GT6 Boiled Over...

[Iain T]

49 minutes ago, Kevin Atkins said:

I think my mate was a bit unsettled by the symphony of rattles, squeaks and general racket my GT6 makes.

Better to use a car than have a show piece where you're frightened to see the light of day! 

Only my Vitesse and a Spitfire at Brands plus a TR2 racing. 

Then there's this trio of historically important race cars, a Lister, Connaught and Frazer Nash. Yes I did dribble..... 

 

[SpitFire6]

On 14/07/2023 at 17:26, Ian Foster said:

Didn't know that. I suppose this is an option, but it might be better to use a 7lb cap on a 13lb system, as the additional compression would increase the effective spring rate.

Ian

Hi Ian,
That's interesting what you say.
I have always thought that if the cap fits & it requires force to fit, it will open at the stated pressure. If it fits, the spring is never coil-bound and will therefore move if pressure is reached.
I have always assumed the spring rate on a rad cap is linear & therefore its rate is not affected by the load that is put on the spring.
Cheers,

Iain.

 

[Iain T]

11 minutes ago, SpitFire6 said:

I have always assumed the spring rate on a rad cap is linear & therefore its rate is not affected by the load that is put on the spring.

The design of the spring does indicate linear compression. I can't see any variation in pitch or conical shape. Therefore as long as the lower seal has slight compression to the rad it should release at 13 or 7lbs.

Iain 

Edited July 17, 2023 by Iain T

[johny]

Just to clarify, all springs have a rate and a linear one means than for each mm of compression the force exerted goes up by a regular set amount. For example a 1lb per mm spring if compressed 5mm will exert 5lb of force so the more the rad cap spring gets compressed during installation the greater the cooling system pressure needed to open it..... 

[Pete Lewis]

one thing not mentioned is the seal rubber often grows with nasty rubber /contamination and the seal fully fits the diameter of the filler neck 

so it restricts the escape of coolant if the seal lifts off its seat

Pete

[Ian Foster]

4 hours ago, johny said:

the more the rad cap spring gets compressed during installation the greater the cooling system pressure needed to open it..... 

That is my understanding also. So a 1" deep cap fitted into a nominal 3/4" deep radiator neck, would be opening at a higher pressure than intended.

Ian

[Iain T]

Yes it will, I didn't explain myself well last night. The compression force against distance graph is linear but not horizontal so force will increase with distance compressed. Dimensional variations in neck and cap will result in varying forces to release rad pressure. Now we know one reason all modern caps are screw on? 

Iain 

[Gully]

On 16/07/2023 at 17:20, daverclasper said:

Do you know who supplied it please gully. Same issue on mine (though Vitesse). Currently using a rubber washer and about a 5mm thick washer to reduce the depth.

Maybe not sealing where it should, as have empty section/sections of overflow hose always.

No problems with overheating, even when really hot ambient temp and traffic jams, so not the end of the world I guess?

Thanks, Dave

Mine came from Car Builder Solutions: https://www.carbuilder.com/uk/radiator-caps

Gully

[daverclasper]

5 hours ago, Gully said:

Mine came from Car Builder Solutions: https://www.carbuilder.com/uk/radiator-caps

Thanks Gully

[Kevin Atkins]

It's great to read all the replies, sharing all the knowledge and experience - owning this car and meeting everyone (if virtually) has been great!

Been for a good long run today, and I think the cooling system is now behaving itself - there's a rise of maybe a couple of inches in the expansion bottle when hot, and coolant is returned to the radiator on cooling, and temperature gauge is steady, rising very slightly when trickling along in town traffic.

The little car is now running well, so thanks to everyone here - I'm trying to get some miles under the wheels so I can get the head retorqued as soon as possible and then I think it'll be a wrap on this hopefully!

[gt6j]

On 03/07/2023 at 15:02, Kevin Atkins said:

have been through two top hoses, which have both split along the seam.

Hi Kevin not sure if it helps but had similar with three top hoses splitting on my mk3. Bought a silicon reinforced length of the same diameter off ebay and cut to length had no leaks there since. 

[Kevin Atkins]

On 26/07/2023 at 23:50, gt6j said:

Hi Kevin not sure if it helps but had similar with three top hoses splitting on my mk3. Bought a silicon reinforced length of the same diameter off ebay and cut to length had no leaks there since. 

Thanks for the tip - I will at some point go down the silicon route I think but for now, the car is running well and I can't stomach doing another cooling system drain etc! I did buy a reinforced top hose off eBay and it seems better made than the others I've tried so for now it'll do.. The ballooning hose issue I had turned out to be a useful indicator that there was trouble in the system though, traced to the radiator neck / cap, so in a roundabout way it was a good thing I guess 😜