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Overheating crossflow
Mad Scientist - 4/12/03 at 10:56 AM

Crossflow overheated last night. It blew the water pump gasket. Question is why? I think it may have been an air lock, but i'm not sure. Whats the best solution for air locks? Fiesta thermostat housing or header tank?

Cheers.

locoboy - 4/12/03 at 12:14 PM

I dont know about the best solution but for identification of the problem i would fit (even if a temporary arangement) an expansion tank so you can see what is happening with the coolant ie bubbles, expansion / contraction, and by how much and at what temperatures.

I have struggle with my pinto to get the expansion bottle high enough to be Really effective, i dont have an over heating issue but had to put in an aditional bleed point in the system to purge it of air.

David Jenkins - 4/12/03 at 12:30 PM

When I first ran my crossflow I had serious overheating problems, almost entirely due to an air lock directly under the thermostat. The thermostat never opened because the water wasn't touching it, so the air lock never cleared. After taking advice from members of this forum I drilled a small hole near the rim of my thermostat so that I could be sure that the wax cartridge was always under water (the air trickles out through the hole, into the radiator cap chamber in my Fiesta 'stat housing).

You will need an expansion tank of some type - either the pressurised type as found on modern engines, or an overflow bottle as originally fitted to crossflows (which is what I'm fitting). As the water expands the excess goes into the expansion bottle. When the engine cools again the 'lost' water is sucked back into the cooling system.

Alternatively, how old are your hoses? It's not uncommon for the inner part of water hoses to collapse and block the system.

Hope this helps!

David

Cazzy R - 4/12/03 at 01:23 PM

Hi.
IME the best arrangement is to use the Fiesta thermo housing which has NO FILLER cap and a pressurised expansion tank. The radiator should preferably also have NO CAP failing that use a a cap that seals and does not blow off when the system is pressurised.
There should be only one point of pressure relief, at the highest point of the system i.e. at the expansion tank.
The tank should be the type that has a water inlet at the bottom and an air bleed inlet at the top.
The bottom cnnection should be teed into the bottom radiator hose and the smaller air connection piped to the NO CAP Fiesta thermo housing.
Make sure the header tank is as high as possible and that the water level is above the top of the thermo housing.
Have a look at a Valencia powered Fiesta MK2. to get the general idea.The tank is the ideal design for function but probably not the best for a tidy layout.
Small holes in themo flange is a good idea.

Hope this helps.

Dick Axtell - 5/12/03 at 08:25 PM

Hi Dave (& CazzyR),

Please explain difference - Mk2 Escort vs Fiesta thermo caps. My existing 1600GT xflow t'stat housing has no blanking plug inserted into top (as per other Ford examples).

TIA
Dick Axtell

JoelP - 5/12/03 at 09:26 PM

my system as it stands is a 1600 pinto all standard, has a tee from the top hose to the expansion tank. what is the purpose of the blocked off tube that comes out of the t'stat? is it any use in a kitcar environment? thanks in advance...

Stu16v - 5/12/03 at 10:29 PM

quote:

Crossflow overheated last night. It blew the water pump gasket. Question is why?


Because it did? Sometimes, these things happen, sometimes without reason. Unless the engine has had previous history of overheating problems, why suspect another problem? Just change the water pump gasket, and see what happens.
But Cazzy R says is important, especially when the radiator is quite often situated lower than the engine. Fitting a carefully mounted and plumbed expansion tank allows this to be the highest point in the cooling system, preventing water blowout and naturally bleeding out any trapped air in the system. Even if your cooling system has never given you trouble, consider Cazzy's example as a worthwhile upgrade....

HTH Stu.

Cazzy R - 5/12/03 at 10:42 PM

quote:
Originally posted by Dick Axtell
Hi Dave (& CazzyR),

Please explain difference - Mk2 Escort vs Fiesta thermo caps.


In the Mk2 Escort the of the radiator was the highest point of the cooling system and therefore the logical position for the air gap & pressure release valve (the cap). Because of this the system does not need an artifical high point (header tank).
The styling of the Fiesta dictates that the top of the radiator is below the engine (like a locost) which means that if you were just to fill the radiator up too the max the cylinder head water jacket would be full of air. NOT GOOD! So a header tank is added high up in the system to raise the water level and ensure that the air gap is safely in the tank and not in the engine.
The Fiesta thermo housing has a small dia. tube protruding from it which should be plumbed to the top of the header tank (the air gap) so any air collecting in the thermo housing is bled back to the tank. It also has the top hose connection facing forward rather than back like the mk2 Escort. Not having a header tank the Escort item is devoid of bleed tube.
There are 2 types of Fiesta thermo one with the cap (mk1 XR2) and one without.
The cap is a handy fill point but you must use the correct cap not a conventional radiator cap which will allow air IN to the system. NOT GOOD. Far better to go for the basic version, no problems, and 10 a penny in the scrappies. Oh yes both Fiesta versions come with a electric fan switch.

I think that satisfies Dick's & Joel's queries.

Mad Scientist - 6/12/03 at 08:25 AM

Thanks for all the help guys. I'm going to get to the scrappy and find a header tank. Not sure how I can get rid of the pressure cap on the rad. though. Any ideas?

Pete

Stu16v - 6/12/03 at 09:48 PM

quote:

Not sure how I can get rid of the pressure cap on the rad.


Easy enough. You can either take it to your radiator repair centre and get them to remove the cap and neck and solder a plate over it. As the radiator is very often fitted on a tilt, on my current car I also soldered a bleed pipe into the highest point in the rad, and plumbed it back to the header tank so air cannot be trapped in what now becomes the highest point.

All this is assuming that you have a rad with 'copper' end caps of course....
HTH Stu.

[Edited on 6/12/03 by Stu16v]