76 Eldorado Mis- Fire Trouble.

[Bud63]

Hi, I'm new here and hope you guys and help with some insight regarding a car that belongs to a friend of mine. The car is a 1976 Cadillac Eldorado convertible with a 500 Cubic inch engine and approximately 86,000 original miles on the clock.  My friend purchased this car last June in the greater New York City area.

At the end of December, a local and at the time reputable shop in Connecticut took the car in for an overall evaluation. The shop was asked to look safety and reliability issues since my friend only had the car for 6 months and was not completely sure of the cars background and history. Overall it looks very original and not molested in anyway. It's also 40 years old with typical wear and tear but overall looks decent.

The shop took for ever and a day just to get back to him with the evaluation. I was not until February the shop said the car was in decent shape, needed some work on the breaks and also the front left spindle in the Axel needed to be replaced.  The spindle came from a donor car in Rhode Island and after more than 2 weeks it was complete.

However, now the shop is saying there is a misfire. At first I thought with this car sitting for more than 2 months in the frigid temps down to minus 5 degrees and almost 3 feet of snow, that perhaps the issue was electrical in nature.  However, the shop claims to have checked all the wires, distributor cap, spark plugs and claims the issue is there is no compression coming from the number 5 Cylinder.

I'm curious why the number 5 Cylinder would suddenly not have any compression?  I drove the car in December and it ran smoothly and seemed to have plenty of power.  I know the car is 40 years old, but overall the car was not abused or driven hard and with only 86,000 miles on a 500 CI engine, that should be nothing.

Any ideas what would cause this cylinder to suddenly go dead? 

Any insight will be helpful.

Thanks
Bud

[35-709]

Stuck valve?  Have YOU or your friend driven the car?  If so, can't the miss be felt, if there really is no compression in a cylinder it should be easy to feel and hear in the running of the engine.  Maybe you have a stuck valve from the car sitting outside for a long period.  If it really does have a miss, try a pint of Marvel Mystery Oil in the oil and drive it some.

I am seeing a red flag being waved here, maybe another trustworthy shop in your area recommended by a fellow Cadillac owner on these forums should take a look at it. 

I for one would never let my car (be it nice or a beater) sit outside a repair shop in the dead of winter for 2 months waiting for a relatively simple inspection that isn't much more than what is accomplished during a typical NYS vehicle inspection.  In my opinion that car should have been brought back home when it became obvious the shop was in no hurry to do as requested and arrangements made for an inspection elsewhere.  Unfortunately, that is water over the dam.
   

["Cadillac Kid" Greg Surfas 15364]

Ditto Geoff
Greg Surfas

[Scot Minesinger]

Agree with first post as well, emphasis on major red flag - a convertible sitting outside all winter, I cannot type my reaction and what would I think of the place that did that to my car.  Any place that is "trusted" and leaves a convertible outside by definition is not.

[76eldo]

I agree take it somewhere else.  They a prepping you guys for a rip off non repair.  Some shops will paint your valve covers and tell you they did a valve job.

If it has a misfire it could be just a plug or a wire issue.

I would not trust this shop.

Brian

[Bud63]

Thanks everyone for your input. I agree this shop is not to be trusted.  Every-time I called they had an excuse at to why they did not get the job done to the point where it became embarrassing. And I also agree this car should have never been left outside, I was told by one of the owners at the beginning that he was keeping that car inside the garage only to have him tell me a month later he had to dig it out of the snow.

When I drive the car at the end of December the engine ran fine, it was smooth with plenty of power. The only issue is it had a slight "dieseling" after you turned it off, but it was very slight. The shop said the carburetor was fine and needed nothing and no mention was made of the dieseling when he did the overall evaluation.  The misfiring is new and I have to agree that it's most likely a sticking valve due to it sitting in the cold for so long.

Were going to work on getting the car out tomorrow and to another shop where I know the owner personally. At this point, my friend is considering suing the current shop, if there is any damage done to the car from sitting outside. 

I'll keep everyone posted and thanks again for your input.

[76eldo]

I would be very surprised if it is a stuck valve.  Others will chime in here, but I think stuck valves are much more common on flathead type engines.  All my cars sit for months at a time over the winter and they all start up fine.  Sometimes my 60 taps a bit until the lifters pump up.

One a 76 engine a stuck valve is not common.

These guys could have crossed two plug wires to make it miss if they think they have a sucker that will pay for unnecessary engine work.

Get it out of there and count your blessings.

Brian

[James Landi]

Just one more point beyond all of the great ones made already.  If you have a bad missfire -- perhaps created by some criminal behavior, I would NOT drive your car, but have it "flatbed" and hauled  somewhere. Swtiched ignition wires can create a timing chain failure, and then you're into big money. If you can't diagnose and fix the issue on the lot, truck the car away, and don't run the engine.  And herein is the big issue you face.. just where?  I my experience driving old Cadillacs for decades, very few mechanics will be inclined to be especially helpful.  Finding the right PERSON to work on this car will either make this experience pleasurable or a continual nightmare. 

[James Landi]

By the way, if the subject car was moved in and outside without sufficient warm up, and if the pvc is not operating well, it will RAIN on the inside of the valve covers, and rust can hold open a valve... thus creating a 0 compression scenario.  I've experienced this condition with an OHV Continental engine.

[Scot Minesinger]

Further to James's first post about finding the right mechanic.  I never could.  When I bought my 1970 Cadillac in 2005 planned on paying others to work on it and soon discovered situations like this and out of necessity had to work on it myself.  In the DC metro area it is the third largest population center in USA, and no luck with mechanics. 

My business partner's wife's brother is in drug rehabilitation about age 35 and is currently training to become an auto mechanic out of necessity because he has never held a job before.  Many auto mechanics become one not as their first career choice and are not dedicated.  The good mechanics have all the business  they can handle and are keeping their skill a secret with their good clients.  This is not a bash on all mechanics, just half of the seemingly available ones that are terrible and are without knowledgeable references.

My consulting business turns away business and only takes on new clients as referrals.  I get it.

I am my own mechanic whenever possible now, and it is quite satisfying.  Figured if others less fortunate than me could do it so could I.  Plus I am an engineer, reading a wiring diagram or vacuum diagram is easier than reading instructions on an aspirin bottle.  You do not have to be an engineer, many engineers do not know how to drive a nail with a hammer.  The secret is don't guess, don't rush, use common sense, don't force anything plastic, and above all read the darn shop manual.  Strongly suggest that your friend become his own best mechanic, after all this time he could have read the manual cover to cover and had a bunch of advise from this forum.  Take an adult education class on auto mechanics at the local high school and bring the car in as the project.  Got to start somewhere.

[Jon S]

A sad story indeed!  I would get that car flat bedded out of there ASAP.  It's quite possible the mechanic has set it to mis-fire on purpose or out of sheer stupidity.  I concur . . . do not attempt to drive it until a competent mechanic goes over it!  A comedy of errors!

[Bud63]

Apparently the issue is a broken valve seat on number 5.  With only 86,000 in the clock this seems odd to me, unless sitting in the cold had something to do with it? 

Apparently this repair is going to require removing the head and having it rebuilt? What should a repair estimate be on a job like this? Should he have both heads rebuilt at the same time so everything is in sync?

 

[James Landi]

Just a guess, but I reiterate, a valve stem is likely rusted and one of the valves is hanging upon... because the engine was briefly run in very cold conditions and not permitted to burn off all the condensation in the value covers... so it rained inside your engine and a valve is hanging up.   Valve seats broken?  I think that's a mis-diagnosis. 

[54 caddy larry]

town auto in waterbury ct. just did my 54 331. they only do the machine work no wrench spinning. boil the heads, new exhaust seats, new freeze plugs, full valve grind and mill the tops of the guides to accept new style valve guide seals ran me $375. been doing business with them for years and never had a problem, very knowledgeable old school car guys. i repeat you have to pull the heads and bring them in. hope this helps.
Larry

[savemy67]

Hello Bud63,

Remote diagnosis is difficult under the best of circumstances.  I tend to agree with James L., and would be skeptical of the diagnosis without knowing exactly how it was determined.  I also agree with Scot M. that good help is hard to find.

A compression test and or a cylinder leak-down test are two simple and inexpensive tests that can to done to see if there are problems with rings and valves in any cylinder.  I encourage you or your friend to find out what tests were done to determine that cylinder 5 has lost compression.  If a broken valve seat is the case, it may be the result of a defective casting (less likely), abuse and overheating by previous owner(s) (more likely), or a combination of the two (most likely).  Of course, while the car may look good, you have know way of knowing how the engine was treated over the past 40 years.  Again, find out what tests were used to reach a diagnosis of a broken valve seat, and then ask a trick question:  intake or exhaust?  Unless the shop has dropped the exhaust Y pipe at the exhaust manifolds, the shop should not be able to answer this question.   Be sure to have your hidden camera   Good luck.

Respectfully,

Christopher Winter

[James Landi]

Bud,

You may have to go the route that Larry suggests... but if #5  truly has zero compression, I'd add the Marvel oil (as suggested in a much earlier previous post) and let the old gal gently warm up (DON'T RACE the engine) for ten or 15 minutes. Simply warming up the engine, gently, may break the valve stem free w/ the Marvel oil.  If not, and if I'm right, the other  fix might simply involve removing the valve cover, identifying #5 cylinder, and spraying "Blaster" at the two valve stems, and then giving the rockers some gentle taps DIRECTLY over the stems and see if they move in response to your taps.  The final test would have you get both valves in the closed position (#5 cylinder in the firing position of the cycle) and then detecting if both valves are equally closed after your tapping them-- might have a feeler gauge handy for this process.  In my experience this is not always "the fix," because I have had to "go the route" Larry is suggesting, since I was unable to get the valve stem freed up because of the rust that had formed on the stem and the valve guide was too far gone. I don't think you need new valve seats... however, you're not wasting money doing the work Larry is suggesting... valve guide seals usually need replacing (age), and some of the other work he's suggesting--it's  worthy of your consideration. I am certainly not an expert, but I have run into issues like this before, when my car was briefly run in an out of a heated garage and into super cold temps and not permitted to heat up and cook of the condensation that forms primarily on the valve covers.  I do hope you have good news for us...James

[James Landi]

Bub... just one more point.. it was made previously-- make sure the suspect cylinder is getting spark!  If you trust the folks who did the compression test, then it's likely that you have spark and no compression, and the problem is with the one of the two valves.  YOu state that it ran smoothly and well when you brought it there, so beyond a plug wire or spark plug, and with zero compression, your issue is a valve that is not closing.n

[54 caddy larry]

I was just giving you an idea of cost for a reasonable full head job. with that said you have a lot of diagnosing to do before you start pulling heads off. on top of all the other good suggestions you may need to look at worn cam, bad lifter or something simple like bad spark plug. you stated broken seat, has this been verified
Larry