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Direct Link To This Post Topic: Bleeding the cooling system
    Posted: 20 Aug 08 at 22:47
Other topic went missing, there some of it somewhere someone helpfully pasted back in, so I thought I had better do another one, again.
 
Ramble
It's really not rocket science, honestly, and you really really don't need to jack any end of the van up, though, to me, logic says you would jack up the rear not the front! Water finds it's own level and all that, the radiator is the highest part of the system, so why would you jack the front of the van up and make the highest point even higher? surely thats making the problem worse, I never understood that bit me.
Why am I qualified to write this? Well, at the time of writing I have worked on these vehicles for 3 years professionally, I don't think there is a week goes by where I do not have some part of the cooling system in pieces and I have to bleed the cooling system. In those 3 years to press, I have never resorted to messing about with a jack. To me thats qualification enough that this system works, pending on you having a complete, sealed, pressure holding cooling system you can bleed it in 1/2 hour.
 
 
few bits of science you probably forgot from school.
 
You heat water, it expands.
You pressurise water, it raise it's boiling point.
You heat something in a confined space and you raise it's pressure.
You can compress a gas, you can't compress a fluid (much)
Water finds it's own level.
 
We're going to use these science bits to help us on the road to cooling nirvana.
 
parts in the system you need to know about.
 
Engine, the noisy thing in the back
Radiator, the big heavy thing at the front, 2 types, early 1.6D "CS" type with 2 switches towards the top, these are crap and if you even get the opertunity to upgrade to the later style please do. For some reason VW put the fan switches at the top of the radiator, if you have a leak and air is introduced into the system then coolant drops below the fan switches level, and they don't work! Well done VW for that one, clever boys.
Anyway, they soon realised the error of their ways and changed to a much better radiator, and they put the fan switch in a sensible location towards the bottom of the rad, much better.
The radiator, early CS or later style have a bleed screw at the top to let the air out, much like the ones on your radiators in the front room (unless your Welsh, but there are no 3 bar fires on a wedge!)
 
Header tank, the one INSIDE the engine bay, the one with the pressure cap, this must always be full right to the top, always, forever, period, fullstop.
 
header tank cap, Make sure your header tank cap holds pressure, there are a few types, the early push and twist ones (rubbish) the later screw on ones, these come in 3 flavours, Black, usually knackered by now, Blue with 2 visible round valves in the business end, usually knackered, and the best of all, the later blue ones with no visible valves, they also make quite an impressive "quack" noise if you blow down the spout. (025 121 321 B)
If you are in any doubt, replace it.
The only 100% reliable way to test a cap is with a pressure tester.
 
Expansion tank, the one behind the flap (heh, he said flap) the level of this goes up and down with engine temp, only time to set the level of this is when the engine is clap cold as it is the only constant you can get, run it for 5 minutes and the level may have risen.
 
Thermostat, usually open about 87°c, it stops coolant flowing to the radiator when the engine is cold to let the engine warm up quicker, once it reaches a preset temp it gradually starts to open and lets coolant flow to the radiator to cool it down.
 
Fan switch, turns the dirty great fan behind the radiator on at a set temperature, usually comes on at 87°c and goes off around 76°c the thermostat and fan switch do a really good job of keeping the temperature of the engine regulated, thermostat opens, coolant goes to the front, rad temp reaches 87°c, fan comes on, cools coolant, temp goes down, , thermostat closes a bit, fan goes off, engine warms, thermostat opens more,fan comes on, la di da etc, you get the picture.
 
Heater circuit, is like a minature cooling system, it has pipes, a radiator (heater matrix) and temperature for the heater is controlled by a remotley controlled valve (much like a tap)
 
 
Bleeding the system.
 
 
Lets presume you have a totally empty cooling system, say, you have changed the front to rear coolant pipes.
The T3 cooling system takes somewhere in the region of 16 litres of coolant, so for a 50/50 mix you need 8 litres of antifreeze.
 
First off, if you are filling a completely empty system, undo the bleed screw on the radiator, like we said earlier water finds it's own level, if you don't the job will take longer and you will use more fuel!
make sure heater controls for front and rear heater if fitted are in the hot position.
So, pour in neat antifreeze first until you can't get anymore in.
Close the bleed screw.
Fit header tank cap.
Start engine.
Remove cap, now pour as much coolant in as you can.
Once you can't get anymore in, rev the engine to 2000rpm ish.
The coolant level will drop, add more coolant till you can't get anymore in.
Keep revving, screw the cap back on, if you let go of the revs without the cap on and the level will swiftly rise and you will have just wasted a shit load of new antifreeze onto the floor, well done!
Okay, Got all your antifreeze in yet? You need to get that in first before you put any water in.
Go to the cab and give it a right good rev!, like a right good up to the redline rev!
Go to the radiator, undo the bleed screw and let some air out.
Go to the back, undo the header tank cap and add some more coolant, if the level has dropped a load, rev it to 2000 rpm again and get a load in till no more will go, cap on.
Go to cab, give it a rev, go to rad, let some air out.
Once you get to a piont where it feels like you can't get much more coolant in, then go to the cab and have a break, sit down for a minute and keep it revving at 2000 rpm to get it to warm up quicker.
To make it look like you really know what you are doing, flick the heater on and see if the heaters are starting to blow warm, for a real manly "I'm a mechanic me" look, set the heaters to demist and hold your hand above the vents, works great and if the missus is watching you may even get a brew out of that one.
If the heaters aren't even tepid yet, rev the nads off it again.
The heater circuit isn't controlled by the thermostat, so the heaters work regardless of thermostat position.
Once the temp gauge starts getting towards 1/2 way best let some more air out so let it idle.
Go check water level.
Top up as needed.
About this time I like to fill the expansion tank up right to the brim and attach the pipe from the header tank to the expansion tank cap.
Give it a rev, let some air out.
 
Now, listen to this bit, it's kinda fundamental as to how the system works.
The cooling system is meant to run at about 1 bar of pressure, thats about 15PSI in old money, that means that the coolant won't boil until about 115°c
So, the header tank is full to the brim, the cooling system reaches 1 bar and a valve opens in the cap and lets the excess pressurised coolant out into the expansion tank, the level in the one behind the flap rises.
once the engine cools, the coolant cools and contracts, if the system were to be totally sealed you would get rubber hoses collapsing, so inside the header tank cap is a second valve, a vacuum valve, this opens at some pressure or other (dunno that) and lets coolant from the expansion tank back into the header tank.
This keeps the header tank constantly topped up with coolant and no air in the system.
Right...
back to bleeding..
 
What we are doing here is warming the cooling system to increase it's pressure, we are using this pressure to expell the air trapped at the highest point by letting it out of the bleed screw.
easy really when you think about it.
When did you ever see your plumber with a acro prop under your house jacking it up so he could bleed the radiators?
You didn't thats why, so why should you do it on your van?
 
Right.
Where is the temp gauge? as we mentioned before, the thermostat and fan do a really good job of keeping the engine temps stable, from new the gauge should come up to half and stay there more or less, just over half fan should come on, just below half and the thermostat will start to close and bring the temp back up.
If at any point the needle goes over 3/4's you may have a problem.
 
Always run the engine up to test the cooling fan works.
 
With the engine running, cap on and pip to the expansion tank connected, i find it helpful to unscrew the cap with the pipe connected to let the last bits of air out.
 
Go for a good run
 
Come back.
 
Let some more air out of the rad, once it runs warm water with no bubbles it's done.
 
let it cool, check level when clap cold in the expansion tank.
 
If this doesn't work you are either stupid and havn't listened to the above or you have problems, possibly head gasket problems.
 
okay, pick that lot to bits then!!
 
 
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Direct Link To This Post Posted: 21 Aug 08 at 16:16
am i right in saying that the later t3's have a sort of self bleed system????
the thing is that i bled my van a while back and after i thought i got it right i went for a drive to notice the header behind the flap had emptied. so i filled it and used the van as normal checking the van every day or so and topping up as required.
after a few days it didnt go down anymore and she's been fine since.
 
 
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Direct Link To This Post Posted: 21 Aug 08 at 18:23
And am I right in saying that if the level in the expansion tank doesn't stop going down after a few days of topping up, (even if the header tank stays full right to the top, always, forever, period, fullstop) then you must have a small leak somewhere and obviously don't have a complete, sealed, pressure holding cooling system?  Cry  Question
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Direct Link To This Post Posted: 21 Aug 08 at 20:12
Originally posted by camowagen camowagen wrote:

am i right in saying that the later t3's have a sort of self bleed system????
the thing is that i bled my van a while back and after i thought i got it right i went for a drive to notice the header behind the flap had emptied. so i filled it and used the van as normal checking the van every day or so and topping up as required.
after a few days it didnt go down anymore and she's been fine since.
 
 
 
basically yes.
if there is any air left in the system it will work it's way to the top.
So, if it ends up in the header tank, after a few drive cycles the air will end up in the expansion tank and the level will drop as coolant from the expansion tank will replace the air in the header tank.
Like you say, it takes a few days.
If this is what you have done I would be tempted the next time you pull up outside with a warm engine to get out and just quickly check that there is no air left in the radiator as that is also the other "top"
 
This is why I say to customers when they leave after cooling system work to top up the tank behind the flap when the engine is cold.
 
It's not just later ones, they will all do this.
 
The time to worry is when the level in the tank behind the flap rises as that usually means the head gasket is knackered and combustion pressure is getting into the cooling system.
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Direct Link To This Post Posted: 21 Aug 08 at 20:13
Originally posted by Mooch Mooch wrote:

And am I right in saying that if the level in the expansion tank doesn't stop going down after a few days of topping up, (even if the header tank stays full right to the top, always, forever, period, fullstop) then you must have a small leak somewhere and obviously don't have a complete, sealed, pressure holding cooling system?  Cry  Question
 
Probably a leak.
best thing to do in that scenario would be to pressure test the system.
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Direct Link To This Post Posted: 21 Aug 08 at 22:35
Originally posted by Baxter Baxter wrote:


Fan switch, turns the dirty great fan behind the radiator on at a set temperature, usually comes on at 87°c and goes off around 76°c the thermostat and fan switch do a really good job of keeping the temperature of the engine regulated, thermostat opens, coolant goes to the front, rad temp reaches 87°c, fan comes on, cools coolant, temp goes down, thermostat closes a bit, fan goes off, engine warms, thermostat opens more,fan comes on, la di da etc, you get the picture.


Thanks for taking the time to write this post Baxter -very helpful :)

Am I right in thinking that some models have a 2-tier fan? I was told (when in France at the breakdown place) that it was a 2-speed switch that had gone tits-up, and was removed from the rad (on a 2.1 DJ).

Since that happened the temp warning light blinks constantly but she's done 2500 miles in 3 weeks like that so can't all be bad.
WTD, T3 -40mm springs, a poptop and someone to fit it :)

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Direct Link To This Post Posted: 21 Aug 08 at 22:49
There is always a 2 speed fan, 2 slightly different systems.
 
1. Early 1.6 D "CS" engine has 2x 2 pin switches at the top of the rad, one switch does low speed, one switch does high speed.
 
2. Later, normal most popular style is the 3 pin switch which has one commin supply terminal then depending on the temperature depends on which terminal is made live to operate each speed on the fan.
 
The fan in both cases is shunt wound to achieve 2 speed operation.
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Direct Link To This Post Posted: 31 Aug 08 at 09:29
Cheers, just what I needed to know. Dropped a hose connector during the week and need to represurise. Sounds like I didn't give it enough wellie
 
I've got another bleed valve (or at least that's what Haynes call it) inside the engine bay - I let this out whilst bleeding system. Is it not necessary?
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Direct Link To This Post Posted: 31 Aug 08 at 15:14
yep, I've ommited that bit, all the petrol engines have a small bleeder valve, on the earlier ones it's the plastic valve to the left of centre of the engine bay joining the 2 rubber hoses together, and thre metal pipe over the engine, best to open it for a bit until the uppermost pipe is felt to be warm,
On later engines it's on the thermostat housing cap, again, undo it once the engine is warm and wait till you feel the pipe go warm, this tells you coolant is passing through it and not air!
:)
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Direct Link To This Post Posted: 31 Aug 08 at 15:35

Simon will probably disagree with this, but I have never liked thermostats that don't have the bleed hole in the upper ring. I have a drilled a 3/16th hole and this allows coolant to fill the radiator and into the engine block the instant you switch the engine on.  It takes slightly longer for the engine to warm up and it runs at a slightly lower temperature which is exactly what I want for LPG. The van drives very sweetly too and the economy has not been affected, in fact it is better on LPG!  Bleeding the system is far simpler now as the radiator immediatley fills to the brim and I don't get any air locks in the thermostat housing. I still run it to full temp. and beed is as per instructions supplied by Simon.



Edited by AngeloEvs - 31 Aug 08 at 15:42
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Direct Link To This Post Posted: 31 Aug 08 at 18:49
Some thermostats have a "Jiggle pin" for the same reason.
They were never fitted to the t3 though.
I have done it in the past, but you shouldn't really need to.
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Direct Link To This Post Posted: 11 May 09 at 13:41
Baxter

Just had to replace water pipe on my 1.9 in a hurry - failed just before I was due to set off for Vanwest. After reading pages of conflicting and frankly worrying stuff on the Club 80-90 forums - jack front up, jack back up, change thermostat a couple of times etc..... I was not looking forward to bleeding the system, but stumbled accross your post, thank goodness. Printed it out, followed it to the letter, no jacking up, no problems. Worked a treat, heater worked first time, no cold pipes, thermostat opened, rad got hot, fan cut in when it should - job done. The run to Vanwest was 50 miles - no drama on way there - van ran perfectly fully loaded, all temps normal: great weekend.

Thanks for this post! It cuts through all mystique on the cooling system on these vans. I will now spread the word to whoever asks...

Cheers, Oldjets
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Direct Link To This Post Posted: 03 Feb 10 at 19:23
I never had much trouble filling my t3 with coolant - and had to do it several times due to some crap head gasket water seals from GSF which lasted 1 month and 2 months respectively, I put them on as I bought the van with known cooling issues. I replaced one in a festival campsite in wales, which drew a small crowd, which was slightly embarrasing when I forgot to re-connect the distributor.. Funnily enough after that the engine didn't break again!
Anyway - the way I did it, after reading all the mad ways then seeing what actually worked, was to open the bleeder on the radiator and in engine bay, heater to hot, fill the header tank. Start engine, keep adding coolant till it comes out the radiator, revving as necessary to get it to suck it up, close bleeder. Top up tank, rev, top up tank, repeat till it takes no more, screw cap on, fill expansion bottle. Done. It didn't suck much more in after. Takes about 20 mins at most. Maybe mine was easier than most, it wasn't difficult. The water pump in mine was pretty powerful. Was harder than my t4 - that's a doddle..

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Direct Link To This Post Posted: 02 Aug 10 at 11:10
Does it matter if the bleed valve in the engine bay won't open? My early style valve is buggered (oooeeerrrr)
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Direct Link To This Post Posted: 02 Aug 10 at 18:35
You might have a job letting the air out if the bleed valve is shut Wink Better to sort it out while you`re in there.
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Direct Link To This Post Posted: 02 Aug 10 at 19:02
he's still got one on the radiator so i would of thunk it'll be rite!
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Direct Link To This Post Posted: 02 Aug 10 at 19:10
I would sort it  if I could but the bleed valve is the old early "rare as rocking horse shit" type.
 
The slot that used to allow it to be opened with a flat screwdriver is buggered
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Direct Link To This Post Posted: 03 Jan 11 at 17:04
took my van for a run today...first time in over a month.
 
i need to change / renew my antifreeze...so was reading up on "how to bleed the system"
 
Mr Baxters info says that the tank in the engine bay should be full to the brim.
 
mine is ..and always has been (i think) only full to the seam ....
when Mr B says full to the brim....does that mean ...literally ?
 
also
 
is it best to drain the whole system to empty...then add new stuff.
or to drain half out and replace with fresh antifreeze.
 
where is the best place to drain from...do you just pick a hose that you can get to...and remove it.
 
(i wish i could understand even a little bit of this mechanicalisatyion stuff)Embarrassed
 
thanks ...keith


Edited by niko - 03 Jan 11 at 17:05
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Direct Link To This Post Posted: 03 Jan 11 at 19:43
And a very important point is fit a vw (if available) or decent supplier temp gauge sender (I resort to them Brickwerks cowboys)!
FIT A GSF or any of your local motor factors ones it will fit but be WRONG and show overheating!!
I muppetly listened to factor people n few other people an got thru 3 senders recently and it was only after fittin the Brickwerks one it cured a (non existant)problem where I had stripped the whole water out lookin for a non existant overheating problem!! Lesson learnt for me don't be a muppet too! LOL
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Direct Link To This Post Posted: 03 Jan 11 at 20:12
I've got issues in my cooling system too :(
 
Overheating, pressurising, blowing header tanks... but the radiator never seems to get warm; it does let me bleed stuff out of the radiator though (but the hottest it ever gets is lukewarm!) - and the heater matrix has now started leaking :(
 
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