Webers Leaking

[LoTex]

I've recently noticed (and smelled!) a slight leak from the back Weber carb on my 65 S2 Elan. When I take the breather box off the last venturi has a thin sheen of dark brown liquid covering it, which in places has leaked through the breather box onto the ledge of the engine compartment and coats the underside of the breather box. I say liquid because although given where the leak is I'm sure it is gasoline (petrol) it is much more viscous and darker in color (looks more like molasses or treacle) and does not have a typical gasoline odor.

Has anyone encountered this before, and/or have any ideas on what the problem is and how to fix it?

Cheers

Steve

[ardee_selby]

Oil mist? Breather tube fitted? Does this thread chime with what you're experiencing?

elan-plus-f13/advice-carbs-airbox-clogged-with-oil-t13434.html

[LoTex]

Richard,

A number of good suggestions here, will try to check them out this weekend. Thanks for your help!


Steve

[rgh0]

It could be oi lfrom the breather as discussed or could be fuel. Petrol can leak from between the venturi inserts and the carb body on webers if the spring clip that holds the venturi in place has lost its tension. Even with good tension in the spring leaks can occur. The fuel runs back into the airbox between the venturi and carb body where it evaporates leaving a reddish brown residue of heavy fuel components.

Fitting a gasket to seal the venturi to the carb body has been discussed here previously

cheers
Rohan

[LoTex]

Thanks!

I think I have sorted the original problem out by making sure all the clips that secure the venturis are in place and tight. However when running then revving the engine to make sure no leaks are occurring there was on revving the engine a slight mist of petrol coming from the back venturi on the front carb. That seems dangerous. Any ideas what's causing it?


Steve

[rgh0]

I presume what you are seeing is fuel mist coming out of the mouth of the carb inlet trumpet at certain revs. This is normal and is caused by the pressure waves in the inlet tract that you get this. Normally it is contained within the airbox and not a problem and the fuel stays suspended in the air and vaporises and is sucked into the engine.

This is why you always need to run with some sort of airbox or other arrangements on the carbs to contain this fuel cloud otherwise you can get ignition of the fuel cloud !!!!

If it is still leakage between the venturi and carb body then you may still not have got the No4 venturi tight enough in its body or you need to make some sort of seal arrangement between the ventrui and the body.

cheers
Rohan

[ardee_selby]

Steve,

This video (http://www.youtube.com/watch?v=RSSYcVTUrT8) was referred to in a thread about fuel "stand-off".

Interesting to see it in action here (at about 1m20s) but all 4 are acting in the same way.

So, as Rohan has said, only one would suggest that it isn't sealed as effectively as the others.

[LoTex]

Rohan, Richard-

That video was pretty impressive.

Thanks for all the help, guys!! I'll double check that venturi and then put the air box back on, hopefully won't see any more leakage.


Steve

[Allison]

Steve or possibly Rohan,

Your answers go some way to explain the mess we have in the airbox at No4 where there is a oily/watery goo which involves the base of the airbox and the breather tube. The fuel leak we have is from the blanking plate at the rear of nos 1/2. I've replaced the paper seal but I suspect its the (?) accelerator pump which is leaking fuel into the chamber. Any ideas on how to rectify that?

Many thanks
Peter

[ardee_selby]

Steve or possibly Rohan,

Your answers go some way to explain the mess we have in the airbox at No4 where there is a oily/watery goo...Many thanks Peter

"Oily/watery goo" as opposed to fuel residue?

Apart from the fuel leakage you've identified, any sign of the same "soup" under the filler cap?

[Allison]

Richard,

no the engine was rebuilt recently and the goo was there before and after and only in the region of that breather tube
Peter

[rgh0]

The grey goo is a water oil emulsion coming out as a vapor or fine mist from the breather tube and condensing in the airbox. A small amount may forn in norml use with a good engine

Causes for excessive amounts are typically to much blowby gas putting water in the oil , engine running at too low temperature due to short runs or low thermostat temp leading to build up of water in the oil or a water leak into the sump or some combination of the above.

Do you run a synthetic oil as these seem to form the emulsion more strongly in the presence of water.

The formation is also accelerated by the presence of reactive olefinic compounds in the unburnt gasoline in the blow by gases

Learnt all about this whe I was running a ethylene plant that supplied a lot of gasoline as a byproduct to the local refinery and when new mercedes and bmw had sludge problems in their oil they tried to blame us for olefins in the gasoline we supplied

Try draining the oil and see if any water or anti freeze or a grey sludge comes out when you first pull the drain plug after leaving the engine sit for a few hours

cheers
Rohan

[LoTex]

Thanks to suggestions from Richard and Rohan I believe I have solved the leak issue, having cleaned and re-secured all the clips on the venturis. The air box is back on and although I couldn't take her out for a drive today I ran the engine for quite some time without any fluids observed below the air box. The real test will be a good run on the road, will do that next weekend.



Steve

[512BB]

Peter[Allison] wrote: The fuel leak we have is from the blanking plate at the rear of nos 1/2. I've replaced the paper seal but I suspect its the (?) accelerator pump which is leaking fuel into the chamber. Any ideas on how to rectify that?

Years ago I had the very same problem on my Elan. I charged a specialist firm with curing the problem, and they charged me nearly 300 quid for the priveledge, stripping both carbs and re assembling.

Drove home happy as a Larry. THEN INSPECTED! Fuel still dripping down onto the dissy! Phoned up said company, who told me they had spent much time on rectifying the fault, and they were not going to have another look, unless I paid more money for them to do so.

Oh really I thought, notice given, and then papers served. Result.......LMS 1 Co 0. Money refunded in full, plus my costs. Silly boys, as my old French teacher used to say, Mr Galleb [Harrow].

However, problem still with car. Finally sorted when I ...............................bought new carbs!

So, as Peter says, what causes that problem and how does one cure? Purely academic in my case, but curious.

LMS

Sorry for hijack