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MG MGB Technical - White smoke from exhaust

My 1980 MGB (42k miles from new) has been used very little recently (240 miles total for last year, less than ten miles each journey). I noticed excessive white smoke from the exhaust recently, also a drop in coolant level, so I suspected a leaking head gasket or cracked/warped head. Cooling system pressure test revealed a small leak from the top hose; sorted that out and a further pressure test held 15 lbs ok over 12 hours. After a 10-mile run the coolant level remained the same. So I guess that rules out any cylinder head defects?

I parked the car on the drive the other day and ran the engine at idle for 30 minutes, after which there was still white smoke at the exhaust and the odd drop of water dribbling out of the tailpipe. It was not a cold day, about 12c. Holding my hand close to the tailpipe for a minute left a clear water deposit on my palm. I'm now wondering if the white smoke problem is just because the car isn't being used regularly, thus allowing the exhaust system to accumulate condensate. The short journeys I do probably don't get the rear end of the exhaust system up to full temperature.

Has anyone experienced excessive white smoke on cars which are not regularly used?
The car's going in for an MOT test on Monday and I'm wondering if the emissions test will be affected by this.
Brian Shaw

Yes, get it hot before the test. Needs 10-15 miles not at tickover. I'd also try to cover the oil cooler for winter use (is it underneath? -mine is easy as it sits in front of the rad.)

I'd think short journeys could well be the cause, but is it smoke or steam?
Michael Beswick

hi,
have you thought of brake fluid. if you put your foot down hard on the brake and hold it for about 30 seconds then start engine, see if white smoke is worse. if so brake servo leaking. had this on my bgt when i had it.
regards bob.
trebor

Michael - I called it smoke but it is in fact steam or water vapour, as seen from most cars for the first few minutes after being started in cold weather.
Brian Shaw

I think that you need to take it on at least an hour long trip, if it is indeed condensation it should burn off in that time.
R. K. Marcks

Every gallon of petrol burned produces more than a gallon of water. If its a cold day the car will steam forever at idle.
Stan Best

Brian-
I have to agree with R.K. Take it for a one-hour run to get rid of the condensed water inside of the exhaust system. Let us know the results.
Stephen Strange

Thanks all you guys. I'll do a one-hour run Monday morning before the MOT and I'll let you know what happened.
Brian Shaw

Hi I have just had my 1974 MGBGT MOT test carried out and the tester said there is no requirement for an emission check
M Scull

The car in question is 1980 which does require emission test.
Michael Beswick

Michael, you just reminded me of something that happened at the last MOT, a year ago:

See if you can figure this out: In the past when I've had the MOT test done, the tester gives me the test certificate, and also a print-out from the emissions test (CO and HC values). Except last year, they just gave me the test cert; I asked for a copy of the emissions print-out so the man at reception went back into the workshop to speak to the tester, then came back and told me "he says you don't need one". I was glad to leave at that point (the car has often been borderline on the HC level so I didn't want to push my luck by querying what he'd said). Now, did he mean that my car (1980) doesn't need to be tested for emissions anymore, or did he mean that along with the new style certificates they are no longer required to supply the customer with a copy of the emissions print-out? Or maybe the tester thought the X-reg car was older than 1980? I'll see if I can get some clarification at the testing station tomorrow.
Brian Shaw

From memory, the emissions test applied to vehicles registered from 1975 onwards.

I haven't heard that it had changed, but I don't subscribe to any classic car publications anymore.
Dave O'Neill2

It's worth checking your engine number, I knew I had an engine out of a 74 in my 76. I showed the tester a print out of the MGB engine data, and he put a note on the certificate validating that the car did not need an emissions test.
c cummins

You might find section 7.3 of this:
http://www.transportoffice.gov.uk/crt/doitonline/bl/mottestingmanualsandguides/mottestingmanualsandguides.htm
useful.
It states:
"7.3 Exhaust Emissions - Spark Ignition" ~
"Vehicles First Used on or After 1 August 1975"

"Vehicles fitted with a different engine must be tested to the requirements of whichever is older, the engine or the vehicle. e.g. A 1995 car fitted with a 1991 engine (of whatever make), test to 1991 standards for emission purposes. Note: The onus is on the vehicle presenter to prove engine age."

So if you car is post 1/Aug/75 then unless YOU can prove the engine is pre 1/Aug/75 then it has to be tested. I don't believe the tester has to give you the emissions figures since the new electronic MoT was introdcued I certainly have not had one since then for any of my 3 cars (2 euroboxes of which 1 diesel and one petrol) and 1 MGB (1970 so exempt :))

Bernie
B Anderson

I'm still getting emissions print-outs for all mine even with the cheapo MOT and for the 73 i.e. visible smoke test only.
PaulH Solihull

Maybe the print out just depends on the garage? It does not say either way in the guide. Not that I can find anyway
Bernie
B Anderson

Good grief! I like the idea of putting an engine in from 1974 in my 1976 car and getting tested for this engine.

As Bernie said, the MoT guidelines state:
"7.3 Exhaust Emissions - Spark Ignition" ~
"Vehicles First Used on or After 1 August 1975"
Surely it must be the vehicle rather than the engine.

That would get short shrift with the German TÜV. They'd be laughing into the pockets of their grey lab-coats!
Mike Standring

Brian, Your car still needs an emission test. My guess is that the tester had binned/not printed the sheet, and had tested cars after yours. To produce one would have meant doing the emissions test again-hence the "you don't need it...."


The MOT "Certificate" is simply a receipt confirming the VOSA records have been updated. Technically you don't even need it! Till you are asked by plod (if he can't check on ANPR).

The emissions paperwork is largely a matter for the garage. It is more likely to be provided to "back up" a failure. Tho IIRC it used to be mandatory to supply diesel gas test paperwork but not spark ignition!

Daft tho it may seem the emissions computer is not "linked" to the main MOT one. The tester inputs the "results" in the shape of a "Reason for Refusal" if applicable. The MOT station has to keep a copy of the emissions for X months. MOT stations are now more aware of the costs-ink jet cartridges, paper etc. It used to be forms and a tatty ribbon!

I used to provide them simply because it was part of the routine. With old vehicles (our) emissions machine asked for the mileage and the capacity of the engine (for the visible smoke test) before you could commence the test.

PS Hope it passed!
Michael Beswick

Mike No it is tested to the older "part". The onus is on the presenter to prove it, not the tester to judge /guess it! and it's a nightmare on the few occasions it happens! Bit like: if the seat belt might fail, remove the seat.....(not the drivers!!)

Grey lab coats huh! I bet the test stations are all in doors with nice heating and exhaust extraction. Our exhaust extraction is the open door, heating is warm clothes. Scraping the ice off before we start, and on and on.....
Michael Beswick

Michael - you're probably right about the tester binning the emissions print-out. I had the MOT done this morning and they gave me a copy of the emissions result. I'm pleased with the HC value of 355 (about normal for a standard B engine) this is the first time since I bought the car in '86 it's ever been below 800! So I must be doing something right. However, the car failed on brakes (not surprising, considering recent lack of use). Reasons for refusal: 001 Offside rear brake binding, 002 offside rear brake recording little or no effort. Garage advised probably rear brake cylinder is seized.
Brian Shaw

Brian, - Sounds plausible! Afraid I regard rear brakes as an annual service item (mine are single line!!) Consider Speed Bleeders when you change the cylinders (assuming they are at fault). Not cheap but make bleeding so much easier and now available in the UK.
Michael Beswick

Michael - I'll have a look at those. Last time I replaced the rear wheel cylinders was 1992, and I used a gunsons Eezibleed (still got it) without any difficulties. When I'd removed the cylinders they looked in quite good condition inside and out, so I cleaned them up, lubed them, and got repair kits and kept them as spares; just unwrapped them and they still seem fine. However, I've ordered a new one from Moss but if it's not here by weekend I'll fit one of my reconditioned ones to get the car back in time for the free re-test.
Brian Shaw

White 'smoke' result:

Probably due to condensation from the exhaust system exacerbated by lack of use and very short journeys. When I took it to the MOT station I went the long way round (despite hail storm in North Wales) and when I got back home there wasn't much visible stuff coming out of the exhaust.
Brian Shaw

This thread was discussed between 11/01/2013 and 16/01/2013

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