MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Waterfall in Cockpit

Continuing the joy of discovery on my new '70 B. Hit my first real rain on the way home from work today, and was surprised by a stream of water on my left ankle. While pleasant given the day's humidity, I'm nonetheless concerned. I recall reading that several others have had this problem, but I don't remember the source, or solution. As far as I can tell, there is no leakage around the windshield. Could the water be coming through the cowl vent? A friend with a vintage Mustang solved that problem by bolting a piece of thin plexiglass under the vent. Has anyone tried this with an MG?
Scott C

Scott,
Leaks could be from a number, or combination, of sources. Assuming you are correct in ruling out the windscreen, check:
fresh air flaps in sides of tunnell, just under the dash - if the chamber is blocked, water could be building here and back=flowing,
firewall wire/tube and steering rack rubber seals and grommets - as these age they fall out, or may just be missing,
the master clutch/brake master cylinder box cap for a correct seal. Whilst you should not have a problem here in normal rainfall circumstances, there is a chance that severe splashing could be reaching the area. The clutch and brake pedals rise through the top firewall area there and ther is no gasket, system relies on a seal of the master cylinder box cover.
All the best
Regards
Roger
Roger

Scott,
Unfortunatly, there is an old adage, "you can tell what the weather is doing outside your MG because it will be doing it inside as well"! Try everything listed above and good luck. I travel with 2 large chamois clothes for extreme rain (left ankle, left thigh!)most of the leaks have been sealed for normal rain, but thunderstorms & sustained heavy rain needs the chamois! Going through Oklahoma 2 years ago during toranado season was fun...
Good Luck!
Robert Dougherty

Well I was in your shoes two months ago. I have now moved from a waterfall to more of a babbling brooke when it rains. What I found out was the the bottom of the windshield, basically where the metal corners meet originally had a seal. Well over the years this had disappeared, wore out or whatever but it wasn't there. So I would get water coming in the corners and going down the little tray behind the dash and then right into my shoe. I cauked this are and now I am down to a small flow. I know that the areas around my peddles leak because when I washed the engine bay I had a nice flood in the enterior.

Hope this helps.

Josh
Josh

Scott,
virtually all MGBs use a "plenum" air chamber to take in, and as best as possible, separate fresh air from water. This is the box you can look into thru the vent just ahead of the windscreen. They have a variety of metal rain deflectors which are supposed to drain the water away from the fresh air intakes for the interior fresh air vents, and also keep it out of the heater box.

At the bottom of this plenum, there is a drain hole and tube (under the car at the top of the trans tunnel, just behind the bellhousing) to allow the water to escape as it comes in. This tube usually has a short tube with a bulb on the end, supposedly to keep fumes from returning via this drain into the air stream.

However, this bulb often hardens and also gets filled with debris, and causes the water to simply back up to a point where it will overflow the lips of the air vents, and come on in and dowse your feet and make rust of your floor boards.

If you look carefully down thru the cowl air vent, you should just be able to see the drain on the RH side of the plenum. Take a piece of doweling or metal rod/tubing and poke it down into the drain and simply purge it of the debris. A small trickle of water from a hose can aid in clearing the crap out of the drain. If you find that the bulb end has hardened, making it difficult to clear even with a stout rod, then jack up the car, put it on stands, crawl under the car and either replace "tom's knob" or do a Lorena Bobbit to it and have a more reliably clear drain.
Hopefully this will help you find your problem. Let us know if you find another source, as all experiences are helpful. Cheers!
Bob Muenchausen

A couple of other sources: Check the rubber washers at the base of the windscreen wiper shafts; Check to see that you have a rubberseal around the lip of the engine bay across the back(windscreen end) and about 1/4 of the way down the side toward the front. My 72 roadsster didnt have one and water would run down inside the engine bay and onto the shelf the pedal is on and then inside the car.
william fox

Scott, what are you complaining about? If you had a RHD car you would be getting wet on your right ankle - much much worse, believe me!
Matt

I can't address the source, but I can offer a solution.

I use a magnetic cowl vent cover which has reduced (though not completely) the amount of ankle soakage I used to experience. I bought mine from Moss (http://www.mossmotors.com/cgi-bin/db2www/mossmotors/MossUSA/shop/ViewProducts.mac/report?T=40657&PlateID=3122&ModelID=31000).

Though it says that it's not for use while the car is in operation, I'll use it when it rains (hardly ever).

Ann
1979 MGB (daily top-down driver)
Ann

There is a drain tube at the bottom of the void under the vent cowl, this frequently gets blocked up with leaves etc, this will allow water to over flow through the footwell vents. You can clear this out from above or below with something like a straightened coat hanger, its more effective from below but watch out for when that water flows, it'll stink. that should solve most of it but you'll never get them completely dry, good luck.
Raymond Love

Scott,

Another suggestion:although you say that there may not be leakage around the windshield, do check the rubber seal at the base of the windscreen pillar. When living in Louisiana, where it rains an inch an hour, I eventually tracked a leak to that location. What happens is that the water running off the windscreen pools in the corner and seeps under the pillar grommet into the car and runs down the footwell to where it can drip on your ankle.
There is no need to remove the windshield (one of the worst jobs on the car - particularly putting it back with new rubber!), just lift the edges and squeeze some sealant in.
Kevin Kelleher

Ann, that magnetic vent cover is a cool idea but it might not work on a 70B. I have a 70GT and the bonnet is aluminum. Magnets won't stick to it :)
Simon Jansen

Sorry. Long day. I've gone stupid. The cover is over the vent (in the steel in front of the windscreen) and NOT on the Aluminium bonnet of course! Time to go home :)

Simon
Simon Jansen

Well anyway , now you know why MG's tend to rust from the inside - out ! :-) .

-Nate
Nate

Not a waterfall of water by any means, but don't forget to replace the gaskets under your windscreen wiper bases. I used to get water in that way, as well as all the others already mentioned.

You don't want to fix all the leaks though. Otherwise you'll be too dry, and insufficiently acclimated, when it comes time to lie on the ground and whack the fuel pump.
Terrence Goodell

Just a quick note... even if the gaskets under your wiper bases are there, they won't work if the nuts are loose. We had a loose nut on our '71 LHD roadster and water just poured in. Half a turn on it (when we realised what the problem was a year later...) and the inside of the car is totally dry.

fwiw.
--
Olly
Oliver Stephenson

Thanks all, for the responses. Contrary to my first inspection, the culprit (or at least one of them!) appears to be seal at the windshield pillar. Further investigation will continue over the Fourth of July (Matt, that's when us LHD guys celebrate the success of our "rebellion" some years ago) weekend when I intend to undertake a journey behind the dash (various bulbs out, possible bad voltage stabilizer). Ann, the magnetic strip should be here today from Moss, thanks for the info that it will stay on at speed, I had planned to test the theory anyway!
Scott C

Scott,

I've got the same problem. In a strong rain, you can actually see a trail of water running out of the seam in the window pillar. It dribbles down the dashboard and drips off onto my left leg. I managed to slow it some by putting some silicone sealant on the outside of the windshield, where the lower left corner disappears into the rubber gasket. But it still leaks in a downpour.

Since that time I found out 3M makes a product just for this sort of thing. It's more liquid and flows into the seams and cracks. It's called "windshield sealant" or something like that. I haven't gone searching for it, but you might start at the 3M web site to get a real name or part number for the stuff. I got the feeling it was being phased out, as modern windshields seal differently and don't use this stuff. So don't hesitate (like I am).

Best wishes,

Matt K.

(BTW, I use my magnetic vent cover all winter too. I've yet to lose it, even on the interstate at 75 mph.)
Matt Kulka

This thread was discussed between 26/06/2002 and 01/07/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.