Author Topic: catastrophic bummer  (Read 5014 times)

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Offline 3929R

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Re: catastrophic bummer
« Reply #15 on: Wednesday,March 11, 2015, 10:19:20 PM »
Mark
Salt Lake City, Utah, USA

Offline EuropaTC

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Re: catastrophic bummer
« Reply #16 on: Wednesday,March 11, 2015, 10:55:25 PM »
In conclusion..... I'm more befuddled than before.

 :)   me to ! 

I thought HealeyBN7 had caught it with the servo/booster idea but if you don't have them I'm back to square one.  My Elan has compressions in the 155-160 range which is very similar to yours and plods along ok, so as long as they are consistent I wouldn't worry too much just yet. I've also changed both cars to a slightly hotter plug, again on advice from the Elan forum, which does run cleaner.

The only time I've seen oily smoke was due to worn valve guides, but that problem was a long time coming and pretty obvious - very noticeable when you put your foot down after a short period on overrun/trailing throttle.

A few random thoughts - do you have the crankcase breather connected and feeding into the carbs ?  How much oil does the car actually use ? 

Brian 

Offline 4129R

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Re: catastrophic bummer
« Reply #17 on: Thursday,March 12, 2015, 12:24:03 AM »
Have you checked the level of the brake fluid in the master cylinder?

I think brake fluid is a hydraulic oil, so would burn bluish.

Offline blasterdad

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Re: catastrophic bummer
« Reply #18 on: Thursday,March 12, 2015, 03:47:01 AM »
The seals on the brake MC were shot (as were the slave cylinders). I assumed the boosters were also toast so I removed them and swapped in a Datsun F10 master cylinder. I also plugged the booster vacuum port on the intake manifold. I never drove the car with boosters but really can't see why you'd want or need them. The car is so light, as far as I can tell it seems to brake great without them.

^^^^^

The booster theory has been ruled out...

Offline jbcollier

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Re: catastrophic bummer
« Reply #19 on: Thursday,March 12, 2015, 05:54:18 AM »
Time to do some careful testing.  Start with a hot compression test and then repeat with a shot of oil in each cylinder.  Lotus twin cams are commonly a wee bit smokey, usually from the guides.

Offline 3929R

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Re: catastrophic bummer
« Reply #20 on: Thursday,March 12, 2015, 08:55:53 AM »
Looking at the video I posted of the car's exhaust from last night, would you call that a wee bit smokey? or woefully smokey?

Could bits of gasket or other such flotsam have temporarily plugged an orifice in the oil pump or elsewhere, causing a spike in oil pressure, in turn causing a surge of oil to blow through valve seals? Is that even a possibility? Might explain the plume and current smoke if the seals were damaged.

I'm planning a hot compression test and draining/changing the oil to see if any bits are in it. Dependent upon the weather I had plans to sail on Friday/Saturday and ski on Sunday. So I may not get back to the garage for a week.

Once again, thank you all for the feedback.
Mark
Salt Lake City, Utah, USA

Offline BDA

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Re: catastrophic bummer
« Reply #21 on: Thursday,March 12, 2015, 09:45:25 AM »
That looked like a fair amount of smoke to me. My thought when I watched the video was that it might be steam because it looked white, but it was hard to tell. I don't think a spike of oil pressure would cause oil to leak past the valve guide seals.

Someone may probably need to correct me on this, but I THINK that valve guide seals or valve guides generally produce more oil smoke on when you let up on the gas because I think you would have less pressure in the port. I don't really have a lot of experience with worn guides or seals. I believe there should be a vent in the cam box and if that is plugged up, that could force oil past the seals and guides.

In any event, when you do the compression check dry and compare it to one where you squirt oil in the cylinders, you'll be able to rule rings in or out.

Offline EuropaTC

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Re: catastrophic bummer
« Reply #22 on: Thursday,March 12, 2015, 10:20:44 AM »
causing a surge of oil to blow through valve seals? Is that even a possibility? Might explain the plume and current smoke if the seals were damaged.

In the all important quest for lightness, uncle Colin left out the valve seals.....   :)

Being serious, there aren't any. You just have the cam bucket over the valve stem/spring and then a cast iron valve guide. So you'll always get a touch of oil going down there and burning, unlike more modern engines which might have seals ahead of the guides.

I watched the video and couldn't make my mind up. Like BDA I thought it more whitish than dense blue, but it's a difficult thing to photograph and get the colours on screen exactly as you're seeing them in real life.  My car will produce smoke like that before it gets up to temperature and even at temperature if I let it idle and then rev it up to 3 or 4k then you'll see smoke. I don't think it's a sign of impending doom (fingers crossed ! ) because it's always done that, in fact they both do. It's easy to compare with a modern engine and think it's falling apart, but these were designed before emissions and are going to burn some oil.

The engine sounded all right on the video so here's hoping there's no real crisis. As John says, a hot compression test is probably the next useful step, but if you're getting 140 cold and more importantly within 5-10psi between cylinders then I think you're all right there. 110-120 or a big drop on one or two adjacent cylinders is when I'd start to wonder.

Valve guides I do know about because I did them on the Elan. Before I'd stop at traffic lights for a minute and there would be a diesel engine cloud behind me when I took off.   Also coasting downhill on a trailing throttle tended to suck oil in and when you put your foot down you'd see a puff in the rear view mirror. The car ran ok though and it was only embarrassment at the looks I got from other drivers which pushed the job to the top of the list.

Brian

Offline 4129R

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Re: catastrophic bummer
« Reply #23 on: Thursday,March 12, 2015, 11:24:20 AM »
All sounds like a modern 2 stroke to me !

Offline BDA

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Re: catastrophic bummer
« Reply #24 on: Thursday,March 12, 2015, 03:20:13 PM »
I agree with Brian. There is almost certainly nothing actually catastrophic going on so that should be a relief. It does seem like it is the valve guides. Interesting that they are cast iron! I would have thought they were bronze. I would think bronze guides can be had and I would think they are better than cast iron, but I really don't know the practical difference. I also seem to remember that the guides are shorter than optimum so they do wear out quicker than they might (as has already been said).

What happened to the idle and the power? From the video, it didn't seem to be running poorly.

Offline jbcollier

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Re: catastrophic bummer
« Reply #25 on: Thursday,March 12, 2015, 09:03:42 PM »
If the head gasket blew, it would blow a cloud of white smoke with a slight sickly-sweetish smell.

Offline Roger

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Re: catastrophic bummer
« Reply #26 on: Friday,March 13, 2015, 05:04:51 AM »
The vacuum pipe is still there. Where does it go?

Offline BDA

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Re: catastrophic bummer
« Reply #27 on: Friday,March 13, 2015, 06:32:49 AM »
If the head gasket blew, it would blow a cloud of white smoke with a slight sickly-sweetish smell.
Couldn't the gasket fail at an oil passage and thus cause blue oil smoke? Or is that less likely for some reason?

Offline BDA

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Re: catastrophic bummer
« Reply #28 on: Friday,March 13, 2015, 06:34:31 AM »
The vacuum pipe is still there. Where does it go?
I believe there is only one vacuum pipe - on the manifold for the rear carb. That is for the boosters.

Offline TCS4605R

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Re: catastrophic bummer
« Reply #29 on: Friday,March 13, 2015, 11:59:06 AM »
Mark,

A couple of things come to mind.

I understand you have removed the servos, so that problem can be eliminated.  If the diaphragm inside a servo fails, the brake fluid can get sucked into the engine via its connection with the intake manifold and the engine burns it - happened to me some years ago before I removed my servos.

There is a rubber 'tube' that connects the head to the block.  The tube is located on the right hand side of the engine in front of the mechanical fuel pump.  If it gets clogged up, oil cannot drain from the head back into the engine sump.  This excess oil could then be sucked into the combustion chambers via the intake valve stems and cause a lot of smoke.  Have you taken the cam cover off?  You should be able to poke a long skinny screwdriver or welding rod down the tube and touch the bottom of the sump pan.

Other than that, it could be worn intake valve guides or a broken ring.  I have a 1958 MGA that smoked a lot some years ago and used a qt. of oil every 500 miles.  When I disassembled the engine, the rings were not only broken, but had worn a groove up to the top of the piston and half of the top ring was gone - evidently jettisoned thru the exhaust valves and out the tailpipe.

Do a leak down test on a hot engine with all plugs out and each tested piston about 10 degrees short of top dead center - a piston at top dead center may be just close enough to starting down that the rings move to the top of the piston ring groove - you want to avoid that - you want the rings resting on the bottom of the pistons grooves.

Have you changed the oil lately - any metal fragments (looks like silver dust or larger) in the oil?

Tom Berkeley
75 TCS - 4605R