Ser­vice Bay – Com­mon MoT fails BMC 1100/1300

One of the only BMC mod­els to keep arch ri­val Ford off the top spot in the UK sales charts, the BMC 1100 was a very ad­vanced car for its time and that’s one of the rea­sons sur­vivors should be pro­fes­sion­ally tested ev­ery year

Classics Monthly - - Contents - WORDS & IM­AGES AN­DREW EVERETT

Be­fore putting your ADO16 in for its an­nual test, check out these com­mon MoT fails to save time, money and ef­fort.

In a way this should be an ar­ti­cle rooted in the ‘Seven­ties when the BMC 1100/1300 range – by then get­ting on for well over 10 years old – would be fill­ing up the av­er­age break­ers yard fol­low­ing a cat­a­strophic MoT fail. As bril­liant as it was, and these cars were light years ahead of mod­els like the Viva and An­glia, the ADO16 range in BMC par­lance was known for body rot that was harder to re­pair than just weld­ing a plate onto a rusty An­glia’s chas­sis rail.

Be­cause there were lit­er­ally mil­lions on the road and old ADO16s weren’t worth a lot, most own­ers elected to take the twenty quid from the scrap­yard rather than have their cars re­paired, which is why so few ex­ist. There are very few cars now that are still orig­i­nal and haven’t been welded and the stan­dard of re­pairs varies con­sid­er­ably. This is why the an­nual MoT test really is es­sen­tial on this top sell­ing model, as they had min­i­mal crash pro­tec­tion when new and a rusty ex­am­ple could quite lit­er­ally be a death trap on to­day’s ul­tra con­gested roads.


1100 sills are quite a com­plex struc­ture with a curved outer sill that curved down in cross sec­tion and is spot-welded onto an­other down­ward curved sec­tion. The trou­ble here is that the shape makes a per­fect mois­ture trap and there’s no es­cape for it. To make a good re­pair in this area the best way was to cut the outer panel off, re­pair the in­ner mem­brane and weld a new sill on, but that just wasn’t hap­pen­ing back in 1975!


The Bete Noir of 1100 own­ers and welders of the pe­riod – many turned 1100’s away, as they could be such a night­mare. Rear door open, rear seat cush­ion pulled up and there is the se­ri­ous rot in the rear seat base/heel­board cor­ners. This box sec­tion is com­plex and hard to re­pair, but the rear boot floor mount­ing ar­eas for the sub­frame weren’t quite so bad.


Outer sills were one thing and the in­ners were an­other. Due to the de­sign, – it was such a bad rust trap that Pressed Steel en­gi­neers ad­vised Is­sigo­nis to re­design it (he didn’t) – mois­ture col­lects here and causes havoc. Had the shell been prop­erly rust pro­tected it would have been fine. Re­pair­ing rot­ten in­ner sills will be a se­ri­ous task, as the rest will need do­ing as well.


These aren’t quite as rot prone as on the Mini but they still rust out in the lower sec­tions be­neath the dis­placer. New sub­frames are avail­able and the same rules as the Mini ap­ply. Get­ting the old one out can be a pain of bro­ken bolts and you’ll def­i­nitely find that weld­ing will needed around the mounts. But do it now to a good stan­dard, rust­proof it thor­oughly and the re­pair will be per­ma­nent.


Even the ADO16’s oil leak­ing A-Se­ries en­gine of­ten wasn’t enough to pro­tect this area. The rear mounts for the front sub­frame (on the front toe­board) rust away and are not easy to re­pair, as there is the main floor sec­tion and the re­in­forc­ing plates in the way. Mois­ture gets in be­tween the two and re­sults in a mess but to make a good re­pair you need to drop the sub­frame slightly (not too dif­fi­cult) and re­place both bits.


The most com­plex and Avant Garde bit of the 1100/1300 was iron­i­cally the most re­li­able. How­ever, the old­est 1100 is now 56 years old and the pipes can rust and burst but that’s not so com­mon. That’s just as well, as you’d need to drop the sub­frames out to make a re­pair if that hap­pens. New pipes are avail­able but check for leaks where the dis­placer hoses fit – they can be re­built.


There won’t be many 1100/1300’s left on the road to­day that haven’t been welded up some­where dur­ing their life­time.

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