OK - now that my engine's running, it's getting too hot. After running for 5 minutes or so, the temperature gets up to 100C and water starts venting out of the pressure cap overflow like there's no tomorrow. The engine block is hot (obviously), but the radiator is cold - the top hose is cold, and the bottom one is starting to get hot from the pump end. The water being vented isn't particularly hot.

My guess is that water expansion in the block is pushing water back up the rad and out of the vent.

For those that don't know, it's a 1660 X-flow. The plumbing is very simple - hose from bottom of rad to the pump, and top of the rad to the thermostat housing/pressure cap. One other smaller pipe from the secondary pump connection to the inlet manifold connector. No auto choke connection or heater.

My first thought was that the thermostat was knackered, but I've just tested that with a pan of water and a thermometer, and everything is up to spec (starts to open at 88C, fully open at 100C, opens about 10mm).

Any suggestions? Air lock somewhere? Simply got too much water in, and it's venting the excess?

Where should the water level be when cold?

and finally,

What temperature should I see when it's ticking over on my drive?

cheers,

David

Symptoms indicate either a) knackered thermostat, or b) air lock.

As you have effectively eliminated the thermstat then it sounds like you have had an airlock around the thermostat area, so it hasnt been emersed in water, and subsequently hasnt opened.
When refilling, try loosening the top hose at the thermostat, to allow trapped air to escape. I guess that this is probably the highest point in the system now, except for your expansion tank......

when I had a 2 year old ford fiesta in 1978, whenever it was drained and refilled with water it always threw a wobbler and boiled over. Once it had done that and was topped back up, it was fine.

I put it down to an air lock.

Sometimes just squeezing the hozes with the cap off can help....


the expansion tank being the highest point is important I think - you dont have an issue with a 'high' section of piping trapping air?

The highest point is the Fiesta-style thermostat cover, which is ideal.

I think I'll try filling the block, then putting in the thermostat, fixing the cover and topping up the rest.

How high should the water level be?

cheers,

David

David, if the highest point is the thermostat, you'll need to make sure it is imersed in water to work properly, fill it up slowly making sure you squeeze the hoses to try to force out the airalso try (carefully) to run the engine without the stat cover on to make sure the stat lets water past it
Hope it helps
Jason

Forget testing the thermostat that way, it simply doesn't work properly. Gives duff results.

Could be an airlock, can you bleed at highest point of system? Cap on rad should be at highest point or a secondary filling point on an expansion bottle fed from top of rad is needed to vent air and get water level above engine.

Could be pump, they can snap impeller shaft and leave rest still turning. Rarish though.

Overfilling would spill out when hot but only after rad etc is up to temp.

Check cap poundage, I used a 15lb cap and an overflow bottle with bleedback.
I also had bleed screw in stat cap top.

I still believe it's the stat, with airlock maybe as well. Common on Xfows.

Testing 1 :-
Stats are cheap items, just cut off the bridge and remove the gubbins leaving just the plate. Fit the plate and refill. Test engine, it should now circulate and actually run cool.

Testing 2 :-
Go out and buy another stat and fit it.

I've had these things duff straight from box though.

Testing 3 :-
Check with cap off rad or whatever and check for circulation when revved slightly. This only works if stat is open.

Car should run at around 90 as a steady temp.


Rob Lane

Rob,

That gives me a few options to play with!!

A few answers to your comments/suggestions...

The thermostat, cap and pump are all new. As you say, that doesn't mean they're right, but lessens the chance of them being wrong.

When I tested the 'stat I used a thermometer from the laboratory where my son works... supposedly 0.5 degree accuracy... well, I got 103 degrees in a boiling saucepan! (and I did have the correct amount of thermometer in the liquid). This does put a question mark over my tests, but the error would be the 'stat opening early rather than late.

Test 1 is probably the next move - will probably do test 3 at the same time. Obviously, this will lead to test 2!



Many thanks,

David

Matter of interest - do I have to hack to pieces what may be a perfectly good thermostat?

Can I just leave it out - or does it form part of the water-tight seal around the cover?

cheers,

David

David, Just a quick cheat that is some simes used in the garage trade where vehicles are known to suffer air-lock problems around the thermostat. Take a small drill bit (1.0mm max) and drill a hole in the the thermostat plate to allow air to pass through. Some thermostat manufacturers build a small air bleed into the thermostat anyway.

Enjoy.

And thermostats control the flow of water around the cylinder block, no thermostat = hot spots in the cooling system

[Edited on 9/9/03 by jollygreengiant]

Thanks, JGG.

Another course of action to try...

David

I'm not suggesting leaving stat out but just for the test purposes. Cover will seal with a gasket without stat in.

I can't remember where I got my stat cover from but I had one with a small water pipe outlet which I drilled and plugged and used as a bleed. Can just be seen in pic below.

I'm sure it's air related and just needs bleeding out.
Rescued attachment CamCover.jpg

Wow, forgot how nice that Xflow looked with Webers on.

I've remembered now, it's a Fiesta stat housing with electric fan switch on top. The small pipe was removed and a thread cut in for a plug. You could also loosen the fan switch to let out air as a last resort.

I thought all thermostats had (or used to have) approx 2mm hole for air bleed with a 'jiggle pin' in it.

a jiggle pin was a small split pin to keep the hole from furring up.

atb

steve

ps - I recon 1mm hole might be too small and the water meniscus might not break through it.....

quote:

---

Originally posted by stephen_gusterson
I thought all thermostats had (or used to have) approx 2mm hole for air bleed with a 'jiggle pin' in it.

a jiggle pin was a small split pin to keep the hole from furring up.

atb

steve

ps - I recon 1mm hole might be too small and the water meniscus might not break through it.....

---

I've now drilled the hole (just over 1mm) and re-fitted everything, and it seems to have done the trick (although I haven't run the engine yet )

I got a remarkable amount of air through the hole when I topped up the system, and a whole lot more when I squeezed the hoses...

At the end, all I got were ripples in the water, so now I know that there's no air under the 'stat.

cheers to all,

David

David,

As you are aware, I've got a 1660 xf. On tickover (to answer your quenstion earlier on) the temp with fan on sits at 85 degrees. On a run it doesn't get any hotter (unless I forget to turn the fan on in traffic, or at the SVA centre).

Hope this helps.

Thanks to Rob and Mark

I now have a good idea what's normal - btween 85 & 90 degrees.

cheers,

David

Bottom hose went the other week and I replaced it. Got home and stopped the engine, it was like Mt Etna. I ran it while I filled it up after it had cooled and it's been alright since. If you run it with the rad cap off you can see when the stat opens and the level drops as the block fills to the top.

yours, Pete.

Pete,

In my case the stat probably wouldn't have opened - I think I probably had an inch or so of air under it. The temp gauge was in the water, but not the stat's wax capsule.

As I said earlier, I shifted a lot of air when filling after re-fitting the drilled stat!

cheers,

David