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 MGA - Exhaust smell while driving

I've had my 56 roadster since last fall but didn't get a whole lot of driving in before putting it away for the winter. It's been out of storage for about a month now and with the nice weather I've been able to get it out with the top down several times now. What I've noticed is that there's an exhaust type of smell in the cockpit while driving. Hopefully this isn't a stupid newbie question, but am I correct to assume that this isn't normal? I think I'll have bring it somewhere to have the exhaust system checked for a leak, but just thought I'd check in here first in case I'm told that such a smell is normal for these old roadsters.
Andy Bounsall

Andy

You may have noticed that the firewall has quite a number of drilled holes in it. Those that don't have cables or pipes running through them should have rubber bungs. Any 'open' holes allow blasts of hot unhealthy air through from the engine compartment. If you also happen to have an exhaust leak within the engine compartment this could help explain why you can smell exhaust fumes in the driving seat.

Another source of air leaking from the engine compartment is at the joints between the firewall vertical section and the outer skin. These gaps are most prominent at the outer edges of the scuttle (Forward of the windscreen posts up underneath the instrument panel).

Steve
Steve Gyles

Andy,

Most likely, you have an exhaust leak. I would start at th exhaust manifold and work my way back. With the engine running, you will normally feel the exhaust pressure with a naked hand. Careful... it's hot. Pay specific attention to the exhaust manifold gasket, the donut between the manifold and the down pipe and all the other connexions.

If you can't figure it out, send me an e-mail. Look at the location... we are probably neighbours.

Karl
Karl Leclerc

Andy:
I had the same problem with my coupe after I first bought it, and, as Steve suggests, I soon noticed that most of the empty holes in the fire wall were missing their blanking plugs. Even some holes with cables running through them needed fresh grommets, as the old ones had shrunk and broke and let air through. It's not to hard to replace the grommets with the cables in place, if you cut the grommets properly.

Anyway, installing the blanking plugs and replacing some grommets greatly reduced the problem.

The other source of the smell was leaky carb gaskets, causing fuel to drip onto the hot exhaust manifold. After these gaskets were replaced, the smell completely disappeared.

Hope that helps.

Regards,
M.D.
'57 Coupe
M. D.

Andy,
In a dark area place a light source under the hood near the firewall. Then go into the dark cockpit and look for bright spots. Mark each light leak with chalk or marker, then go back and fill the marked areas with the appropriate grommet or a dab of silicone. Takes a couple hours to do it right but the results are worth it.
Also be sure the rubber boot on your shifter is intact. A lot of engine fumes can pass through there.
Bill
Bill Boorse

Thanks very much for the quick feedback folks. Some good tips and suggestions. I'll have a look later this week to see what I can figure out.
Andy Bounsall

You may not have an exaust leak. It could be the fumes comming from the crankcase vent tube. Unlike new car where the crankcase is vented into the intake system, these old cars vent the crankcase out into the atmosphere thru the vent tube on the side of the engine. It reminds me of many of the old cars I had when I was younger, the more blow-by, the more "motor odor".
Ed Bell

Ed

Just as an aside, I have vented my crankcase back into the intake system. I rotated the front tappet inspection cover through 180 degrees so that the pipe pointed upwards and then connected it to the front airfilter with a rubber pipe via a Y piece inserted into the rocker cover breather hose. It's been working fine for the last 8 years.

Steve
Steve Gyles

Steve,
I didn't think the tappet covers were symmetrical.
Bill
Bill Boorse

Bill

I should have said that I am running an 1800. However, I seem to remember doing something similar with the 1500. Just had a look at the 1500 on the floor in the garage and I have the cover in place the other way round to normal. This was purely to keep my modified pipework away from the exhaust manifold.

Steve
Steve Gyles

Don't forget the battery cover! If that's not well sealed, you'll get any fumes coming off the engine AND the fumes from exhaust pipe tip (there's a bit of suck back in certain situations).
Regards,
JoeM
'56 MGA
JFM

This thread was discussed between 11/05/2005 and 17/05/2005

MG MGA index

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