David Jenkins
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| posted on 14/2/05 at 08:26 AM |
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Water-ejecting crossflow
Rather than hijack the overheating crossflow thread...
My crossflow is running well on super-unleaded (it's been converted), timing set to 10 degrees BTDC, no pinking on acceleration, max temperature
on the gauge is 95 degrees C and the fan comes in when it should.
My water system is very simple - engine block - fiesta thermostat housing - top of polo radiator - bottom of rad to water pump. An additional hose
goes from the inlet manifold to the extra inlet on the water pump input. Overflow is taken to a reservoir and sucked back on cooling.
The trouble is, it's started pushing a lot of water out into the overflow tank, to the point where it's ejecting out of the top.
It's not being pushed out by a gas leak in the engine, because when the engine cools it sucks all the water back and the system's full
right up to the cap.
This has only happened since the last rebuild and coolant re-fill. It could be an air lock, but the engine was run fast when running in the cam, and
I've done 20 miles on the road, so I would have thought it would have cleared by now. The water and oil show no sign of contamination.
Any suggestions? If it is an air-lock, any good tips to get rid of tricky ones?
David
[Edited on 14/2/05 by David Jenkins]
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britishtrident
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| posted on 14/2/05 at 08:32 AM |
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Sounds very much like trapped air is the pressure cap at the highest point of the system ?
but check the mechanical advance is working freely and has a tny ammountof lubrication to stop it from sticking also check the thermostat has a tiny
anti-airlock hole.
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David Jenkins
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| posted on 14/2/05 at 08:34 AM |
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Yes - the cap is at the top of the system
Yes - the thermostat has a little hole (I put it there  )
I haven't checked the advance... job for tonight, I guess.
David
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Peteff
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| posted on 14/2/05 at 10:41 AM |
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Run the engine at a fast idle with the cap removed till it gets hot then squeeze the top hose while it's still running. It usually clears my
pinto when I get an airlock. I can get another pint of water in after, don't know where it all goes though.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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David Jenkins
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| posted on 14/2/05 at 01:26 PM |
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Have you found that your socks are wet after doing this?
David
[Edited on 14/2/05 by David Jenkins]
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stevebubs
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| posted on 14/2/05 at 03:22 PM |
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A fe wthings I found useful for removing air from the cooling on my xflow.
1) Get a thermostat housing with a removeable top - either pressuce cap blank or fan switch (mine was from an 1100 Mk 1 Fiesta)
2) Ensure the Rad has a bleed screw at the top
3) "Pump" by hand the coolant lines with the thermostat housing and overflow tank open, then re-fill from the thermostat housing if the
level drops
HTH
Stephen
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Dave Ashurst
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| posted on 14/2/05 at 04:24 PM |
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Dave,
Where does your expansion overflow draw from? (Hopefully from the highest point in the cooling system from where it can vent any accumulated trapped
air.) The radiator cap is not the high point I guess?
If it's not venting from the high point then a much better & safer method, in my opinion, is to do away with the overflow/expansion tank and
have a cooling system with a header tank at the high point. A vent pipe from the themostat housing to the top of the header tank keeps the waterways
air free.
Otherwise it seems to me you will be forever doing what stevebubs suggests above - i.e. venting the trapped air (like we do from our back bedroom
radiator, which seems to be the high point in our heating system! Luckily the consequence of air in the top of a central heating radiator is not a
potentially overheated cyl. head with siezed valves.)
regards
Dave
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David Jenkins
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| posted on 14/2/05 at 08:06 PM |
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I have the Fiesta thermo cover, it's at the top of the system, and that's where the rad pressure cap lives. The overflow pipe goes from
there to the catch bottle. My Polo rad doesn't have a cap of its own.
Problem at the moment is that it's persisting down outside, so I can't try some of the solutions offered...  It's a bit of a noisy
thing to do at night in a quiet village cul-de-sac as well!
I'm considering a pressurised header tank, but I was hoping that I wouldn't have to do it in the near future... maybe I will now. Any
good sources for a suitable tank?
David
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Marcus
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| posted on 14/2/05 at 08:12 PM |
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David, as a matter of interest (to me anyway) why have you used an expansion tank? My crossflow doesn't have one, and doesn't appear to
need one. The cooling system is designed to be pressurised, which makes the water boil at a higher temp. If you have an open vent, the water will boil
at a lower temp and you may find it CAUSES vapour locks.
Marcus
Marcus
Because kits are for girls!!
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David Jenkins
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| posted on 14/2/05 at 09:03 PM |
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Marcus,
What I've is pretty much what the crossflows always had - a pressure cap (13psi) that keeps the boiling point higher than normal, with an
unpressurised tank to catch the overflow. When the engine cools the vented coolant is sucked back in. There's a special rad cap that allows
2-way flow as appropriate.
This worked perfectly well for 200+ miles before I had to rebuild the engine, but I think I must have ended up with an air pocket when I re-filled
it.
Thinking about what people have suggested, I don't think it's anything to do with overheating (due to timing, advance, or whatever) as I
kept a close eye on the temp guage while this was going on - it didn't go over 95C, which is the correct working temperature.
David
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