A question to those of you out there using the crossflow lump.
I have replaced the 'normal' thermostat housing with one with a filler cap and thermoswitch take off.
I needed to do this because the rad filler cap is significantly lower than the thermostat hosing and I could not fill / maintain the coolant level.
I now fill the coolant with the rad cap off until that overflows, replace the rad cap and continue to fill until it is half way up the neck of the new
filler on the thermostat housing.
The problem is when the engine gets hot the coolant expands and there is nowhere for it to go so some is forced out of the filler cap, when it cools
the level is below the thermal switch and often the thermostat itself is left high and dry. The system is not losing the coolant from any other
place.
Incidently the cap on the rad is a high 'pound rating' than the one on the Thermostat housing so in theory it should never let water
past.
I know I need an expansion tank but the problem is where to put it? I cannot find a place higher than the thermostat housing filler as it is quite
close to the underside of the bonnet. if it is lower then it will not fulfil the purpose of ensuring the engine is always 'full of
water'.
What have you done to get around this problem?
- Alan
I would replace the old Thermo housing but have a 6mm OD pipe welded into it.
Put your expansion bottle on the bulkhead and plumb the large pipe into your lower rad hose (you will need a tee) and the 6mm hose from the thermo
housing into the small pipe in the expansion bottle.
As long as your expansion bottle is at least level with the top of your water system then it will work ok.
I think your problem is more to do with an airlock.
Your thermostat is closed when you fill so air is getting trapped in your engine block.
Drilling a small hole in the thermostat will help let some of the air out and aid filling.
[Edited on 9/4/2007 by nitram38]
Alan
This may / may not help as I plumbed in my ZZR and not a Xflow, but this is what I have found.
My thermostat / filler cap / temp sender is an all in one unit, mounted hard up against the underside of the bonnet, just behind the nose cone. This
is the highest point in the system. The cap has a spring in it, which as the water / coolant expands pushes the cap part way up. The coolant then
flows out of a small 4mm pipe which is linked to the bottom of the expansion bottle (mounted on the bulkhead, but lower than the top of the system).
The expansion bottle is not pressurised and has an over flow to underneath the car.
As the system heats up coolant expands into the tank on the bulkhead. As the system cools down it gets sucked back into the system via the cap.
It doesn't seem to matter that the bottle is lower than the thermostat.
Hope that helps.
Mike
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I ve done similar to the system nitram suggests but instead of teeing into the bottom hose I teed into the heater return to the water pump . I have an expansion tank on the bulkhead but my thermostat housing does not have a filler , it has a bleed off pipe that goes to top of header tank . If I have to fill system from scratch I always remove stat and fill until water comes out of stat hole, refit stat and housing , fill until full. Drilling a small hole in the stat would have the same effect but I find my system works . Never have any problems overheating Think I got the plastic tee piece from a pinto engined Granada?
Try reading this.
I do my x-flow this way - works perfectly. I think he's discussing Pintos, but the principle is general.
quote:
Originally posted by Guinness
My thermostat / filler cap / temp sender is an all in one unit, mounted hard up against the underside of the bonnet, just behind the nose cone. This is the highest point in the system. The cap has a spring in it, which as the water / coolant expands pushes the cap part way up. The coolant then flows out of a small 4mm pipe which is linked to the bottom of the expansion bottle (mounted on the bulkhead, but lower than the top of the system). The expansion bottle is not pressurised and has an over flow to underneath the car.
As the system heats up coolant expands into the tank on the bulkhead. As the system cools down it gets sucked back into the system via the cap.
It doesn't seem to matter that the bottle is lower than the thermostat.
I may be sounding a bit thick here, but how does the water get sucked back into the system if the cap on tht thermostat cover is sprung.
Surely the spring is there to allow for release of water under pressure, but then the spring closes - it's a 1 way valve. The best method would
be to have a pressurised header tank.
BTW my crossflow doesn't have either. It does suffer from a little expansion if full, but the fan stat is in the radiator so it doesn't
matter - never overheated yet in 3 years (and I've been to some pretty hot places).
It does work with an ordinary cap but not as good as a pressurised system.
That is why modern cars now opt for the pressurised system.
Why re-invent the wheel?
One tip though, I use a bottle with a float level switch and an indicator light on my dash.
This is because the k-series I use actually reads a normal temp when water is lost so I don't have an early warning.
Also being rear engined, I cannot see any steam etc.
quote:
Originally posted by Marcus
I may be sounding a bit thick here, but how does the water get sucked back into the system if the cap on tht thermostat cover is sprung.