolant goes through the rad or through the bypass back to the pump inlet.

 

When the stat is closed, the bottom section of the valve allows coolant from the upper hole in the exhaust side (port B) of the head to flow freely to the lower hole on exhaust side (port A). The coolant passes through the head to the lower hole in the intake side (port D) then on to the pump inlet (submarine tube).

 

When the stat is open, the lower hole in the exhaust side (port A) is shut off and all flow goes to the radiator. There is no flow though the bypass port.

 

In it's simplest form, the engine could be run with only a connection from the upper hole in the exhaust side (port B) to the radiator (no stat housing) and a connection from the radiator to the pump. The lower holes in the head (ports A and D) could be open to atmosphere and there would be no leaks. The upper vent hole in the intake side (port C) would have to be blocked as it does penetrate the head's water jacket.

 

Next week: plumbing a PW reactor. 😬

 

[keybaud]

Thank you, everyone. I don't have the car to hand and the spare engine doesn't have a thermostat inside the housing, so it's been a brain stretching execrise for me.

 

I can now see how the thermostat closes B, which wasn't obvious without a thermostat inside it, and I now know what purpose D serves. I can't see any reason why Caterham would recommend keeping D blocked, so I'll get a 2 tower submarine, another piece of hose and open up the port.