A310 carburetor question

[johnb]

I haven’t used the car (A310V6) for several months and recently noticed Type D coolant in the engine vee. So off with the carburetor/manifold assembly to investigate.



I had leakage into the vee previously and the culprit was where the small diameter hose from the back of the pump connects to the stainless curved pipe. The hose I originally installed there was a silicon hose from one of our usual sources but it was too large in bore size and didn’t tighten on the stainless pipe sufficiently. Fortunately I had a new Renault rubber hose, inherited with the car, which was tighter so this was fitted with the additional security of double jubilee clips at that end. That cured the leak at that time, as the new leak hadn’t then show up.

So now I’ve cleaned up the engine vee, plugged the ends of the open hoses and hung the expansion bottle from the garage rafters and left it overnight for a low pressure test. This showed a leak where the short, fat hose from the back of the pump connects to the block divider. Again, this was a new silicon hose and from memory wasn’t a tight fit on the divider. I’ll either try and find a tighter replacement but at least use double jubilee clips and then re-pressure test.

Whilst the carburetor/manifold assembly is off the car I thought it best to check for any leaks in this assembly. I connected the manifold coolant section to the garage tap, blanked the other side and applied mains pressure. No leaks found. This left only the small hoses at the single choke Solex 34TBIA carburetor, that feed the choke thermo element capsule housing and the butterfly heated housing. Again I used mains pressure to test. I appreciate that the mains pressure is significantly higher than the unit will be subjected to when operating but it did show a small leak between the thermo element and its housing. The pencil points to where the leak was in the next photo. This made me look at this assembly more closely and leads to my question (at last, you might say – just thought some background might be useful though ).



The thermo capsule arrangement is shown semi-diagrammatically in the Alpine manual, as below (item 1). The diagram in the Renault parts book shows an exploded view. In reality, the way mine is assembled is like my sketch below the diagrams from the manual and parts book. It is possible that mine may not be assembled correctly, just that this is the way it was when I bought the car. If you look at my sketch the only thing holding the capsule against the ‘O’ ring and against pressure from the cooling system is pressure from the spring (item 10 in manual diagram). The gasket (77 01 019 171 in the parts book) doesn’t appear to do any sealing. It just appears to be acting as a spacer.



Now to my question (at last ). When looking at the capsule on the web, I’ve found 3 kits, all with 2 ‘O’ rings and 2 aluminium washers as in the examples below. Does anyone know how these ‘O’ rings and washers should be assembled in relation to the capsule? Presumably one ‘O’ ring is assembled as on mine and possibly one washer on the brass hose connection to the housing (03 54 971 400 in the parts book diagram). The other hose connection is an integral part of the housing so doesn’t have a washer. The parts book diagram doesn’t show an ‘O’ ring at all.





As the Solex 34TBIA was used on a variety of cars and may, in itself, had variances; possibly both the ‘O’ rings and washers are not used in all applications. Does anyone know? Might seem to be a minor issue but I’d just like to know.
If anyone is looking for a new capsule this link might be useful.

http://www.ebay.fr/itm/Element-thermost ... FR_Auto_Pièces&hash=item43c0a0d603

Happy New Year to everyone.

No idea ....but I do have an A310 lump with the carb assembly sitting in the unit I can look at and see what's what .

[johnb]

Thanks Lee.
If you have a spare moment it would be interesting to know the arrangement on the one you have.
Thinking about it a bit more, I'm wondering whether the variety of 'O' rings and washers is to suit different versions of Solex carburetors that use the same thermo capsule. The list of carbs on the ebay link, in my post, might hint at possible variations of fit in the different carbs.

I appreciate that the mains pressure is significantly higher than the unit will be subjected to when operating but it did show a small leak between the thermo element and its housing. The pencil points to where the leak was in the next photo. This made me look at this assembly more closely and leads to my question (at last, you might say –



It is possible that mine may not be assembled correctly, just that this is the way it was when I bought the car. If you look at my sketch the only thing holding the capsule against the ‘O’ ring and against pressure from the cooling system is pressure from the spring (item 10 in manual diagram). The gasket (77 01 019 171 in the parts book) doesn’t appear to do any sealing. It just appears to be acting as a spacer.

First of all John, Nice sketch.
Trying to put a few things together from the above. I am sure that your sketch is the correct assembly, and it is quite possible that your mains pressure could overcome the spring tension. But under normal running conditions, if you look at that spring, it looks quite a strong one, which once the coolant starts getting hot, the spring will compress even further as the "actuator" comes out of the capsule, thus increasing the pressure to maintain the seal of the O ring.
If you remove the cap over the capsule, I think you will find that the final few mm's of thread when you tighten the two small bolts holding the cap, you will be pre loading the spring this making the seal. And you are correct, the paper gasket is just that, I can remember thinking the same when I removed the cap, although it is too thin to be a spacer, it could be because the faces it is between are not that finely machined.

Now to my question (at last ). When looking at the capsule on the web, I’ve found 3 kits, all with 2 ‘O’ rings and 2 aluminium washers as in the examples below. Does anyone know how these ‘O’ rings and washers should be assembled in relation to the capsule? ....................... As the Solex 34TBIA was used on a variety of cars and may, in itself, had variances; possibly both the ‘O’ rings and washers are not used in all applications. Does anyone know?

I am pretty sure you are right. These capsules shown are generic, and as such different carbs could well require the other bits, but when I took mine apart, if I remember rightly, there was only one O ring.
I had a look at what Simon Auto's were offering for this capsule and it appears that they offer an identical kit to the one you have shown, but twice the price.
But whilst we are on this subject, I would suggest that you slip off the small hose that is attached to the capsule cap ... not the one fitted to the brass outlet, but the alloy one. They can corrode very badly under the hose, but if you catch them early enough, they can be be repaired .... no one seems to have them any more, so a quick look could be a good idea before ... if it is badly corroded ... it breaks off. I suppose it might be 100%, but going on the condition of mine a few years back, I would be very surprised if it were.
I hope this helps. (now bleu's this out and copies )

John

[johnb]

First of all John, Nice sketch.

Thanks John, my background is mechanical engineering so I guess it has an influence. Thanks for your contribution also.

Trying to put a few things together from the above. I am sure that your sketch is the correct assembly, and it is quite possible that your mains pressure could overcome the spring tension. But under normal running conditions, if you look at that spring, it looks quite a strong one, which once the coolant starts getting hot, the spring will compress even further as the "actuator" comes out of the capsule, thus increasing the pressure to maintain the seal of the O ring.
If you remove the cap over the capsule, I think you will find that the final few mm's of thread when you tighten the two small bolts holding the cap, you will be pre loading the spring this making the seal. And you are correct, the paper gasket is just that, I can remember thinking the same when I removed the cap, although it is too thin to be a spacer, it could be because the faces it is between are not that finely machined.

You’re quite correct in all the above. I have a spare carburetor and earlier today did a small experiment to estimate the pressure exerted by the spring on the capsule. I like to have some real data, even if from a crude experiment, to eliminate unknowns and try and solve problems, if only for academic interest. As you say, the capsule is preloaded against spring compression by virtue of the gap between its housing mounting face and the face of the housing to which it attaches before the screws are tightened. So I put the carb in the vice, capsule pointing upwards with its cover over it but without the fixing screws in place. Then I needed a weight to lower onto the capsule cover so used a spare car battery (11.4 kg) and with this the gap just closed up completely, but not excessively easily. I was quite surprised that it needed this much weight to compress the spring.
As I had the carb/manifold assembly (9.8 kg) on the bench I repeated the test but this time the gap didn’t close completely. So from that the weight to take up the gap would be somewhere between the battery and carb/manifold weights. I then measured the capsule diameter at the ‘O’ ring and calculated the pressure at the ‘O’ ring interface due to the spring pressure. Surprisingly high, 105 psi with the battery and 90 psi with the carb/manifold. So, as a minimum, the spring force on the capsule would be producing a seating pressure of 90 psi with a cold engine and higher as it warms up. According to my manuals the coolant expansion bottle cap relief pressure is 12 psi, so far less than the spring seating pressure. This seems to demonstrate that the design of the capsule arrangement works. I feel a lot better now I know that!!
When I was testing with mains pressure, which, according to the pressure gauge near the boiler, is about 45 psi today; the leakage at the capsule was drops rather than a jet. Yesterday I put some Hylomar around the ‘O’ ring and today did a static test with the expansion bottle again in the garage rafters and no leaks found. Appreciate that this isn’t sufficient pressure but it didn’t show any sign of leakage here when on the car previously. It should be OK and simpler to get at if it ever leaks there in the future.

I am pretty sure you are right. These capsules shown are generic, and as such different carbs could well require the other bits, but when I took mine apart, if I remember rightly, there was only one O ring.

I do now think that this is the case. When Lee has a chance to look at the one in his workshop that might prove the point.

I had a look at what Simon Auto's were offering for this capsule and it appears that they offer an identical kit to the one you have shown, but twice the price.

Yes, I know. That’s why I included the Ebay link in case anyone was looking for one.

But whilst we are on this subject, I would suggest that you slip off the small hose that is attached to the capsule cap ... not the one fitted to the brass outlet, but the alloy one. They can corrode very badly under the hose, but if you catch them early enough, they can be be repaired .... no one seems to have them any more, so a quick look could be a good idea before ... if it is badly corroded ... it breaks off. I suppose it might be 100%, but going on the condition of mine a few years back, I would be very surprised if it were.

I was aware of this potential problem but mine is in very good condition, maybe because it wasn’t used by the previous owner for 20 something years. When I was restoring the car I totally stripped the carbs and refurbished them in the process. There was some corrosion at one of the coolant connections to the butterfly housing. It wasn’t too serious but I reinforced it externally with a coating of Araldite which seems to be holding up.

The large diameter hose that was leaking now has double jubilee clips and is on expansion bottle/rafters test until tomorrow, fingers crossed. I used up most of my stock of jubilee clips in the process due to them slipping at the crucial moment. Really need to find some ‘Rolls Royce’ hose clips as I’ve never found any that you can seriously tighten.

By the way, when doing this post I used the ‘Save draft’ button and when I came back to it clicked ‘post reply’ again and then ‘Load draft’ and it worked fine.

[johnb]

I had a look at what Simon Auto's were offering for this capsule and it appears that they offer an identical kit to the one you have shown, but twice the price.

Yes, I know. That’s why I included the Ebay link in case anyone was looking for one.

Here's an even lower price kit.
http://www.franzose.de/en/Renault/Alle/ ... /ANR72828/

They're showing 'Delivery time unknown' so presumably not in stock and may not be available.