Hi,
Is it normal for the coolant in the expansion tank to rise to near the top when it gets warm and then when the fan comes on, to go back to about 3/4 full very quickly.
Does this every time about every 5 minutes.
Does this sound like the system is working fine.
Used to have the fan on all the time and now it's on a thermo switch, didn't know the water expanded and cooled down so much and so quickly.
It's a sealed system by the way.
Pat...

Is it all back in one piece then fella?

Yep, up and running like Daley Thompson. Just got to finish tidying her up and then its up for sale and on with something to put the blade engine in that's sat quietly in the corner of my garage.
Pat...

Sounds like you might have some air trapped in the cooling system.

So could be a pocket of air expanding and contracting?
Squeezed all the hoses and no difference and the temp reads fine (sender on head). Idles at around 85-90 and gets to 100 before cooling down with the fan back to 85-90.
Pat...

Is the Rad Cap rated at the same pressure as the one fitted to the original engine. If its lower this could be allowing the expansion. I know it does usually expand but not sure how much it normally does.

Could be air traped some where like at the back of the block?

I don't know, that's why I posted!
How can I check?
I have a bleed screw on my polo rad and left it out until boiling water poored out and then pluged it.
Pat...

Presuming the top pipe for the water is at the front of the block, the front of the block needs to be raised, allowing air to float up and out of the block.

What do you mean be the top pipe?
Cheers,
Pat...

Mine is plumbed like this.
The small pipe from the top of the themostat to the top of the expansion tank is the highest bit of the system and I though this was to push any excess air out of the system and into the top of the expansion tank.
Maybe I should just jack the front of the car up a lot and let it run some.
Pat...

[Edited on 6/3/05 by Avoneer]
Rescued attachment plumbing.gif

quote:

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Originally posted by Avoneer
What do you mean be the top pipe?
Cheers,
Pat...

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No, it's a Pinto with polo rad.
The diagram shows three oultlets on the rad. It only has two, but the large bottom rad hose has a t in it and a smaller diameter pipe comes from this t to the bottom of the expansion tank.
Pat...

I get the feeling that this problem is outside my expertise.

My gues is given the plumbing set up there shouldn't be to much, if anything at all wrong with the system.

My one last quirey is that the thermostat is OK, though experiance says that a broken thermostate is more dramatic (then again that was on a simpler system with the thermostate at the top block not the bottom).

The stat is at the top, just looks odd in the pic.

Having thorughly confused my self and then realised/rememberd that the water pump draws in water from the rad, I can only say this.

Check all there is to check, if the termostate works, which at a gues it probably does, then the water level changes may just be a fact of the electric fan cooling system.

If the engine doesn't over heat, then live with it (keeping an eye on it), and unless someone else knows better then it probably isnt anything to worry about.

[Edited on 7/3/05 by clbarclay]

I've got a simpler expansion tank on my pinto using a Mk2 Escort radiator and it pushes about 1/2 pint of water into the tank when it's hot and draws it back when it cools. When I have air trapped in it it tends to push water out and generally make a mess. If it's not overheating I would put the bonnet back on and stop looking at it.

Thanks Pete.
That's the Locost answer I was looking for and I will now concentrate on something else (until steam envelopes the car).
Pat...

I dont see that you have a problem here. I have had a BMW before where if i filled the expansion tank slightly too full over the nexrt week the system blew the overfill out of the tank and it settled at its normal operating level. This indicates that some systems push water into the exp tank when required - this is of course why it is called an expansion tank. A mate of mine works on nothing else but LandRovers and has experienced the same several times. Not Pintos or Avons i know - but it shows that several vehicles share this phenomena.

If you are sure the temp gauge works ok and the fan cuts in correctly to control the temp then i would guess theres nothing to worry about. You might have just made one of those observations that most people dont see. i cant see where the air would be trapped in a Pinto. Do you have heated inlet manifold? This is higher or as high as the water jacket - maybe try cracking the joint there to see if there is air.

One small point - i was told to put the small pipe from the radiator cap 'bypass' (is this correct name??) to the bottom of the expansion tank. Reason - when hot water goes to the tank and level rises, when cooling the water gets pulled from the bottom of the tank and no air gets sucked back into system. It looks like your system might already do this by being piped differently. The problem we have is that there are so many rad / exp tank combinations that can work and all seem to have different connections. Im copying the Mac#1 method of plumbing when the time comes as i at least know it works for them.

you have plumbed your pipes in right.

It does sound like you have some air in the system still though, (not much mind you) jack the front of your car up as far as you can, (pintos need to be angled slightly in my experience) run the engine for about 5 mins with the expansion cap off.

This should hopefully cure it

Some pinto engines had a small pipe coming from thermostat housing, some had blanking caps on , If yours has one , with engine stopped take off cap and top up coolant level until all air is bled from pipe then refit cap. This should bleed all air from engine without any getting trapped behind thermostat. Some engines had this pipe connected to header tank I.I.R.C. also some expansion is norma lwhen engine gets hotter.