Amazon: Weepy Stromberg advice.

[Alf ista]

Hi all. Haven't posted in quite a while, though I do check in most days. I have an issue with my Stromberg carb and I hope the knowledgeable folk on here will give me some sage advice. As you can see in the pics below there is a leak from the carb that is going onto the manifold. Obviously not the best situation, though I do feel it is just the dashpot oil as I need to top it up with oil before every spin. I use ATF. I want to fix this but am not sure what is causing the problem. Is there a particular seal inside the Stromberg that normally causes this that needs replacing or could it be something else? Any advice appreciated.
Hugh.

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[Triple-S]

Strombergs have a habit of leaking petrol from the O-ring seal at the bottom of the float chamber - does your leakage smell of fuel? Admit it looks like oil from the pic, and seems to be coming from the carb-to-manifold join.
Could you be over-filling the ATF in the dashpot? You have to leave enough space for the screw-in plunger otherwise it will force excess out. Does your car smoke a bit when first started - as if oil is getting into the manifold then engine?
If you do need to check that bottom O-ring it is frankly easier if the carb is removed from the car (4 nuts) as it probably means removing the float chamber from the bottom. The seal is at the bottom, to prevent the contents from leaking (not a good design), however some models of cars have a decent-fitting plug there - still, a look will give the opportunity to clean it out of the almost-certain crud the fuel filter hasn't caught.

P

[Ron Kwas]

Hugh;

I have very little experience with ZS so the following advice will be general only...fuel would evaporate quite quickly for the hot manifold after motor shut-off, ATF less quickly, and needing to top it up often pretty much confirms that is what is weeping/leaking...so its a matter of finding the path ATF is taking...I agree with OP...removing carb from manifold and giving it a careful once over (with a particular eye on any path or seals or seams between ATF holding compartment and intake tract) would be my next move...

Good Hunting!

[Derek UK]

As said, don't over fill. Fill tube only to about half an inch from the top. The piston will displace a bit and raise the level anyway. I'd use 3 in 1 or 20 sae. The small, cheap, general purpose light oil cans from the supermarket are fine and they usually have a convenient nozzle. Not much difference in viscosity to ATF but a bit more sticky and less prone to flow. Might be a good time to pop off the top and fit a new diaphragm after a good clean up.
Yes the lower O ring seal can weep on the carbs with the removable bottom nut but that doesn't look to be the case here.

[Alf ista]

Thanks all. There is no smell of fuel so I am sure its not that. I have replaced the diaphragm in the past so I think that is ok. I also don't overfill the dashpot, I think anyway. Could the oil leak from the carb to manifold gasket if that had failed? To me, it looks like it comes from there and it would be an easy fix if that was the case.

[volvoid]

arent y supposed to put engine oil into a dashpot ?

[Volvorama]

Throw it away and get an SU HIF 44 with manual choke. Vastly better unit.

[Pigeon]

Originally Posted by Alf ista

I also don't overfill the dashpot, I think anyway.

I think you do, because this is what happens: the excess oil comes out the top and runs down onto the top of the manifold flange and then onto the top of the manifold, where you notice it because it makes the surface change colour, and eventually down over the rest of it. And this...

Originally Posted by Alf ista

...the dashpot oil as I need to top it up with oil before every spin. I use ATF.

...is how you can tell you're probably putting too much / too runny oil in.

I reckon your first move ought to be to top it up with engine oil to your usual level, take it down the road and back, have a look to see what level it's gone down to, and then recalibrate your notion of "full" to correspond with that level.

Originally Posted by volvoid

arent y supposed to put engine oil into a dashpot ?

There are as many "supposeds" as there are owners but engine oil is what I've always used. I've tried various lighter oils for experiment at times, and found they never make any noticeable difference to the throttle response. As far as correct carburation is concerned, it seems that as long as you do have some sort of oil in there that's the important thing and it doesn't much matter exactly what sort it is. Lighter oils, however, are significantly more prone to being thrown out the top.

Originally Posted by Volvorama

Throw it away and get an SU HIF 44 with manual choke. Vastly better unit.

Me, I'd go for an HS6, but neither swap will make any difference if it is user error.

[dingov70]

You have excess oil in damper tube & that has been forced out of black cap vent hole . Fuel would not leave such a " damp" looking patch on the manifold & you would definately smell it and notice running issues

[Alf ista]

Thanks for the feedback. The reason I use ATF is because that was the general consensus for a Stromberg on this forum when I first got the car. I wonder do SU's need a different weight oil? Nevertheless I might try engine oil or 3 in 1 and see how that goes. I am filling it to about a 1/2 inch like I always have done and it didn't leak like that before, after so many years of ownership I didn't just start overfilling it. I had another look and the top of the carburetor is bone dry with no sign of oil. It does appear to be leaking down further around where the carb joins the manifold. I can take it off, clean it up and replace the gaskets but does the dashpot oil flow around that area? It doesn't like it does to me on the diagrams.
I often read about Strombergs getting bad press, but honestly in all my years with this car it has been perfectly reliable. When I changed the exhaust and air filter the old B20A pulls like a train, even with its Stranglberg... Someday I may change them out for twin SU's and a camshaft change but that is a good bit down the road.