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MG Midget and Sprite Technical - Keep away from Silicon and RTV

I have just got my Type 9 back from JC Transmissions in Paisley. The owner has been rebuilding Type 9s for 50 years and he worked on my box personally. When stripped it was in excellent condition but he did modify the second synchro hub and replaced some springs. He charged me £150. On the bench all gears slipped beautifully into engagement until I replaced the new Ford to MG bell housing, then stiffness and notchiness occured. I immediately feared a poorly machined unit but when I had assembled the box first time around I didn't have the gasket that fits between the bell housing and main case so used some RTV sealant instead. Some of this had squeezed into the blind hole the selector rod moves into. This was fouling entry of the rod and after cleaning out, selection was again perfect. I know the advice is never use Silicon or instant gasket on an engine for fear of blocking an oil gallery. I thought it would be OK for a gear box but I was a fool. It's Wellseal and a gasket in future.

Jan T
J Targosz

Personally I like Blue Hylomar. I've used it for decades and have yet to have an issue with it.
Greybeard

Yep I agree. Silicon sealant is grotty stuff in the wrong places. I don't use either, I always use hylomar too.

Hopefully that's sorted then. He must mean 50 years building gearboxes Jan. The type 9 is only 40/1 years old. First to have it were the Capri and Sierra in 1982/3.
anamnesis

Hi Anam,

The reconditioner said he served his apprenticeship working on Ford 2000E gearboxes which were the forerunner of the Type 9. He believes these to be one of the best boxes ever made and Ford spoilt them when converting to a 5 Speed. It was the 2000E box that earned the reputation for the slick shift.

Jan
J Targosz

I reckon some other makers of gearboxes might argue with that claim Jan. Not that I know personally though.
anamnesis

Nothing wrong with silicone sealants, lots of engines / gearboxes are assembled with silicone instead of gaskets for a more permanent, leak free joint.
With your silicone up in the hole of the bellhousing, maybe it should have been cleaned out before attempting assembly---?
William Revit

Another vote for Blue Hylomar too, can be tricky to locate it these days, unless you can find an old school independent motor factors. I stopped going to one car spares chain (not Eurocarspares) in the North Harbour part of Ayr when the person on the counter when I asked for Blue Hylomar did not know what it was and when I explained he told me that I did not need it as ‘all the mechanics round here use silicone sealant, the stuff for bathrooms and kitchens’. Made a note to avoid such garages too!

I would always try to get and use the correct gasket (the right material /profile, thickness as well as cut /formed/moulded to the correct shape) where possible with preference for just the gasket depending on the condition of components and surfaces (as clean , flat and as undamaged as I could), as well as gasket availability and quality , and what the application is.

If you are really stuck locating Blue Hylomar and have clips, fasteners, fuel house etc to buy to save on postage then Merlin Motorsport sell it and are quick and efficient with mail order.

Cheers
Mike
M Wood

Thread drift - Greybeard, did I pick up correctly on another thread that you are now retired from your lifeboat mechanic days? It does not seem that long ago that you were asking advice on here about the now often curious/complex/confusing world of job searching, application and selection . Hope you are doing well.

Cheers
Mike
M Wood

I bought some RTV sealant after being recomended it by Ant Anstead on an episode of Wheeler Dealers. Unlike Hylomar or Wellseal which remain tacky the stuff I bought sets quite hard and adheres tenaciously. That's why it was fouling the single rail, silicone would probably have been OK.

However I didn't buy the RTV to use on my car, I needed something to seal some radiator valve stubs at our daughter's house. She has a combi boiler and the slightest leak causes the pressure to drop and the boiler won't light. I have previously tried all sorts of sealant on the radiator / valve connectors without too much success but the RTV did the trick.

We had a Stelrad boiler which apart from the odd thermocouple gave stirling service for over 25 years. Because of energy costs and the impending ban on new gas boilers in Scotland we decided to replace it with a new Worcester Bosch condensing boiler. We got a heating engineer to fit it so it could be properly certified. He advised us to stick with our hot water cistern system. With our system being at least 25 years old and with several cast iron radiators (converted to modern valves) he said a combi would probably need pressurising almost daily.

Jan T
J Targosz

Hi Jan
I had a very similar issue with my daughter’s CH system - I eventually identified it had an automatic vent valve on the boiler. Once I topped up the system stabiliser we haven’t had pressure drop in a year - touch wood - I think the decomposition generating hydrogen that then bled off dropping pressure
timmyk

BMC in their wisdom, and in the Wsm, inform the reader to smear Wellseal on the joining faces of the rear main bearing, before clamping, to avoid seepage. This was upgraded (?) to Hylomar in the Mk2 Sprite Wsm.

Alan Anstead

I've got Golden Hermetite and Blue Hylomar but prefer the Blue Hylomar because it comes off with thinners whereas the Golden Hermetite seems resistant to all solvents I have tried.
MG Moneypit

Two things I know of will shift Gold Hermetite - MEK and Bostik 501 thinner.
Eta: but I still prefer Hylomar. If I remember correctly the patent on it still belongs to Rolls Royce (?).

Mike Wood, you're right - I was deemed surplus to requirement in August last year and pushed somewhat unwillingly into retirement, after 23 years service (6 years full-time).
In fairness I should say that the arthritis has advanced to the point that a seagoing medical might be a bit of a challenge.
I haven't adapted terribly well to unemployment so I'm now looking for a little part time job but as Mrs GB is disabled and dependent on me I can't go back to sea or work away from home.
I do the odd job here and there. Luckily I remembered I was once a mechanic so tomorrow I'm going to Tarbert to sort the steering on a fishing boat, but nothing regular ATM.


Thanks for the kind thought. Hope all is well with you too.

Second edit: I remain grateful to the good people on the BBS for the good advice and encouragement when I was applying for the LifeBoat job. Thanks fellas.
Greybeard

Greybeard
Have a look at U3A ( university of the third age ) there may be a group near you or Active retirement Associations (ARA’s). Depending on your wife’s disability and dependancy it might be something that would appeal to her.

Mens Sheds is something else you might want to look into. There is plenty out there for those that are retired.
Alan Anstead

Room Temperature Vulcanising is completely different to Silicone. RTV has become all the sway in sealing modern engines. Its intended to squeeze out of the joint nearly completely into a groove or a chamfer. That's where it seals. It is reasonably tolerant therefore to relative (shear) movement between the two surfaces.(I sound like the Loctite rep now).
Paul Hollingworth

Thread drift, how I love it!

Thanks for the suggestions Alan. There is indeed a U3A group here. Mrs GB is a member of the U3A choir and the music librarian.
I teach a few ad hoc classes now and then; on hand-tool woodworking, navigation (to RYA syllabus) and occasionally ropework.
Later this year I believe they will be starting a class for conversational Gaelic which I would want to go to as it was in effect my first language. I haven't spoken it in over 60 years but I can still just about follow the Gaelic news on BBC Scotland so it might be nice to get it back.
I was a regular at the Men's Shed project here but it folded after a couple of years. I teamed up with a couple of retired bus drivers and between us we made several wrought steel gates, including making the scrolling tools which I think are still there.
Greybeard

Hi Jan,
In your earlier thread specifically about your t9 gearbox, you also mentioned it was noisy.

What did your box man say was the cause of that? -- if he found it that is.

I approached our local shed project, wondering if there was any interest in old cars. There wasn't, sadly. Or maybe, they just weren't interested in me. 🤣🤣. Had to get that in, before one of you did. 😁😁.



anamnesis

Hi Anam,

Sorry it was remiss of me not to mention the gear box noise. The repairer found a couple of teeth had been rusty at some time. They had been cleaned up and he said the box was fully seviceable though. New gears would have been circ £400 so I will just have to tolerate the hum. He told me this was a common fault with Type 9s caused by water ingress but I've no idea how it gets gets in.

I have also visited the local Mens'Shed. I thaught this could be an option if we moved to a flat without a workshop. I was amazed at the range of tools they had. This included a Myford lathe similar to mine but with a gear box! Most of the tools are donations from widows who are clearing their late husbands' garages. The only down side I could see is that it could be a little like returning to work. You would have to travel there and then tidy up and put your partially completed project away in a cupboard at the end of your session. Also there would be no dirty clothes smelling of brake fluid and hypo oil.

Jan
J Targosz

I am with Willy on this
Peter Burgess Tuning

Peter's back! How lovely!
I agree Peter, but I contend that the problem is not so much with the product it's more to do with the way it's used.
Most people use far too much thinking that more is better, when it ain't necessarily so (as the brothers Gershwin reminded us).
With Hylomar I've found that the barest minimum on both surfaces is good but the crucial thing is to let it dry before assembling.
Walk away. Have your lunch. Pick the grandkids up from school.
Then assemble. Not before.
Most folk that use silicon sealer seem to squirt it all over the place. I wonder why.
Is it because Hylomar is "reassuringly expensive "?
Either way it's good to see you again Peter.
Greybeard

Ah, so it was just noisy teeth Jan. Yep, if not too bad, given the cost, well worth living with, and add a bit more sound proofing to the tunnel maybe.

T9 Water ingress.
Yep it is well known. Remember your box came from a Ford. In a number of Fords, rain water finds its way into the engine bay, at the rear of the engine just above the bell housing, and runs down onto the very joint where your rtv caused a problem.

From there it seeps into the box via the selector rod opening. I had exactly that problem with my Consul Capri. As you noted, the 4 speed is the same construction at the front as the T9, so you get the same problem if the gasket/seal between the bell housing and front of box isn't up to the job. Another good reson for sealant on both sides of the gasket.

But on Spridgets, we don't usually have rain water running down onto that area, so it won't be a problem.

I'm with Grey. I feel assured by the expense of the blue stuff. 🤣🤣.


anamnesis

Hi Anam,

I thought that perhaps my box had laid in scrap yard, in a Capri with no bonnet or even piled high in a heap of other boxes ready for the smelters. The reconditioner said all the bearings were perfect which suggests my box has been reclaimed / rebuilt at some time. Of interest to others who may be considering buying a Type 9 he showed me the offending teeth by shining a light through the cover plate hole. If I was to buy another box I would certainly take a look. Gears are more expensive than bearings.

I understand that Wellseal is owned by Caterpillar and is the only sealant they use. It is also recommended by Lotus for their twin cam engines.

Jan T
J Targosz

"Difference Between RTV and Silicone"
https://www.differencebetween.com/difference-between-rtv-and-silicone/

I wonder how long all our rtv and silicone stuff will kick around long after we are all pushing up daisies.

https://www.quora.com/How-does-silicone-rubber-break-down-how-long-does-it-take-what-would-be-the-by-products-and-would-they-be-harmful-to-the-environment

And what of hylomar and the like?

anamnesis

Thank you Greybeard, never far away
Peter Burgess Tuning

This thread was discussed between 28/01/2024 and 02/02/2024

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