VX Carbs Inlet Manifold Coolant/Air Bleed

[Paul McKenzie]

I'm having problems with blow-out of coolant from the expansion tank with a newly built top end on my HPC. It doesn't happen when the engine is running, but as soon as I turn the ignition off the expansion tank pukes out about 0.2L and remains full even when cold.

 

My engine builder reckons the spigot on the inlet manifold which connects to the top of the expansion tank contains a ball-valve which was jammed when he rebuilt the top end. He manged to free this, but it seems we could do with a replacement. However, none are available ☹️.

 

What we are considering is pressing out the ball and then putting a restrictor in the hose, which is what I read the VX challenge cars used to do, although I don't know whether they had a ball valve there in the first place

 

Anybody got any experience of this mod please? Alternatively has anyone who's ditched the standard inlet manifold have one kicking around or even just the spigot valve?

 

Cheers

 

Paul

 

 

 

Edited by - Paul McKenzie on 26 Mar 2012 19:06:37

 

Edited by - Paul McKenzie on 26 Mar 2012 19:07:28

[k.russell]

mine has a restrictor in the hose with a 2mm hole through it, pushed in at the expansion tank end. slight problems similar to yours towards the back end of last summer, i think due to the hole blocking, still to test this though, ran into winter. before proving fully that this was the case. lots on archive i recon if you search for restrictor. worth a try for pennies it costs.

[Paul McKenzie]

Thanks, but do you have the ball valve as well? There's little or nothing, just a couple of mentions, in the archives about the ball valve, as I think most of us, myself included, didn't realise it was there . In fact, I spoke withh CC today and they said "yes" then to Red LIne and they said "no"

 

Edited by - Paul McKenzie on 26 Mar 2012 20:58:52

[Bob Simon]

FWIW...

 

I tried the restrictor method for a while with moderate success. The tank would still belch under extreme heat conditions.

 

I eventually bored out the AN fitting threaded into my manifold and press fit an original Opel/Vauxhall check valve. No more problems under any conditions.

 

I can't remember where I got the valve, but it was from one of the usual VX speed parts houses.

 

 

[k.russell]

paul, sorry no ball valve in my direct throttle bodies, pretty sure there wasnt in the manifold either.

[Paul McKenzie]

Quoting Bob Simon: 

FWIW...

 

I tried the restrictor method for a while with moderate success. The tank would still belch under extreme heat conditions.

 

I eventually bored out the AN fitting threaded into my manifold and press fit an original Opel/Vauxhall check valve. No more problems under any conditions.

 

I can't remember where I got the valve, but it was from one of the usual VX speed parts houses.

 

 

 

Bob, Can you give me any more info to identify the check valve you installed - I've done a few Google searches but not come up with anything

 

[Bob Simon]

Paul, Looking through my notes, I discovered the valve was originally pressed into a Caterham 45DCOE manifold on a car that was being converted to FI. It may not have been off of a Opel/Vauhall car. As it turns out, it was given to me in a swap of spares at one time or another. I think just about any tiny one way valve would work.

 

This whole bleed line issue is very confusing. I recall that if there is no restriction or check the line, there is a constant flow of coolant from the head into the expansion tank through the bleed line. Why is that? Evidently, the bleed line completes a loop directly from the inlet of the pump through the 16mm manifold bypass pipe and back to the tank.

 

I notice That SBD doesn't mention using a restriction or check, however they also run the bleed line through a T piece to the top of the rad.

 

I've a mate that specializes in cooling systems. I'll ask him what he thinks about all this.

[Paul McKenzie]

Thanks for that Bob. I've now discovered that what it's called is a 'jiggle valve', and as I said Redline couldn't recall the valve being there in the VX manifold, although CC did. I must admit I had no idea the jiggle valve was in that spigot and I thought I had fairly good knowledge of the Caterham Vauxhall setup.

 

What I've also learned is that it is also in the K series manifold - I wonder how many K owners know that as it gets little or no mention in the archives, and I would guess it has probably played it's part in helping along the odd HGF issue .

 

The way I understand it is the function of the jiggle valve in the manifold is to allow a small bleed of coolant and any trapped air into the airspace above the coolant in the expansion tank while not over pressurising the expansion tank. When the valve sticks closed due to corrosion product or other any contaminant in the coolant, then the coolant takes the alternative route from the manifold through larger diameter offtake and hose directly in the bottom of the expansion tank. This fills and pressurises the tank and thar she blows . Any air locks in the head make the situation worse due to localised hotspots which would lead to boiling and steam generation.

[Mavic82]

Mine has the ball valve, it can tend to get stuck every year or so. Pull the hose off and with some wire it can be cleaned/ freed off again.

 

I also run this hose into a T that goes to the header tank and the other to the top of the rad. Makes bleeding easy

[Bob Simon]

Bingo!

 

My mate says the same. It's a "jiggler valve", not a check valve. Air goes through but fluid doesn't. If you google "jiggler valve" under "images", the fourth picture shown is the jiggler in an cheese block intake manifold. Unfortunately, the K series valve is overmolded into the manifold and not replaceable.

 

Slightly OT, but he mentioned jigglers are most often found in the thermostat. They allow air to bleed through after changing out the stat. Very much like the common practice of drilling a tiny hole through the stat in a VX. BTW...wedging an aspirin tablet in the stat during replacement will also insure a good air bleed when filling up the coolant system. I thought that was pretty damn clever.

 

I also found the coolant system schematic for an LS Chevrolet (Corvette) while perusing the web. Chevrolet uses a bleed from the top of the rad as well as the one from the high point in the engine. there is no "jiggler valve", just a simple restriction at the expansion tank. Go figure.

 

I believe the ultimate setup would be running both head and top of rad bleed lines to the expansion tank as Guy has done. Jiggler vs restrictor? I dunno... probably doesn't really matter.

 

 

 

 

 

[Bob Simon]

This might work.

Honda motorcycle part number 19410-MCT-000, Joint, Jiggle Valve.

18 squid.

[Paul McKenzie]

Yes, that might do the job. My engine builder is going to make a couple of jiggle valves from the CC pattern but using stainless steel. I'll see how that goes.