Currently I'm having some problems with overheating of my x/flow.
I'm still sorting this out and i was reading some posts of members who have the same problems.
Multiple times I read about people who advised to connect the heater outlet (inlet manifold) to the connecting just before the water pump.
After thinking about this, this looks to me as a big mistake. The hottest coolant (in the top of the engine) is routed directly (and still very hot)
to the inlet (water pump). As this is a flow what is less restricted thus has less resistance than the radiator route the full flow capacity of the
hose is circulated hot through the engine.
With a original heater system installed this isn’t the cases because the coolant is cooled by the heater radiator, and is restricted with a valve for
adjusting the temp in the car.
So in my opinion the best way is (if you don’t want to have a heater in the car) to block the heater hoses so the full flow of coolant is going
through the (main) radiator.
Well this is my opinion.
How do you guys think about this????
(Sorry for my bad English. I’m from the continent)
Makes sense to me
You MUST have the bypass connection connected or the thermostat will not open and the engine will overheat also the coolant will not circulate within
the cylinder block and head.
1970s Fords didn't use a water valve on the heater. coolant circulates continuously through heater matrix which was kept contiuously hot,
heater air output temperature was controlled by air flaps mixing warm and cold air.
You can however restrict the bore of the by-pass hose from 19mm down to 12mm by fitting a restricter with the pipe work.
[Edited on 22/12/05 by britishtrident]
the way you have it is the only way,there are only 2 conexions.
is the rad below the level of the thermostat housing?if so the stat is prob dry,fitting a header tank via a T peice into the return to the water pump
is a good idea
I'd check for airlocks and correct timing first.
The latter is normally the problem on a crossflow...
Can we take a couple of steps back.
Over heating - how do you know this? You getting steam out or you trusting your guage? Are you able to measure water temp?
And what are the conditions it over heats? Happens at idle, slow traffic, fast traffic? Air temp?
A brief description of you cooling system would help; radiaotr (origing or size, fan(s), thermostat rating, how is fan controlled).
I have not delved in any detail but from what I can see on miy xflow the thermostat outlet goes to top of radiator and lower radiator goes to water
pump (I have no heater plumbed in - still to find where that is connected).
Have you checked timing is correct? Thermostat is working - esyu to test in a pan of almost boiling water? Is connected right way round? Radiator
core is not blocked?
etc.....
I'm also thinking of an airlock or the timing.
The engine is really running hot. When driving in the city eventually it pisses out all water 
. when driving very steady 50mph it's oke and
the temperature is about 100 C ..
The top of the radiator is above the thermostat housing, so an airlock can't be it.
The thermostat itself is working but momentairly not installed.
The temperature meter i have calibrated in boiling water, so this should give me a indication.
So i'm thinking of the timing.
That's why i'm now soldering a megajolt 
But i'm still thinking that such a bypas from the inlet manifold to the pump i'sn't a good idea, because you will only circulate hot
water.
britishtrident posted on 22/12/05 at 11:34 AM
You MUST have the bypass connection connected or the thermostat will not open and the engine will overheat also the coolant will not circulate within
the cylinder block and head.
This heater circuit doesn't has anything to do with the thermostat?? or does it?
quote:
Originally posted by phaeton
The engine is really running hot. When driving in the city eventually it pisses out all water
After doing the timing of the ignition and it is still overheating, i maybe have to look atthe water pump.
Rescued attachment cooling system.jpg
Head gasket failure?
At the very least it would be a good idea to run a hose from the blocked heater outlet to the water pump inlet . I t may also help to tee off from this pipe and fit a header tank, this should allow any air to find the highest point of the cooling system and help bleeding . Head gasket failure may show up as bubbles in the header tank or get system tested with block tester (kit with a liquid that changes colour if combustion gases are present in cooling system )
Air locks really messed me up as well, in my early Locosting days. Boiling over into the overflow tank, and similar nightmares. Took 3 or 4 fills
before it stopped mucking me around - since then it's run for 1000 miles without any problems, rarely going over 90C.
As stated - connect a hose between the two heater connectors. You also need an overflow tank, or a pressurised header tank. If you include a T-piece
in that heater hose, you can add a pressurised header tank as well. Although you will have to have a vent at the highest point in the circuit
(usually the thermostat cover).
David
bad news!! your system look fine to me even with the heater out of the circuit.
also as your radiator filler is atthe highest point, you should not have air locks.
dunno what else to sugggest
:
re: head gasket - you would see get water coming out of the exhaust and the water system would get pressurised.
like alwsys, start with the simple/cheap things like getting the dye to test for h/gasket failure, replace radiator cap, and fit small hose to bypass
the heater i.e. complete the circuit that you have blocked off.
then cry!
For the sake of a couple of minutes work and a gasket when I filled my cooling system for the first time I removed thermostat and filled header tank with a 50/50 mixture of water and antifreeze until water ran from thermostat hole . Then fitted the stat and finished filling system , this helped to bleed most of the air from the system and so far has been fine
like wot he said ^^^^^
maybe worth tilting the front as high as possible when filling up?
Not rocket science
The bypass circuit is ESSENTIAL on all cars with a thermostat the reasons are simple without it the thermostat is not getting any circulation round
the bulb and hence the thermostat remains closed until the engine is well on its way to overheating.
It also prevents hot spots forming in the head and over cooling of the lower part of the cylinder block.
In addition to the above the flow it provides it prevents cavitation in the water pump when the thermostat is closed.
[Edited on 22/12/05 by britishtrident]
^^^ What he said!
You'll see this even on healthy engines, water is a byproduct of internal combustion. That's why there's hydro in hydrocarbons.
There isn't coming water out of the exhaust nor white smoke. That's why i will leave the head gasket for what it is for now. First i'm
going to sort out the ignition (just finished soldering my megajolt ) and then look further.
I'm still not convinced about the heater plumbing.
When blocked (as in the drawing a few posts ago) is this the sequence of things that happens:
1. The motor starts (termostat closed) and the combustion is warming up the water around the cilinders. There ISN'T a flow going because the
thermostat is closed. This isn't a problem for the waterpump because this is a flow pump and not a pressure pump (i don't know the right
english name for it) so it will spin in stationair water.
2. All the water within the engine will graduatly warm up all the water including the water under the termostat because water is a good
thermoconductor (thats why we use water, and the price and availibility of course).
3. When all the water is over 85 degree (or something like that) the termostat opens and the coolant will circulate (and cooled by the rad) and there
will be cooler water given at the water pump.
4. the cooler water will be at the bottom (because this is denser than hot water) and will push (with help of the pump) the hot water out at the top.
This will be by the thermo stat as this is the only exit.
When connecting a bypass there will be 2 exits (thermostat and heater exit) and will the water choose the exit with the lowest resistance. As the
themostat opening is not that big and a odd shape the water will goes through the heater exit. Also the rad and long hoses will add to this
resistance.
This hot water will be offered at the water pump. And will be pumped in the engine.
So i think the biggest cooling capacity will be when the heater in and outlet will be blocked.
Please tell me if I'm totally wrong.
Sorry for being so subborn
I will give it a try after the holidays, the bypass tube, and look if it will improve. I am curious about it.
For what a length of heater hose costs I would have thought it worth a try ? If it doesn't improve things it's not the end of the world but if it works you have a result. Just my opinion of course.
Actually water isn't a very good conductor of heat. It is a very good heat transfer medium but not by conduction.
I woud suggest a Polo rad and expansion /fill bottle from something like a rover 25/45. I had this truble with a basic system, but with the above setup I anm now having to block of some of the rad to get to temp
quote:
Originally posted by britishtrident
Not rocket science
The bypass circuit is ESSENTIAL on all cars with a thermostat the reasons are simple without it the thermostat is not getting any circulation round the bulb and hence the thermostat remains closed until the engine is well on its way to overheating.
It also prevents hot spots forming in the head and over cooling of the lower part of the cylinder block.
In addition to the above the flow it provides it prevents cavitation in the water pump when the thermostat is closed.
[Edited on 22/12/05 by britishtrident]
I now have finished installing my megajolt.
The engine without thermostat and bypass is heating up to 60 degrees celsius.
It seems that the dizzy was faulty and had not enough advance.
Regards Erik
[Edited on 7/1/06 by phaeton]