BX Radiator Swap

Ian Fearn · Post by **Ian Fearn** » 29 Dec 2004, 19:49

Merry Christmas chaps, can anybody give me some advice about flushing my BX GTI cooling system?
I've just pulled out the radiator and have tried to find all the bleed screws. Theres one behind the cam cover (allen key screw), one on the thermostat (looks like a tyre valve cap) and one about 2 inches away from the thermostat (plastic screw).
Are there anymore?
I ask as when i put the hose pipe down the top radiator hose to flush the system through it just spurts out the hose again and doesnt run round the system and come out the bottom hose, should it?
What is the correct procedure for doing this?
Any help greatly appreciated.
From somebody with a dead BX (AGAIN!)

oilyspanner · Post by **oilyspanner** » 29 Dec 2004, 20:09

Remove the radiator stand it on end (side) with the bottom hose stub uppermost and stick yer pipe in there, I usually shake em too and watch that clag run out, I position mine over the yard drain so as not to dye the concrete brown!
Stewart

Ian Fearn · Post by **Ian Fearn** » 29 Dec 2004, 22:04

The old rad is going in the bin, i've got a new one.
I'm trying to clean out all the pipes and also understand why when i put a hose in one end, water doesnt flow through the system, just comes straight back out again?
Does the water pump block the flow maybe?

AndersDK · Post by **AndersDK** » 29 Dec 2004, 22:13

Not the pump - but the thermostat blocks the waterways [:)]

Ian Fearn · Post by **Ian Fearn** » 29 Dec 2004, 22:23

So if the thermostat blocks the waterways, is there any way of opening it up to thoroughly clean out the old pipes or is it a case of undoing each pipe and cleaning it that way?

prm · Post by **prm** » 29 Dec 2004, 22:40

Ian
While your there !! With new rad --- Very wise decision.
Don't forget,--- new rad thermo switch -- the lower temp TZD one, thermostat and new bottom hose.
Found these hoses to be very soft, 2-4 inches out from pump side fixing point. Collapse inwards on pump suction, especially after a cam belt replacement due to the movement of engine during replacement, weakening hose construction.
R

AndersDK · Post by **AndersDK** » 29 Dec 2004, 22:44

The thermostat opens at some 85degC - no mechanical way to open it. You will have to remove it from the thermostat housing.
As the thermostat is only some £6 replace it - together with the fan thermoswitch as Peter suggests.

Ian Fearn · Post by **Ian Fearn** » 29 Dec 2004, 22:50

The plan was the replace the thermostat and fan switch anyway, but as its just had a new cambelt i'll pay close attention to the lower hose as well.
After going out in my mates BX GTI 4x4 i realised how hot my car runs compared to his, hence the reason for all this work! In traffic the temp really goes towards the worrying end of the scale and i've only ran it since october so god only knows what it'll be like in summer.
I'm not convinced my fan has ever come on to be honest, also how would i know if the thermostat is working?

prm · Post by **prm** » 29 Dec 2004, 22:53

Ian
Is that the Hurricane you beat me to on eBay ??
Bristol way.
Agree -- Didn't want to frighten Oscar off !! LOL
I think I'm approaching £700-800 with 16v rebuild and still spending, and enjoying it.
R

Ian Fearn · Post by **Ian Fearn** » 29 Dec 2004, 22:58

PRM,
After the ICCCR in Switzerland i HAD to have a BX, after my Uncle bought a 19GTI 'G910 NNN' brand new on 1st August 1990 its been imprinted in me since!
I got mine off BX16V.com from a chap in Rotherham, only paid 300quid for it and yes it was the first one i saw but i had to drive from Derby to get it as BX's doesnt come along that often anymore.
I'm a bit of a perfectionist which to be honest is the reason i've spent so much on it. The figure is getting close towards the 2 grand mark now and is still going up!
What are you doing to the 16v?

prm · Post by **prm** » 29 Dec 2004, 23:25

Ian
Sorry-- I have seen your postings on the 16v forum.
Trying to return 16v to original spec and recently been a struggle to keep ahead of mechanical/ECU/EFI problems.
Almost met its maker.
Finally now on the winning side.
Good news with your rad etc. replacements. Had almost identical high temp cooling problems. Replaced rad, switch, thermostat (82c) and hoses. Now cured.
To give you a guide that thermostat is working. From a cold start-up. Temp gauge will rise to around 90, then drop back to 85ish when stat fully opens, then rise again to 90ish when the cooling fans, on slow speed, should cut in and control water temp, stationary.
Are there twin cooling fans on Hurricane ??
R

Ian Fearn · Post by **Ian Fearn** » 30 Dec 2004, 15:01

I've got the single fan.
I still dont understand the correct procedure for bleeding the system though[?]
Do i open the rad bleed screw and the thermostat bleed screw, fill up the system until coolant comes through the thermostat screw then shut it off, then do the same until water comes out the radiator?
What about the bleed screw behind the cam cover and the plastic one thats right next so the thermostat?

prm · Post by **prm** » 30 Dec 2004, 20:29

BX cooling systems can be a pain sometimes to remove all the air from the system and may have to be repeated several times.
From a cold engine. Turn heater valve to max. Remove bleed screws from rad, thermostat (there maybe two) and rear pipe. Check that any central holes in screws are clear. Fill system slowly until bubble free coolant flows from rad then close. same with rear pipe, then thermostat. Fill system to nearly max. With rad cap removed, start and run until normal temp, 85-90ish, or fans cut-in on slow speed.
Open bleed screws, one at a time to vent any remaining air.
They may have to be removed completely. Keeping coolant about 25-35mm from the top and revving engine between each operation. Allow engine to cool. Refit rad cap, run engine again to pressurise system to normal temp and yes -- bleed again.
Hope this may help.
When your in the breakers next, keep your eyes open for a twin fan set-up. Well worth it.
R

Ian Fearn · Post by **Ian Fearn** » 30 Dec 2004, 22:29

Today i removed the thermostat to REALLY clear the system out (it was full of brown water!!).
When i refit the new rad tommorrow (new thermostat, rad cap and fan switch arriving tommorrow) i thought that coolant wouldn't pass through the thermostat until it was above 85-90ish degrees? Hence i wont get any water coming through the rearmost bleed screw with a cold engine? OR WILL IT???

prm · Post by **prm** » 30 Dec 2004, 23:08

As you fill the system, coolant will come out from both thermostat housing bleed screws. As the thermostat is closed, trapping any flow, you need to bleed both sides of this housing. Bleed rad and rear pipe, then thermostat housing --outlet to bottom rad hose first, then the one to the rear of the thermostat. Your just working your way through a general head/height of coolant with this order, displacing any air.
Keep an eye on new rad thermo switch connection. Should be the same configuration ?? One horizontal and two vertical. The vertical one to the right should be fan slow speed. Just interchange both vertical connections to verify both high and slow speeds once the system is up to around 88-92C. Depending on temp ratings on new thermo switch. High speed should cut-in around 92-98C.
Always used 50% antifreeze, mixed with boiled and then cooled water.
R