jabbahutt
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| posted on 2/5/07 at 03:45 PM |
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last coolant system question
Hi
been reading the threads on expansion bottles/tanks and need some confirmation.
I understand that a pressurised system the tank needs to go higher than the rest of the system on say the scuttle
An expansion bottle which is not pressurised doesn't and normally seems to be mounted near the front.
Hope that's correct. I can see how an expansion bottle system gets rid of the air as it's not a sealed system but how does the air
dissipate from a pressurised system as the expansion tank has a screw thread top on it?
If your rad doesn't have a pressure cap do you need to fit a non pressurised expansion bottle? or can you still have a pressurised system?
Also would I be correct than non pressurised has one pipe to the bottle and pressurised has two connections to tank?
Sorry for the ramble but the more I read the more confused I'm getting and a little clarification would be welcome in idiots terms.
Thanks
Nigel
[Edited on 2/5/07 by jabbahutt]
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tks
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| posted on 2/5/07 at 03:55 PM |
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No idea,
what i do now is that you only want one pressure cap!
and that a pressurised systems never gets air in or out (only when safety issues occur)
sow on my radi i ditched the radcap neck etc... and soldered on 2 nuts with to bolts to bleed air out.
on my expansion tank i have 2 entrances one higer as the other also the cap is there fitted.....
its easy really..
Tks
The above comments are always meant to be from the above persons perspective.
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dewbries
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| posted on 2/5/07 at 03:55 PM |
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hi there,
Might be talking out me bum, but i think if you have a rad with a non pressure release cap you will find that in its original fiiting it would have a
header tank with a release cap.
What rad are you using?
As far as i know all systems are pressurised, due to the fact that the heated water expands.
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jabbahutt
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| posted on 2/5/07 at 04:02 PM |
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I'm probably confusing myself and the fact that people use slightly different terminology just adds to me not understanding.
2.0 pinto engine with polo rad with no rad cap just two large connections and a small pipe at the top.
thing that confuses me is old systems rad had a pressuirsed cap which vented pressure but expansion tanks all seem to have a screw cap so I'm
wondering how the system vents air from the system
thanks for any help
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dewbries
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| posted on 2/5/07 at 04:11 PM |
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I am using polo rad. Have blocked off the small pipe, (that i believe is air bleed pipe which would have run up to the polo expansion tank).
The plastic screw on top on the expansion tank, mine is of a rover, are pressure release caps.
Yes older rads did have cap on top but that was when they were placed so that the top of the rad was higher than the engine.
Hope this helps.
Ps I have a zetec and when giving it some stick the rad is not really big enough, the temp soon rises.
Second build. Now refining and changing drive train
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BenB
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| posted on 2/5/07 at 04:42 PM |
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I know the plan about only having one pressure cap but my question is.....
WHY!
What difference does it make?
surely the one with the lower pressure rating blows first and the one with the higher rating never gets used..... I'd only see a problem if the
heater tank cap was rated higher than one elsewhere in the system...
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dewbries
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| posted on 2/5/07 at 04:46 PM |
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well that all sounds pretty logical to me.
Second build. Now refining and changing drive train
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dewbries
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| posted on 2/5/07 at 04:46 PM |
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well that all sounds pretty logical to me.
Second build. Now refining and changing drive train
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britishtrident
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| posted on 2/5/07 at 05:26 PM |
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A raddiator presure cap is actually a two way valve --- when the engine cools it allows air back in. Do you remember the classic crushed can
experiment in the school science lab ?
This why you should only have one presuure cap --- if you allow air in at two points you will get an air pocket forming that won't self clear.
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MkIndy7
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| posted on 2/5/07 at 06:06 PM |
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Also the Radiator pressure cap "blows off" at a lower pressure.
So instead of the water expanting off into the header tank bottle it just blows all over the floor!
"Ps I have a zetec and when giving it some stick the rad is not really big enough, the temp soon rises."
The Polo Rad is quoted by many of being capable of cooling 200+ BHP so maybe you need to be looking at why yours struggles.
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dewbries
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| posted on 2/5/07 at 06:11 PM |
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Am in the process of looking at why it struggles, but not all advise suggests it is that the polo rad is well capable. Was told upon purchase that it
should be ok for road but might struggle on the track.
I though zetecs struggles to get hot!!!
http://www.emeng.gentlyhosting.co.uk/Cooling/Part1.htm
[Edited on 3/5/07 by dewbries]
Second build. Now refining and changing drive train
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TangoMan
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| posted on 4/5/07 at 06:58 PM |
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quote:
Originally posted by dewbries
Am in the process of looking at why it struggles, but not all advise suggests it is that the polo rad is well capable. Was told upon purchase that it
should be ok for road but might struggle on the track.
I though zetecs struggles to get hot!!!
http://www.emeng.gentlyhosting.co.uk/Cooling/Part1.htm
[Edited on 3/5/07 by dewbries]
If you have blocked off the small breather pipe from the rad you may be getting air pockets at the top of your rad causing the overheating. Connect
the pipe from the rad to the header tank, possibly teed with the breather from the top of the thermostat housing. This will allow all air in the
system to reach the tank.
I would also check that your electric fan is pulling/pushing the right way.
Summer's here!!!!
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