7 replies to this topic

[Tornado99]

So my '88 carb Mini is still showing leakage from the petrol cap. Car had the sleeved type Monza flip cap when I got it and it leaked. This was a vented cap and there were no gaskets between sleeve and neck nor sleeve and screw-on flip cap. I changed this out to the standard non-vented locking cap. Seemed to seal better initially, but now I'm finding same staining down outside of body and fuel odour inside car if I fill it more than 3/4 full. 

 

I think the issue here is the filler neck is a bit distorted at the sealing surface. Plus, the "ramp" edge under/inside the sealing surface has worn. I can feel a "notch" in the ramp area right about where the either ear tangs on the locking cap would land...and this would mean much less sealing force from the spring-loaded cap seal (which is a brand new lucas type cap/seal by the way). 

 

Any suggestions on how to repair that neck sealing area? Should I go back to the monza flip cap and try to get the sleeve to seal better with some gaskets? 

Edited by Tornado99, 20 October 2021 - 12:43 AM.

[croc7]

I make cap gaskets out of 1/8” cork material, a little tight at first but they wear in after a bit. I replace them about once a year-better than the stock thin rubber ones.

[Miki Leyland]

I have the same problem of cap leaking when the car moves hard and have already bought the gasket from Minispares.

 

Should I glue it to the cap with any special petrol-proof stuff? 

 

I suppose it's a non-vented cap as the tank has a pipe from the top of the tank to the floor of the boot.

[Tornado99]

I have the same problem of cap leaking when the car moves hard and have already bought the gasket from Minispares.

Should I glue it to the cap with any special petrol-proof stuff?

I suppose it's a non-vented cap as the tank has a pipe from the top of the tank to the floor of the boot.

If you refer to standard type cap, not the flip type with neck sleeve, then the rubber seals are usually not stuck to the cap. Instead they are held along inner edge under a metal or plastic plate. I've not tried replacing one yet, so I assume they might just pull out from under that plate. Could be a pain to stuff fresh one under afterwards. Might be the plate can be removed in some way. Check for a threader nut or bolt or maybe a rivet that needs to be drilled out.
If going with an adhesive, stay away from RTV or silicone sealants as these will dissolve in gasoline. Epoxy will hold up but say a prayer from the next SOB that needs to remove the seal one day. I'd try a product like WellSeal or Locktite's gasket sealant which fuel resistant and does permit gasket separation in future.
A vented cap usually has a small visible hole somewhere on the inner plate. If tank has a vent line, be sure to plug the cap vent (epoxy is good here). Otherwise you may still get leaks out cap vent when tank is full.

[Miki Leyland]

 

I have the same problem of cap leaking when the car moves hard and have already bought the gasket from Minispares.

Should I glue it to the cap with any special petrol-proof stuff?

I suppose it's a non-vented cap as the tank has a pipe from the top of the tank to the floor of the boot.

If you refer to standard type cap, not the flip type with neck sleeve, then the rubber seals are usually not stuck to the cap. Instead they are held along inner edge under a metal or plastic plate. I've not tried replacing one yet, so I assume they might just pull out from under that plate. Could be a pain to stuff fresh one under afterwards. Might be the plate can be removed in some way. Check for a threader nut or bolt or maybe a rivet that needs to be drilled out.
If going with an adhesive, stay away from RTV or silicone sealants as these will dissolve in gasoline. Epoxy will hold up but say a prayer from the next SOB that needs to remove the seal one day. I'd try a product like WellSeal or Locktite's gasket sealant which fuel resistant and does permit gasket separation in future.
A vented cap usually has a small visible hole somewhere on the inner plate. If tank has a vent line, be sure to plug the cap vent (epoxy is good here). Otherwise you may still get leaks out cap vent when tank is full.

 

Thank you. I suppose it is the original of a 1973 car, with a key in the centre

[cal844]

They were all the same standard

[KevinS]

Hi,

I also had this issue and the final solution was the purchase of a replacement tank. At sometime after 1990, Rover manufactured a tank for cars fitted with a carburetor that had an anti syphon piece fitted in the neck. This also has the added benefit of stopping fuel leaks from the cap as petrol cannot now flow backwards up the neck. Not sure how lucky you'll be finding a replacement, it took me 5 years which involved a trip from Kent to Birmingham.

Before the replacement tank, I fitted a secondary black rubber sealing ring from an old cap which helped. No need to glue etc as I managed to slot it under the retaining lip. Best of luck. Kevin

[timmy850]

I bought a couple of “fake filler necks” the kind you stick on to make it look like you have twin tanks. They are the same dimensions as the stock neck, so I had one welded onto the damaged neck and it was much better