Could anyone give me any tips (conventional or unconventional) on bleeding air locks from the cooling system?

Feel reasonably sure there are no head gasket issues as no bubbles with the cap off when running (hot or cold) and not losing coolant.
I have been bleeding (massaging top hose) most mornings for a couple of weeks now. Suspecting it was drawing air in on cooling down, have double sealed suspect hoses with cable ties and resurfaced the sealing surfaces that mate to pressure cap. ('Barrs Leaks' may be the next step but I would rather not use it if possible)
The pressure cap is not the highest point in the system - above it is the top hose and front heater matrix.
Begining to wonder if I should fabricate some sort of header tank in place of the cap, and let it idle for half an hour. As the top hose is pressured when hot I feel steam build up in it is preventing good flow through the rad thereby preventing the viscous from operating efficiently.
There is evidence of grease departure fron the viscous bearing - unless of course it is silicone loss - its operation does deteriorate when the top hose is pressured.
Vehicle is Hiace Supercustom but I think the cooling system is much the same as Townace.
Any tips would be much appreciated -
Chris
- (#9891) chris turner, 5 Aug 03 4:47

I'd guess the viscous coupling is faulty, Chris. Shouldn't leak...
Re the bleeding, I know that some Citroens and Pugs (ZX/306 etc) have the header tank on the side of the rad, below the level of both head and heater matrix. Haynes advocate rigging up a header for them- cut the base of an oil bottle and seal to the tank with an "O" ring around the neck.
But I wouldn't worry so much about a little air. As the system is under pressure, the water pump will circulate regardless of the top hose having a little air. Remember that older cars like the Mini, pre- expansion tank, always had air in the system, as the rad was never filled...

- (#9892) david miller, 5 Aug 03 9:32

Thanks David - tried the oil bottle trick and it worked in a jiff with some hand pressure (fiesta top suspension bush as the seal).
Then for the sake of it - drilled and old pressure cap out - fitted spacer and seal in cap - ran some rubber tube through the drilled cap of a (hienz) baby juice bottle with the bottom cut out and suspended upside down from engine cover - a more involved version but should allow unattended idling to allow any air that needs to to come up.

Re
fluid coming from bearing - ordered a new viscous at £171 uk. Found that when you burn lithium grease off a piece of stainless... it more or less burns off - but when you try it with silicone fluid (Wickes plumbing lube)... it leaves a wrinkly silicone skin.
Wondering if the fluid was silicone or bearing grease I scraped some of the fluid from around the viscous bearing and tried heating it... and it left a wrinkly skin!
Hence the order.. here's hoping that will be the end of the multimeter monitoring the temp...

- (#9893) chris turner, 7 Aug 03 7:36

Well, half an hour before picking it up, got a call it would be 10 days minimum.
Looking at the coupling it may be possible to lock it in sync with the pulley (dodgy I know but, necessity being the mother of invention etc.)
Had a few ideas - instant metal (not removable).
Putting a strip of steel under a pulley bolt and twisting it into the coupling fins.
Worm drive hose clips on the pulley shaft securing a strip of steel bent into the fins - or hose clips on the pulley shaft securing a strong cable tie through the small gap between fan and coupling.
Obviously, none recommended, just thoughts - as any of these letting go could fly into something and probably cause damage.
Has anyone any experience of such 'get you home' tricks which may last a couple of weeks of light use?
+ may locking the coupling actually seriously overcool the engine?
- (#9894) chris turner, 8 Aug 03 15:12

Chris. As you have ordered a new V coupling, is it worth taking the old one off and checking the fluid content? You can adjust the reed valve (look at my pictures)to give "too much" fluid at lower revs and still retain some modicom of "slip". I should think that many fluids (Wykes plumbing lube) would do to increase the fluid volume. After all, I don't think that the silicone fluid is a really special product,ie, it does not magically stiffen when heated, it's the volume of fluid, at particular temperatures, which are allowed into the outside drive chamber, which, in turn, drive the fan. As you have another coupling on order, you could seal the two halves with jointing compound sloshed over the seal ring, and that should last you the ten days or so

- (#9895) John Davis, 8 Aug 03 15:37

DON'T lock it- the fan will overspeed, could be catastrophic!

John, the fluid IS critical, silicone is used because of it's properties in shear. Look up info about viscous couplings for 4x4 and you'll see what I mean...

- (#9896) david miller, 8 Aug 03 16:16

Thanks guys,
Well I had the fan off and was considering drilling through the coupling housing and running a bolt through - glad I checked here first - now you mention it, there was a case of a driver killed in one of these roadsweeper machines due to the fan shearing and coming through the cab.
Looks like I may be running the rear heater 'full on' and ducting the heat through the rear window for a while.

- (#9897) chris turner, 9 Aug 03 6:16

Thanks David, Yes, I was a bit casual with my description of the fluid and, of course, it does have to have more properties that those required to drag the rotor around but, I was thinking more of some sort of drive, on a very temporary basis, for Chris over the next ten days or so. Do you happen to know if the silicone fluid is supplied as a a re-fillable part ?

- (#9898) John Davis, 9 Aug 03 7:10

It is, there's a website with info on part no, and how to rebuild the coupling. I believe that I've posted it in the past so check on Ace Answers, but have a search, it's on the web somewhere. If I trip over it, I'll post again

- (#9899) david miller, 9 Aug 03 8:53

Ah- HA!
http://www.nichols.nu/tip482.htm

- (#9900) david miller, 9 Aug 03 8:58

Thanks for your time and trouble David. That site is really interesting and has spurred me on to try to renovate the spare coupling which I have

- (#9901) John Davis, 9 Aug 03 9:32

Could be the 'beginings'of a small business there John!
After making a number of calls, concluded there's certainly a gap in the market.

- (#9902) chris turner, 9 Aug 03 16:41

Well, replaced the viscous and no improvement - did note however that on the old one - if held still until everything hot would try its hardest to pull at 2000-2400rpm - when it hit 3000rpm ... nothing. At idle it would pulse gently. The new one.. well I think it would take my fingers off if I tried stopping it... so that and the fluid coming from the bearing makes me feel ok about the expenditure to replace.
Now get ready to laugh - the multimeter I have been monitorng the temp with seems to have recalibrated itself - so all that worry was unnecessary. A pan of boiling water was reading 110c - so the bus was running at perfect temps all along. So a case of 'a solution looking for a problem' maybe.
Anyway, if anyone owns a 'Clarke' multimeter with a temp probe - the calibration preset is the one in the middle at the bottom (once case split).
Thanks to everyone for support - also re
increased height bleeding - Sealey do a leakdown kit - included is a pressure cap with a hose connector fitted - this cap if obtained as a spare part from the autofactors should be a good base for any homemade bleeding system

- (#10296) Chris turner, 16 Aug 03 12:04

This silicone fluid is in fact quite a speciaal stuff.
I believe it is what is referred to as a "non-newtonian fluid" (I think that is right), which basically means that as you mix it, it gets stiffer, then returns to it's former liquidity when you stop mixing it.
A solution of cornflour and water does the same thing. If you make a fairly thick mix of this, you can stir it slowly with great ease, but if you try to mix quickly you will feel great resistance.

I'm not sure how the heat is involved, but I think it is to do with the 'mixer' part of the mechanism.

When the liquid gets too low it simple doesn't have enough liquid to thicken enough to give the resistance to turn the fan.

Viscous differentials also use this method - the wheel trying to spin makes the liquid thicken on 'that side of the diff', and forces the drive into that side.
(I am sure there are many technical deficiencies in this description, but it is basically correct - I think)

Don't put anything else in there, you will only contaminate the fluid.

Dave

- (#10297) DaveW, 18 Aug 03 0:40