vr6 disaster

[davevw 0]

hi just changed water pump on my vr6,filled her up with nice new coolant then took it out for a spin.After driving 20 mins steam poured out from radio hole in the dash ,resulting in soaking wet carpets.Have i forgot to do something or am i just unlucky and the heater matrix has failed!

[davidwort 0]

sounds like the dreaded failed matrix, it could be some problem with your cooling system that has caused the weakest point to fail each time though?

[Supercharged 2]

Which water pump did you change??

 

It's the electric one on the VR that takes the pressure off the matrix...

[davevw 0]

no i changed the main water pump ,original one from vw

[Supercharged 2]

Ok, maybe worth checking the electric one is working too when you do the matrix...

[dr_mat 0]

Yeah, probably the old pump wasn't pumping very hard .. the new one get's the system up to full flow and the matrix can't cope any longer.

[davevw 0]

how can you check the electric auxillary pump is ok

[dr_mat 0]

Turn the ignition on, you should hear it whirring very quietly, and you'll see a slightly movement in the water through the expansion tank.

[Dude VR6 0]

I`d check your thermosat as well, I had this problem with a burst matrix and it was down to a jammed closed thermosat. Which resulted in the engine getting to hot and pressurising the cooling system, and finding the weakest point to blow.

[davevw 0]

yes thats whats happening now ,ive bypassed the heater matrix now the cooling system is pressurising

[dr_mat 0]

If it happens immediately after a breakage, chances are you have an air lock.. You'll know if the thermostat doesn't work - the rad will stay cool!

[Dude VR6 0]

yes thats whats happening now ,ive bypassed the heater matrix now the cooling system is pressurising

I did the same mate, the cooling system is a self bleeding system and you shouldn`t have problems purging it, but if it pressuring the system, I would check the stat before you go any further. You may get it to hot and warp the head.

[davevw 0]

it seems in changing the water pump has opened up a can of worms

[Toad 0]

How did you refill the system? They're quite easy to get air locks in.

[davevw 0]

refilled the system from coolant bottle ,then ran engine to allow escape of air out of system.Would an airlock cause the matrix to pop ?

[Dude VR6 0]

How did you refill the system? They're quite easy to get air locks in.

just filled the system, and run it up, kept topping it up till it was to the level

[Toad 0]

That doesn't always work...

 

You should take the top rad hose off and fill through that, slowly, then run it up to temp with the cap off till the bubbles disappear. I've airlocked my VR before whilst being extra careful.

 

And yes, it does increase the pressure on the system.

[Dude VR6 0]

That doesn't always work...

 

You should take the top rad hose off and fill through that, slowly, then run it up to temp with the cap off till the bubbles disappear. I've airlocked my VR before whilst being extra careful.

 

And yes, it does increase the pressure on the system.

I never had a problem bleeding mine, probably because I only changed the stat & housing and didn`t lose to much fluid

[davevw 0]

could a failed thermostat cause a build up of pressure in the system as well?

[Dude VR6 0]

could a failed thermostat cause a build up of pressure in the system as well?

 

As I found out with mine, the stat was jammed shut, so it did pressurise the system as it would boil up creating bubbles, pressurising the system.

[dr_mat 0]

Actually it's less about the pressure and more about the heat. The system is designed to withstand pressure, no problems. In fact it's designed to retain enough pressure that the water in the system can become superheated (i.e. it can go over 100 degrees C without turning into steam). So what happens when you have an airlock is you actually don't have *enough* pressure and the fluid starts vapourising. The pockets of vapour moving around the system are MUCH hotter than the fluid would have been, so not only do they fail to cool the engine in the bit where they're sat, but they also have a tendency to superheat joints, fittings, pipes and so on, finding or creating leaks much sooner than a pressurised fluid at 100 degrees would.

 

So retop up the system as described above - using the top radiator hose - and run the engine again, to be sure you've got rid of all the air locks before you assume anything else is wrong.

[Supercharged 2]

Also make sure you have a genuine new style blue cap fitted to the expansion tank!

[davevw 0]

just had sniffer test done ,headgaskets failed,leaking into cooling system and pressurising it.Did not notice anything as car is only used for short journeys to and from work.Probaly what caused matrix to pop ,its getting fairly expensive, should have kept my mk1