How long should carb diaphragms last????

[marshman]

MoT'd the car yesterday morning first thing then decided to carry on to work - first real run this year (I know but life is far too hectic at the moment!) - anyway gave it plenty of right foot to blow the cobwebs away and it ran sweet as a nut. On the way back - mid afternoon had a run into town - hot and lots of traffic but no dramas - got onto the open road and barrelled along overtaking anything that was in danger of getting sucked into the air intake and noticed a couple of hesitations as I put my foot down, the further I went the more "off colour" the engine was. A couple of miles from home I felt we were limping along so I nursed it home and put it into my garage. Tick over was really lumpy and I had to pull the choke out a bit to stop it stalling.

Anyway I kind of ruled out ignition as the symptoms were too consistent and I went through that loop 2 years ago. I disconnected the throttle linkage to the LH carb so I could operate each carb throttle independently. RH side was fine. LH side was "slugglish" to the point I could open it fully without the engine revving freely. So decided to lift of the top of the carb and found the diaphragm was split. I only replaced these 2 years ago. Whilst I was about it I checked the RH one which was nearly as bad. I fitted a new pair and the engine is once again "on song" but as they are of the same vintage I have no confidence that they will last any longer.

The question is what is a reasonable life span for a diaphragm?? They were both purchased from one of the usual suppliers and to my knowledge I havn't filled the car with any high ethanol fuel (yet!)

Roger

[martin]

Hiya Roger, quality is so variable, they can last anywhere from 20 minutes to about five years, two years is not very good, but not a disaster, also there's no way to tell how long they've been in stock. The best, are the earlier thin rubber ones. Martin.

[redstag]

I fitted brand new carbs when I restored my car and nearly 12 years and 50,000+ miles later the diaphragms are still fine.
I checked them last week and no signs at all of perishing or splitting. I remember being worried that the original diaphragms wouldn't last with that unleaded stuff!

I always carry a spare pair though, they will undoubtedly fail at some point.

Pete

[redstag]

Hiya Roger, quality is so variable, they can last anywhere from 20 minutes to about five years, two years is not very good, but not a disaster, also there's no way to tell how long they've been in stock. The best, are the earlier thin rubber ones. Martin.

Interesting you should say that Martin as the ones in my car are very thin and flexible, much more so than the spares I have.


Pete

[marshman]

Hiya Roger, quality is so variable, they can last anywhere from 20 minutes to about five years, two years is not very good, but not a disaster, also there's no way to tell how long they've been in stock. The best, are the earlier thin rubber ones. Martin.

Thanks Martin but the problem is this is only Stromberg carb I have dealt with so can't really gauge thick or thin - they seem thin and floppy to me. ( I prefer older diesels - change the engine oil regularly and a new air and fuel filter occasionally and your good for a few hundred thousand miles!). Would I be better off going to somewhere like Burlen and buying some from them - would it guarantee the quality?

Roger

[ChasR]

To play it safe I would order genuine SU bits on the Strombergs (Burlen do these). Aftermarket rubber in the classic world is so variable it seems with many suppliers.

[martin]

Thanks Martin but the problem is this is only Stromberg carb I have dealt with so can't really gauge thick or thin - they seem thin and floppy to me. ( I prefer older diesels - change the engine oil regularly and a new air and fuel filter occasionally and your good for a few hundred thousand miles!). Would I be better off going to somewhere like Burlen and buying some from them - would it guarantee the quality?

Roger

Hi Roger, the later ones (Nitril I think) can be pretty robust, but the rubber ones suit the environment and seem to last better, mine have been in for eight years, (55.000 miles) I would think buying from Burlen is your best option. Some folk supply both, the thin ones being dearer, don't know why. Not a critical issue, but bloody annoying when they go. At least they're an easy cheap fix Martin.

[Staggard]

Hi Roger, the later ones (Nitril I think) can be pretty robust, but the rubber ones suit the environment and seem to last better, mine have been in for eight years, (55.000 miles) I would think buying from Burlen is your best option. Some folk supply both, the thin ones being dearer, don't know why. Not a critical issue, but bloody annoying when they go. At least they're an easy cheap fix Martin.

This add's fuel to my fire about having a seperate page on the forum where members can list good quality parts and who supplied them.Graham

[martin]

This add's fuel to my fire about having a seperate page on the forum where members can list good quality parts and who supplied them.Graham

One problem with that Graham, I've bought good ones from poor suppliers, and poor ones from good. I don't envy the position you're in, if I buy something faulty I can pop it back and swap, bit different in the Canaries. Martin.

[V Mad]

When I was doing rebuilds of Strommies I found that the new diaphragms were so stiff they would prevent the piston dropping quickly and making that nice clunk sound. Instead they would hover and eventually drop, sometimes the left/right at different speeds. And those were from one of our favourite suppliers. I dont think you can get original quality any more, unless someone knows different?

[martin]

Try here http://www.jamespaddock.co.uk/parts....text=diaphragm Martin.

[Stagdad]

I bought a genuine zenith rebuild kit and also found the rubbers to be so stiff I left the originals in which were the thin type and still good.

Cheers Steve

[Klaus Schlueter]

[/QUOTE]. I dont think you can get original quality any more, unless someone knows different?[/QUOTE]

I have just bought one from Mercedes in Munich. Part no. 000 071 08 26. Price appr. €12.- incl. tax. No delivery time, still in the shelf.

Klaus