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MG MGB Technical - sill waxing
|I want to inject some waxoyl into the MGBGT sills. Can anyone tell me where the best access point is. Do I have to drill any holes? The car has stainless steel cover plates on the sill top. I could drill under there if necessary.|
|R E Merrall|
My BGT was Ziebarted from new. When it was about 5 years old I decided to check out the sills, and removed the aluminium sill kick-plate and cut two 1” holes in the top of the sill to give access for inspection. No rust was visible. I then decided to fill the sills with oil. I blocked all drain holes (temporarily) at the bottom edge of the sill and poured in a pint or so of engine oil. The oil soon started to leak out further inboard from the floor panels and I dealt with this by wiping the oil away and sealing the gaps. Eventually I got as far as filling the sill with oil with no further leaks. It was messy at times – I put some polythene sheeting down to catch the oil. I left it overnight and then drained the oil, and then did the other side. It’s now 30 years since I did this and the sills are rust-free except for some minor stone chip damage on the outer surface. Also, I am now able to remove the kick-plate and inspect the sill interior (small dentist’s mirror and bright led).
Warning: Cutting a couple of 1” holes in the sill makes your car (technically) an MOT failure. However, MOT inspectors are not allowed to remove/dismantle during the test.
|The sill consists of two separate compartments divided by an internal steel divider or membrane. This membrane is the first bit to vanish when rust starts. On my car it was almost non-existent, but hopefully yours will be fine.|
With a flexible spray tube attached on your sprayer you can get into the inner part through the holes in the strengthening rail that you can see under the car, the so-called castle rail. To spray inside the outer part I drilled two holes about half an inch diameter. I drilled up from underneath the outer sill on the small horizontal part, one at each end of the central sill section. My probe was long enough and flexible enough to get the length of the sill from those holes. I plugged the holes with rubber plugs. Six MOT tests have passed and they have never been mentioned.
|I ued waxoil when I restored my 67 back in 2005. What is the recommended time to reapply this?|
|Bruce TD4139 Cunha|
|Here's a sketch I did to show the construction of the sill. You can see the two separate chambers. Spraying into one side only will not affect the other. You must inject on both sides of the membrane.|
I used Dinitrol 3125 as I think it creeps better than Waxoyl. Waxoyl is best diluted with white spirit. Ideally you want an air compressor so that you can use a Schutz type can and get a powerful spray.
As to when you should re-apply - who knows? In theory it is in a closed box section, so where's it going to go? I did mine in 2008 and haven't repeated the exercise yet.
|Mike - you may find my earlier post (from 2002) interesting (see BBS Archive "MOT failure ?!"). This describes what happened when my car failed its MOT (due to "deliberate modifications to outer sills").|
I appealed against the MOT failure, and the car was re-tested by Vehicle Inspectorate who upheld the original tester's interpretation of the rules.
I did something similar, but not quite as extreme as Brian. I stoppered up all the drain holes and first used a liberal supply of Dinitrol which I left to creep and splash about as I used the car. After a few weeks I chose a hot day (yes they do exist!) and then injected dilute Waxoyl, did the same sloshing exercise then sprayed with undiluted Waxoyl . Sloshed around again then removed the stoppers. Since Waxoyl is thrixotropic I didn't get much dripping!
|Thanks for the advice. I read Brian's archive with interest; perhaps the best course is to speak to my garage before drilling holes. I'll let you know what he says.|
I was under the car yesterday and could not see any drain outlet for the heater air intake below the windscreen. Where does this exit?
|R E Merrall|
|Many cars seem to have a hole in the outer sill top near the A-post. Drill another in line with that in the inner sill top to deal with that side of the central membrane.|
At the rear of the door opening, just aft of the seam where the C-post starts to rise up from the sill, drill two more holes. The outer one will go through two layers - the C-post and the sill - and allows you to protect the join of those two as well as inside the sill itself.
Also remove the splash plates in the wheel arches aft of the front wheels, and the side trim aft of the doors, and that will allow you to protect the outsides of the sills and the insides of the wing cover panels, which are usually the first to go, as seen here http://www.mgb-stuff.org.uk/sill.htm#1. But don't use Waxoyl here as it is too thick, will bridge the very narrow gap between sill and cover panels, which will trap moisture. I have used clean engine oil with a strip of card poked in the gap to distribute. Yes it drips - but only initially, whereas for a few years the sills may well drip Waxoyl whenever it gets hot.
See here for sill construction and drainage http://www.mgb-stuff.org.uk/sills.htm#1
|How interesting Brian. A case of applying the rule book against all logic. You would think that if the tester and inspector thought sensibly about the way the MGB is constructed they must realise that the outer wing, front and back, is simply a decorative panel. But when did sense come into the process. As for the comment that if you had oversill panels, you would pass - well that just shows how illogical the rules are. I've never liked oversill panels because they can hide all manner of rust. I wouldn't consider buying an MGB with them fitted.|
The bottom of my rear outer wings are held with stainless screws and nuts and not welded, just like the front wings. My local garage tester has never commented on those fastenings nor the rubber plugs on the bottom of the outer sills. I think I'll keep going to the same place!
|Paul – “But don't use Waxoyl here as it is too thick, will bridge the very narrow gap between sill and cover panels, which will trap moisture.”|
This is what I believe to be the cause of my sill problem. Although the car had been Ziebarted when new, after about 5 years I noticed the paint blistering near the bottom of the rear wing, where it overlaps the sill. When I removed some of the paint I could see pinholing so I then cut a 1” hole in the wing to investigate. The Waxoyl had failed to get through the narrow gap between wing and sill – this was confirmed when I removed the interior trim card and tried poking a hacksaw blade down towards the sill.
Rod – My other MG has a similar ‘modification’ – a 1” hole near the bottom of the rear wing, which I have plugged with a rubber blank. This allows me to occasionally check in there for rust. It’s been like that for many years and there’s been no problem with MOTs. As far as the MOT failure goes, I think in hindsight I should have just taken the car elsewhere and paid for another MOT.
Mike – That was the first and last time I used that MOT station.
|Spoke to my local garage owner who said a couple of small holes in the top of the sill to allow access for a spray tube would not be a structural or mot issue!|
|R E Merrall|
|Paul do you have any pictures of the holes so I can be sure to get them in the right place.|
|R E Merrall|
You refer to splash plates; don't know if you have the Moss catalogue, but it that the same as baffle plates referred to on page 100? Looking at my car there are flexible covers held on by half a dozen bolts at one side and a rubber seal at the other Is that the splash plate you refer to?
|R E Merrall|
|Paul is referring to Item 3 in this picture from Moss on-line catalogue. They call it a baffle plate. It has a rubber seal around the edge - part 5 in the picture. It is fixed by 4 or 5 bolts on its inner edge. There is also a top section with seal - parts 6 & 8 in the picture.|
It's function is to prevent water and muck from being thrown from the front wheel into the cavity between the wing and the footwell. These plates can be very rusty and hard to remove with seized bolts.
|Rod - see attached. Both my cars came to me with the hole at the hinge end, and this car came with a plugged hole just aft of the tread plate (which covers the join between sill and C-post). A drilled a similar hole in the other car, and grommeted it.|
I drilled similar holes in the inner sill in the other car. This one has the original-style rubber sill covers, they could be original and so no holes, or could have been removed and replaced hence holes under them.
I see what you mean about the narrow gap and good advice about using engine oil. But what a mess! I tried your method of using card and it worked fine but I found it difficult to get good coverage back towards the door. My solution was to use a pump (notmally used to extract oil of my jeeps diff) to pump oil really far back. This seems to have done the trick. Now for the other side. I'm really grateful for the advice from you all. Cheers.
Small point, nobody piked up on my earlier question about the location of the drain from the air duct in front of the windscreen. Anybody know?
|R E Merrall|
|Sorry I meant to find something to help. The heater has a drain on the right-hand side (driver's side in the UK) and it comprises of a rubber tube up beside the gearbox. The tube terminates in a rubber bulb (often referred to as Tom's knob) with a slot in the end. The theory is that the closed slot keeps fumes out of the cabin, but that the pressure of water in the bulb opens the slot and allows the water to escape. The bulb can easily become blocked with leaves and other cr*p that enters the intake in front of the screen. Poking something through the slot usually clears it and gets you an arm covered in all sorts of unmentionable rubbish.|
In my photo, taken while modifying my GT to take an injected V8, I have drawn a green box around the bulb so that you can see where it is located. You will only be able to see this if you raise the car up safely and crawl right underneath. Please make sure it is properly supported before you do this.
|"and gets you an arm covered in all sorts of unmentionable rubbish"|
Which when mine got blocked and there was water visibly lying in the box I did it from above :o) Photos here.
Prod gently, better with a straightened wire coat hanger to begin with perhaps, the spigot can rust and snap off which means water runs into the double-skin section over the tunnel, and can mean significant surgery with the heater out to repair.
|Paul, that won't work on earlier cars. They have a bigger baffle in the heater box and the top of the drain is out of sight and inaccessible.|
This might also help.
|H J Adler|
|Here's a picture of Tom's knob taken from below, with engine and 'box removed. You can see the heater blower motor to the left of the picture.
|Dave O'Neill 2|
|This is some of the 'crud' that I found hiding in there.
|Dave O'Neill 2|
|On my rubber bumper roadster, which has the hole accessible from above, I recently used one of these 'flexible waste pipe cleaners'...|
It worked a treat.
|Dave O'Neill 2|
|Perhaps someone could help me with my confusuion. As I understand it the inside of the sill diaphram can be sprayed through the holes in the castle rail, and the outside of the diaphram through the hole in the top of the sill near the hinge if the car has one(which mine does). If the sprayer extension is long enough I take the whole of the sill and the ouside of the diaphram can be covered through this hole. Since it seems that the B post can be accessed through the opening behind the trim panel aft of the door on my BGT why do I need to drill 2 holes in the top of the sill at the base of the B post?|
|R E Merrall|
|It's a fair question, that hadn't occurred to me. I just followed what Lyndsay Porter advises when MGBs were new to me 26 years ago.|
For that matter you also have several drain holes under the outer sill to get to the outside of the diaphragm, as well as the seemingly standard hole on the top by the hinge.
|With my extension probe neither the hole on top of the sill, nor the outer sill drainage holes were big enough for the probe to go in. That,s why I drilled the two discrete holes in the bottom of the outer sill. From them I could spray the entire length inside.|
|An article in North American Classic MG issue 63 mentions filling the rockers with closed cell building foam. Can't quite get my head round that idea. Suggests extra strength if hit on the side.|
The foam injection was doing the rounds in Germany about 30 years ago in DIY magazines. It does stiffen the car, at least at first.
The problem is that water gets in between the foam and the steel of the sill. I assume the rates of thermal expansion of building foam and steel are different and the foam slowly but surely comes unstuck. Capillary action does the rest. Anyway, whatever the process is, you end up with a car which has rusted through and is impossible to repair!
Air is vital to the survival of the metal. You need to keep water off and if any does get in, it must be able to run away and dry off as quickly as possible.
|Michael, that diagram looks familiar. My '81 reg. roadster's previous owner had the car treated with Dinitrol when new; the locations of the panel drillings on the diagram are the same as on my car. It's been almost rust-free in the 30 years I've owned it (bit of rust near the bottom of LH door, and on the top-of-wing beading).|
|The SSV MGB of 1972 does have sills filled with structural foam. But then longevity wasn't an issue.|
|Thanks for all your help. I have almost finished waxing, just the doors to do.|
|R E Merrall|
This thread was discussed between 13/08/2015 and 30/08/2015
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