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Hi all I recently bought a new rad cap for the 4A, Moss part no GRC112SS which has the lower siphon valve for coolant recovery systems, however this cap no longer comes with a rubber top seal under the cap a relies on the spring steel disc to make the seal.  PHOTO 1.                                                              A friend also bought a cap for his TR6  at Stratford upon Avon Interclub and it didn't have a top seal either.

Question is will the cap with just the spring top seal and no rubber top seal be airtight for the coolant recovery system ( I doubt it). I have at the moment transferred the seal from my old cap but would have preferred a new one, can't find replacement seal only anywhere.

Photo 2, found on internet shows original style cap with rubber top seal on right, but this Cap does not have the spring disc like the newer caps so it obviously needs the rubber seal.

radcap1.jpg

radcap11.jpg

Edited by ChrisR-4A

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My similar new Moss cap for the TR6, which also has 2 seals, came with both seals. The upper (larger) seal however is made of very soft rubber sheet, this will help sealing (maintaining) the vacuum but I doubt it will last long. You can fabricate your own easily, it is made from rubber sheet, so I did not contact Moss.

Regards,

Waldi

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Thanks Waldi, I've since found a photo on Moss web site which clearly shows a seal on the cap part no I bought so have contacted Moss to request a seal.

Chris

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My new cap from Moss (12 months ago? not sure) had the top seal but it's loose. I have to check it's in position and that it doesn't get pinched every time I replace the cap - which is a (minor) pain. I wonder if yours just fell out between the factory and you receiving it Chris?

Cheers, Richard

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You definatly need a soft seal between the rad top flange, & the rad cap body.  no good just adding a seal to the sprung metal part.

I modified a TR3 cap (deeper lower seal) to have a top seal, but had to grind out the springy disc first.

I can top my rad up to the brim, & the level stays there as with perfect sealing all the expanded coolant gets sucked back in when engine cools .

Bob.

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57 minutes ago, Spit_2.5PI said:

My new cap from Moss (12 months ago? not sure) had the top seal but it's loose. I have to check it's in position and that it doesn't get pinched every time I replace the cap - which is a (minor) pain. I wonder if yours just fell out between the factory and you receiving it Chris?

Cheers, Richard

Same with mine Richard. But it works ok (the overflow bottle is emptied when the engine cools down.

Waldi

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Hi Chris,

I would take a closer look about the distance from your DIY seal down to the seal of the spring loaded valve.

Is there still a load on this valve when you lock the rad cap? Don't choose your seal too solid.

Ciao, Marco

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2 hours ago, Lebro said:

You definatly need a soft seal between the rad top flange, & the rad cap body.  no good just adding a seal to the sprung metal part.

I modified a TR3 cap (deeper lower seal) to have a top seal, but had to grind out the springy disc first.

I can top my rad up to the brim, & the level stays there as with perfect sealing all the expanded coolant gets sucked back in when engine cools .

Bob.

Bob, the springy disc appears on all the caps now and is made integral with the cap so when a neoprene washer is added then the cap seals as per the original design. Same cap is sold by all suppliers either with or without the seal depending on intended application.

The flexing of the disc behind the washer may even improve the seal.

Chris

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That’s about 13psi isn’t it ?

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Yes it is Hamish.

Waldi

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1 hour ago, ctc77965o said:

Dave I ordered two of these and they were too small to go on the rad neck. Yours obviously fits and is the correct size. I just threw mine away and must of come from a different manufacturer in China.

Regards Harry TR5 Nutter

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Tangent.....Expansion tank.

Does this look cheap to you?

https://www.ebay.co.uk/itm/1L-Coolant-Water-Expansion-Tank-Bottle-Header-Aluminium-Alloy-Universal-Kit-Car/123857908659?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D61046%26meid%3Dd9a30011a16e4cacb97769cb78ec01d5%26pid%3D100005%26rk%3D1%26rkt%3D12%26mehot%3Dpp%26sd%3D174067653474%26itm%3D123857908659%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851

 

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Peter & Bob = nice looking can.  I noticed the lack of pressure cap, then found this in the description:

Please note - an inline pressure cap should be installed along with this tank.

This means that one would need to put a T-piece in the line, and devise a mounting for a pressure cap - easier to use a secondhand can, such as that from a Triumph Dolomite.  Then one trasfers the pressure cap from the radiator to the can, and buys a sealing cap (no internal pressure seal) for the radiator..

Incidentally, 0.9 bar (near 13 psi) on Dave's cap with temperature gauge is too high for a TR.

Ian Cornish

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UPDATE: 

I messaged Moss and they replied promptly that as assumed the cap should have had a top seal  but some of their stock had them missing.

They  are sending a complete new cap with seal FOC, Excellent service. The  morale of this saga being, If in any doubt about an item then ask the Forum and do contact the supplier not only for your own benefit but to avoid others having the same problem.

Excellent service from Moss

Chris

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IMG_20191126_095739-1587x1190.thumb.jpg.d439689a90cd1c7f0acf066464dc2d83.jpg

There's two sizes, a small one for ricerockets and this larger style for proper radiators. Yes 0.9 bar is higher than spec, but it works fine for me.

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My TR4A already had a 13 PSI rad cap when I bought it 10 years ago,

this still works well without any problem.

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Most radiators in good condition should be able to withstand 13psi but this is nearly double the pressure Triumph designed the car to run at. Bearing that in mind I would question whether a 50+ year old heater matrix would be ok, also some of the hoses in particular the two heater hoses inside the car near the drivers left leg (RH drive cars) need to be in good condition and not too old. It's not only car tyres which degrade with age.

A few years ago one of our members suffered second degree burns when one of those hoses blew off and covered his legs in boiling water, I was in convoy  with him at the time and his legs were not a pretty sight,  which prompted him and myself to fit a small alloy cover round the hoses to contain and deflect the water in case it happens again. This was at 7 psi, at 13psi  more than double the amount of water would escape and in the footwell there is nowhere to move your legs out the way you are trapped!

Chris

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On 11/25/2019 at 8:44 AM, ianc said:

Peter & Bob = nice looking can.  I noticed the lack of pressure cap, then found this in the description:

Please note - an inline pressure cap should be installed along with this tank.

This means that one would need to put a T-piece in the line, and devise a mounting for a pressure cap - easier to use a secondhand can, such as that from a Triumph Dolomite.  Then one trasfers the pressure cap from the radiator to the can, and buys a sealing cap (no internal pressure seal) for the radiator..

Incidentally, 0.9 bar (near 13 psi) on Dave's cap with temperature gauge is too high for a TR.

Ian Cornish

Dolomite tank from eBay £23.

 PhotoPictureResizer_191127_155042284_crop_932x1014-233x253.png.9be31d2353ef09994ad19a30c97f315f.png

A foot pump with gauge can be used to Chech it holds pressure, about 20 psi will do and this will also pop out any small dents.

Fitted after a clean up and paint.

 

IMG_7956.jpg

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Oh dear, Chris - you have put me to shame!  I had better dismantle my rather tatty Dolomite header tank and give it a lick of paint!

Neat mounting arrangement, but my car has a couple of coils and pair of Italian air horns over there - very crowded!

Ian Cornish

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I did have an expert to guide me Ian, I looked closely at the photo of  Stuart's car. Thanks Stuart.

PhotoPictureResizer_191128_163348479_crop_164x165-82x83.png.907c39db5763cfa006a60b41c5513175.png       Chris

Edited by ChrisR-4A

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