Lotus Elan

Odd Puffs Of Smoke

PostPost by: tdafforn » Fri May 13, 2005 8:43 am

Hi guys,
Ever since I have owned my +2 (3 years) I have had an intermitently smokey exhaust. It generally doesn't smoke excessively, and doesn't smoke on start up. Just at the odd time when I stop in traffic I can see it in my rear view mirror. The engine runs with good oil pressure (>30Psi at idle) and the compressions are within 5lbs across the 4 cylinders (average of 180lbs). The compression is unchanged when I add oil to the cylinders. The head was rebuilt by the previous owner <10000 miles ago and I have a reciept which includes new guides and seats. The only other thing I have noticed is that when I see smoking at the rear I also get a puff out of the engine breather (Observed when running without it attached). I think the smoke is oil smoke although it is not intense enough to really tell, although the guy who MOT'd it thought it was running a little rich.
At the moment I am not too concerned as it isn't effecting the performance, and next winter may be engine rebuild winter anyway!
Anyone have any thoughts?
Cheers
Tim
1972 +2S130
User avatar
tdafforn
Fourth Gear
Fourth Gear
 
Posts: 867
Joined: 12 Sep 2003
Location: Kenilworth Warwks.

PostPost by: Alasdair » Fri May 13, 2005 1:34 pm

If you have a brake servo, could very well be brake fluid as it can be drawn in cylinder after a stop, puff of smoke on take off.

Overhaul time for servo perhaps?

Alasdair.
Alasdair.

1953 David Brown Cropmaster
1954 S1 Land Rover
1962 Elite S2
1966 Lotus Cortina MK1
1968 Elan S3 SS Coupe
1968 Austin J40
1969 Elan S4 SE DHC
1972 Elan Sprint
Alasdair
Second Gear
Second Gear
 
Posts: 113
Joined: 23 Mar 2005
Location: Oakville, Ontario, Canada.

PostPost by: types26/36 » Fri May 13, 2005 1:35 pm

T.C. engines have large clearances combined with modern engines and that includes pistons and valves, in standard form there are no valve seals and unless you want to follow the route Keith has described in other posts it is unlikly you will get a totally smoke free exhaust, you probably do have a little valve/guide wear but if the car is not useing excessive oil dont worry about it.
One other point, if the brake servo is passing brake fluid into its vacuum chamber you can also get smoke (white) but you should see the fluid level going down.
Brian.
Brian
64 S2 Roadster
72 Sprint FHC
User avatar
types26/36
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 3655
Joined: 11 Sep 2003
Location: U.K.

PostPost by: Hegg » Sat May 14, 2005 3:46 am

If it helps, mine does the same. I received similar responses that it's a common occurence due to larger clearances and no seals and all that.

My smoke is dark, not white. Oil seems to stay high for an acceptable amount of time (given the other leaks I have on the block, but that's another story).
1970 Lotus Elan +2, 1991 Lotus Elan, 2006 Lotus Elise, all for sale.
User avatar
Hegg
Second Gear
Second Gear
 
Posts: 55
Joined: 27 Jan 2005
Location: Salt Lake City, UT, USA

PostPost by: tdafforn » Sun May 15, 2005 8:02 am

Hegg,
Thanks for that, makes me feel a lot better...
Servo is fine ( and pretty new)
Cheers
Tim
1972 +2S130
User avatar
tdafforn
Fourth Gear
Fourth Gear
 
Posts: 867
Joined: 12 Sep 2003
Location: Kenilworth Warwks.

PostPost by: steveww » Sun May 15, 2005 9:58 pm

A little bit of smoke is quite normal. No valve guide seals don't forget. Just keep an eye on oil usage, they are supposed to burn a bit, I think the manual gives figures for this???? Don't forget to allow for the oil falling out of the bottom ;)
User avatar
steveww
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1838
Joined: 18 Sep 2003
Location: Northamptonshire, England

PostPost by: tdafforn » Tue May 17, 2005 11:10 am

Hi,
Thanks for all the suggestions,
I am currently running 20 50 castrol.
decided to Spend some of the weekend driving the +2 and monitoring the smoke. Observations are:
Doesn't seem to be smoking any more!
Only change was to lean out the mixture a little as she seemed to be running a little rich.
Mixture screws at 1 1/2 turns out and she runs fine which makes me think the idle jets are a little fat?
Changed to the next richer jets from stock when I got the car as it seemed to be always running lean (lots of poping from the carbs). Rebuilt the carbs this winter, and now perhaps we're running too rich.
Also have noticed that the engine seems to return to idle from revs a little slower eg. 1300 -700 rpm in 4-5secs, springs are all tight, anyone any ideas?
Will put the leaner jets in anyway.

Still get a reasonable amount of smoke from the crank breather, but have plumbed it back to the air box.
Cheers
Tim
1972 +2S130
User avatar
tdafforn
Fourth Gear
Fourth Gear
 
Posts: 867
Joined: 12 Sep 2003
Location: Kenilworth Warwks.

PostPost by: Hamish Coutts » Tue May 17, 2005 11:59 am

Folks,

As a general rule -

Black smoke - too much fuel
Blue smoke - oil
White smoke - probably brake fluid

Hamish.
:)
"One day I'll finish the restoration - honest, darling, just a few more years....."
User avatar
Hamish Coutts
Fourth Gear
Fourth Gear
 
Posts: 517
Joined: 29 Jun 2004
Location: Scotland.

PostPost by: steveww » Tue May 17, 2005 4:14 pm

I thought is was

Black smoke - too much fuel
Blue smoke -oil
White smoke - Red Arrows :lol:
User avatar
steveww
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1838
Joined: 18 Sep 2003
Location: Northamptonshire, England

PostPost by: Matt7c » Wed May 18, 2005 7:36 pm

I don't understand (again!). How does the brake fluid make white smoke, and where does it come from? :blink:
1965 Elan S2
Matt7c
Second Gear
Second Gear
 
Posts: 190
Joined: 01 Aug 2004
Location: Gloucester, England

PostPost by: types26/36 » Wed May 18, 2005 8:17 pm

If the seals in the servo cylinder become defective the fluid gets drawn into the vacuum chamber and then gets sucked into the inlet manifold......white smoke.
Brian
Brian
64 S2 Roadster
72 Sprint FHC
User avatar
types26/36
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 3655
Joined: 11 Sep 2003
Location: U.K.

Total Online:

Users browsing this forum: No registered users and 22 guests