Swirl tank cap
Discussion
Like a lot of us I have had trouble with the traditional rad cap fitted on the swirl tank and fitted the extra rubber washer to improve the fit and so the sealing to help keep the water pressure at the specified 15lbs.
My S1 still had the undiginified habit of leaving its signature wherever parked and when I fitted a new cap without the extra washer it would would pea out the oveflow continually.
As I have now got a new rad, hoses, themostat and swirl tank as well as rad cap I thought all this was now over.
No chance, the washer mod to the cap was still needed.
To resolve this problem I took the old swirl tank(I never throw anything away-sad) down to our local car spares and asked for a good fitting cap.
I showed them the existing recommended QH/Halfords cap and they were sure that even with the extra washer the pressure achieved would only be a few pounds resulting in the system being prone to overheating.(I already knew that)
They soon produced a longer reach rad cap which fitted perfectly.
Problem it was only rated for 7 lbs and and for this type the highest rating was 10lbs and would hasve to be ordered.
But I was assured even the 7lbs rated cap would be higher than the existing bad fit and to try it.
I took the car out for a blast in 26C weather, no problem with temp guage at 90 . WhenI got back I let the car stand with the engine running and again no overheating so hot weather queing problems seemed sorted.
When I get the 10lb pressure it should be better still and when tested successfully I'll pass om the part no.
I will also try other makes for a full 15lb cap of this size(20m reach).
My S1 still had the undiginified habit of leaving its signature wherever parked and when I fitted a new cap without the extra washer it would would pea out the oveflow continually.
As I have now got a new rad, hoses, themostat and swirl tank as well as rad cap I thought all this was now over.
No chance, the washer mod to the cap was still needed.
To resolve this problem I took the old swirl tank(I never throw anything away-sad) down to our local car spares and asked for a good fitting cap.
I showed them the existing recommended QH/Halfords cap and they were sure that even with the extra washer the pressure achieved would only be a few pounds resulting in the system being prone to overheating.(I already knew that)
They soon produced a longer reach rad cap which fitted perfectly.
Problem it was only rated for 7 lbs and and for this type the highest rating was 10lbs and would hasve to be ordered.
But I was assured even the 7lbs rated cap would be higher than the existing bad fit and to try it.
I took the car out for a blast in 26C weather, no problem with temp guage at 90 . WhenI got back I let the car stand with the engine running and again no overheating so hot weather queing problems seemed sorted.
When I get the 10lb pressure it should be better still and when tested successfully I'll pass om the part no.
I will also try other makes for a full 15lb cap of this size(20m reach).
Bill
I have had exactly the same problem. It's as if the swirl tank throat dimensions are wrong? The design does not give anything like adequte compression of the spring within the pressure cap. I am currently using two thin home produced rubber washers to give a decent seal.
I have spent hours in professional motor trade outlets trying to find a 15lbs pressure cap of the right dimensions. If you review the manufacturers manuals, which quotes all the dimensions of the cap, you cannot find a match.
I have now resorted to ordering one from the factory through TMS, just to see what I get? So far it is still on back order!
I think that it is this problem that has given rise to people putting the pressure cap on the overflow tank and finding that the switch around works. The overflow tank does give the right amount of spring compression to the most commonly dimensioned rad caps (sold over the counter as replacements) and hence works.
I will keep you informed of any progress.
Hope to see you at an Eastern Region meeting very soon, sorry I have not been for a while.
ps. I am about to advertise my S3 and upgrading to ????
I have had exactly the same problem. It's as if the swirl tank throat dimensions are wrong? The design does not give anything like adequte compression of the spring within the pressure cap. I am currently using two thin home produced rubber washers to give a decent seal.
I have spent hours in professional motor trade outlets trying to find a 15lbs pressure cap of the right dimensions. If you review the manufacturers manuals, which quotes all the dimensions of the cap, you cannot find a match.
I have now resorted to ordering one from the factory through TMS, just to see what I get? So far it is still on back order!
I think that it is this problem that has given rise to people putting the pressure cap on the overflow tank and finding that the switch around works. The overflow tank does give the right amount of spring compression to the most commonly dimensioned rad caps (sold over the counter as replacements) and hence works.
I will keep you informed of any progress.
Hope to see you at an Eastern Region meeting very soon, sorry I have not been for a while.
ps. I am about to advertise my S3 and upgrading to ????
So far everything is OK with the 7lb cap and I have a 10lb one on the way which I may well end up with.
|Watch this space.
An upgrade, what will that be a Chim or a V8S or a Griff.
My best upgrade was Ridedrive lessons I just wasn't taking it as fast as it could go before.
See you at the next East Mids Meeting.
I let the side down ther this Sunday, having hitched a lift in Andrew Smiths nice S3.
There was an S2,S3,S4and V8S all at the meeting and I went left the S1 at home.
|Watch this space.
An upgrade, what will that be a Chim or a V8S or a Griff.
My best upgrade was Ridedrive lessons I just wasn't taking it as fast as it could go before.
See you at the next East Mids Meeting.
I let the side down ther this Sunday, having hitched a lift in Andrew Smiths nice S3.
There was an S2,S3,S4and V8S all at the meeting and I went left the S1 at home.
The 10lb pressure cap is now fitted and all is fine, no bubbling and gurguling or pushing water out through the overflow after stopping.
The Quinton Hazell part no is FC49.
Although QH only go up to 10 lbs with this cap I will try other manufacturers although 10lb seems OK and literally puts less pressure on the cooling system with no apparent loss in cooling efficiency.
The car warms up quickly and the heater gets good and hot.
The Quinton Hazell part no is FC49.
Although QH only go up to 10 lbs with this cap I will try other manufacturers although 10lb seems OK and literally puts less pressure on the cooling system with no apparent loss in cooling efficiency.
The car warms up quickly and the heater gets good and hot.
The Halfords 601 is made by Quinton Hazel no FC35.
It was one of these that I have just replaced because the reach is barely long enough and only works with an extra washer.
With the longer reach of the replacement there is no need and a good pressure seal is in place.
It runs OK at 10lbs with the temp at about 85.
Obviously if you are having no problems leave well alone.
It was one of these that I have just replaced because the reach is barely long enough and only works with an extra washer.
With the longer reach of the replacement there is no need and a good pressure seal is in place.
It runs OK at 10lbs with the temp at about 85.
Obviously if you are having no problems leave well alone.
Did have the car boil up once and thought it a problem with the fan not coming on quick enough so I'm now going to try the QH FC35. the car spat out steam and water at just over 90 with the Halfords one, but only the one time. any one know what temp the fan should switch on at?
gadgit.
gadgit.
gadgit said: any one know what temp the fan should switch on at?
90 degrees.
mine started gurgling after parking up about 4 - 5 months ago and i invested in a new cap from Halfords. A kind PH'er sent me some already prepared extra seals in the form of cut up bike inner tubes. No problems since then
Just to remind you about previous discussions about this.
Ihave used the long reach radiator cap(on the swirl tank of course) all this hot summer and have been stuck in sone long tailbacks with no problems.
I am slowly getting out of the habit of checking the water every trip to once a month but really there is now no need!
Bill
Ihave used the long reach radiator cap(on the swirl tank of course) all this hot summer and have been stuck in sone long tailbacks with no problems.
I am slowly getting out of the habit of checking the water every trip to once a month but really there is now no need!
Bill
There are two schools of thought about this.
If you put the pressure cap on the swirl tank, the overflow tank is redundant (unless the engine boils over, which should never happen unless something else is wrong). If you do this, the swirl tank should never be filled right up, you need to leave an air gap at the top. If you don't, it will probably blow water out. This way round works OK as long as you have a pressure cap that fits the swirk tank properly (standard pressure caps don't so they tend not to hold pressure). It has the advantage that it builds up pressure quicker (which is good). It has the disadvantage that there is relatively little air volume in the system which means it suffers more pressure variations - which is a bad thing.
The second approach relies on the pipe from the swirl tank going into the bottom of the catch tank. My V8S has this, so did my old S2, but I've seen others that don't. You are on a hiding to nothing if you use this approach with the wrong catch tank. Anyway, assuming the pipe *does* go into the bottom, you are far better off putting the blanking cap on the swirl tank and the pressure cap on the plastic catch tank. The swirl tank should be filled to the brim, and the catch tank should be empty when the engine is cold. When the engine is running, a small amount of water will be pushed out of the swirl tank and into the catch tank, and this will slosh back and forth between the two as you rev the engine and so on, but the catch tank should stay more or less empty. This first thing it does is act as a spring to reduce pressure changes through the system. The second thing it does is act as a settling tank for froth blown out of the swirl tank to settle out so only the water is drawn back. The catch tank takes a standard pressure cap. Obviously, this pressurises the pipe between the two tanks too, so be aware you might expose new leaks if you change the caps over, but the pipe is designed to hold the pressure.
Hope this makes sense,
Peter Humphries (and a green V8S)
If you put the pressure cap on the swirl tank, the overflow tank is redundant (unless the engine boils over, which should never happen unless something else is wrong). If you do this, the swirl tank should never be filled right up, you need to leave an air gap at the top. If you don't, it will probably blow water out. This way round works OK as long as you have a pressure cap that fits the swirk tank properly (standard pressure caps don't so they tend not to hold pressure). It has the advantage that it builds up pressure quicker (which is good). It has the disadvantage that there is relatively little air volume in the system which means it suffers more pressure variations - which is a bad thing.
The second approach relies on the pipe from the swirl tank going into the bottom of the catch tank. My V8S has this, so did my old S2, but I've seen others that don't. You are on a hiding to nothing if you use this approach with the wrong catch tank. Anyway, assuming the pipe *does* go into the bottom, you are far better off putting the blanking cap on the swirl tank and the pressure cap on the plastic catch tank. The swirl tank should be filled to the brim, and the catch tank should be empty when the engine is cold. When the engine is running, a small amount of water will be pushed out of the swirl tank and into the catch tank, and this will slosh back and forth between the two as you rev the engine and so on, but the catch tank should stay more or less empty. This first thing it does is act as a spring to reduce pressure changes through the system. The second thing it does is act as a settling tank for froth blown out of the swirl tank to settle out so only the water is drawn back. The catch tank takes a standard pressure cap. Obviously, this pressurises the pipe between the two tanks too, so be aware you might expose new leaks if you change the caps over, but the pipe is designed to hold the pressure.
Hope this makes sense,
Peter Humphries (and a green V8S)
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