MK1 heater matrix with VR6 engine

Was going to connect up the heater pipes from the engine bay to the heater matrix tonight with the new heater valve that is in the engine bay and then realised that the Samco VR6 pipe i have doesn't allow for the valve.  After some reading it sounds as though later Mk2 and Mk3 cars don't have the valve like the MK1 and instead have a bypass valve within the coolant system to control the coolant going through the matrix and therefore the heat.

So, how should i go about connecting up my heater matrix to the heater pipes so that i have a working heater?  I know i can connect the two heater pipes within the bay (as they were done by the previous owner) but i'm a southern softee and will need a heater come Autumn     But i don't want the heater on full all the time!

Does anyone know if my assumptions above are correct about the flow of coolant, and does anyone know if i could fit a Mk3 matrix to my campaign?  The measurements look identical, but the pipe outlets from the matrix come off at the wrong angle compared to the MK1 matrix.  I guess some sort of connectors need to be made up?

Dimensions (234x156x42mm)

My Mk1 matrix



VR6 matrix

you'll have to cut the vr6 pipe somewhere and insert your valve inline.

the mk2/3 doesnt have any kind of valve instead it has a flap inside the airbox that diverts air around it when you set the heaters to cold, so no matter what coolant is always circulating

If i insert the valve will this not stop the circulation of coolant, and this goes against what the Mk2/3 does?

If it is Ok to stop the circulation, the Mk1 valve outlets are smaller than the VR6 Samco pipes width, therefore i guess i'll need reducers or another valve??

you have to use some kind of coolant valve with a mk1 dash, otherwise you wont be able to turn off the heat! on the mk2/3 there is no valve, instead a flap is used inside the airbox to divert cold air around the matrix.

the mk2/3 matrix is totally different to the mk1 so it would be virtually impossible to fit one unless you also convert the airbox setup inside the car to mk2/3

as you say you'll need reducers or some other kind of coolant valve with larger diameter outlets

Thanks John.

I'm going to have to have a think and see if i can find a way to make sure that i can use the valve so that i'm not sweating with the heater on all the time, but that if i close the valve that i'm not stopping the flow of coolant around the system and causing hotspots within the pipes.

Could i use a couple of 3 way junctions (if i can find one) so that flow moves around the heater matrix with the valve open, but continues to flow if the valve is closed, something like below in my work of art!!

There's been a few MK1 VR6's done before. How did other conversions get round this?

Usually the two pipes are joined so the flow of coolant doesn't even reach the heater matrix, I.e. no heater.  Ok in the US but not over here with our weather  

The car when i got it had a socket (not sure what size     ) used as the connector.  I can do it this way if i have to, but i'd rather get it so that i have a heater, even if it's just for the demister!

I'm searching Vortex at the moment to see if i can find any solutions.

ah sorry i see what you meant now yes you'll want some kind of bypass pipe if blockign the matrix pipe stops proper flow, assuming that its even a problem on the vr6?

on 4 cylinder engines yes the matrix pipe when blocked would stop coolant flowing round the cylinder head properly hence why they have a bypass, but you may not need to on the VR6 depending how the coolant pipes are plumbed, I'm no expert on them so cant really offer you any help there.

If it is an issue then plumbing it as per your piccy would be fine

Ah ok mate. Yeah you're gonna need the heater if you're driving about in the UK winter weather

Hope you find a solution mate.

have a look around the scrappy at mk4 eara cars, I'm sure I have seen T pieces which look like they would do the job nicely, 2 matrix size feeds and a smaller feed for something else?

Cheers i'll head over to the VR6 forum and ask them on there.

THIS might be of help mate albeit a short thread.  

And HERE has got a MK1 VR6 conversion help section. There might be something in there dude

Cheers for those links.  The first one i had seen when i discovered about the flow of coolant.  

Onwards and more searching  

A guy on the VR6 forum said that he was concerned about the flow so added a hose before the valve so if the valve is closed for cold air, the coolant can still flow around the system.

I've measured the hoses both original Mk1 and Samco VR6 and i think i need a 19mm > 16mm reducer.  Found these on eBay:




The measurements are 19mm > 16mm > 19mm so i'll get a short piece of 19mm blue silicon hose to run between the 2 hoses going into the heater matrix but before the valve.  

Could be just what you need mate to get it working. Let us know how you get on with it