500ci intermittent lifter tick rough idle

[hotrod095]

'76 eldo with 100K original miles. I have noticed an intermittent lifter tick especially when cold. I try to start her up once per week but lately it has become noticeable. This is not a constant loud noise. I did have luck adding 1/2 quart of marvel mystery oil a few months ago which eliminated the noise and I noticed the performance had returned. Sadly now, even with that MMO in the crankcase I hear the noise and it has a slightly rough idle with popping out of the tailpipe. This typically goes away after about 30 minutes of brisk driving but it is plaguing the car at start-up. Any suggestions short of tearing the head off? 

[James Landi]

Frank,

I note that you start your car, and I assume, let it idle during winter storage. Your practice appears to be intuitively correct; however, it's truly a very very bad idea. Unless your engine is provided with a sufficient driving distance, and under load, you're creating a lot of condensation in your engine... that's accumulating and causing rust and sludge.  I pass on this information and advice to you as the topic has been discussed on this forum before.  As a "shade tree mechanic" for many decades, I can attest to the destructive mess that's created in short cycle gasoline engine use.  Using the Marvel Oil is good practice, but nothing less than a long drive without 'heavy footing" the gas pedal will likely cure your sticking lifters.  Hope my comment simulates other members to weigh in on your issue.    James
"

[hornetball]

Most valvetrain components can be viewed/inspected/replaced by simply removing a valve cover.  To remove lifters, you'll need to remove the intake manifold.  There's no need to remove a head unless you find an issue with the valves (I found chewed-up valve stems on my '74).

[Big Fins]

Rarely, will you ever find Cadillac lifters going bad. Even at 100,000 miles. Put your money on the rockers themselves. They wear at the valve stem contact point.

[V63]

A couple suggestions:

With mention of a popping in the exhaust there might be a sticking valve, try adding  marvel (4oz for 10 gal) to the FUEL. If your area uses alcohol blended fuel it degrades in months ...verify the fuel is fresh, a classic sign of stale fuel is sticking valves....followed with seized valves in their guides. A valve not Fully returning (closing) adds to clearances that the lifter cannot compensate and therefore a Ticking noise results.

Could the car be flooding...too rich cold?

A leaking fuel pump can introduce fuel in the crankcase and that can  dilute the oil to cause a ticking noise. This would be less of an intermittent issue.

[MaR]

I had a wiped lobe at ~50k miles in my '74. If you go to the trouble of removing valve covers, you can check the lift of the cam lobes to see if any of them are worn.

[signart]

^^^^^^^^^^^^^^^
Yep, this above. Particularly the intake lobes, if it's poping on acceleration.

[hotrod095]

Rarely, will you ever find Cadillac lifters going bad. Even at 100,000 miles. Put your money on the rockers themselves. They wear at the valve stem contact point.

I hope you are indeed correct. Also forgot to mention I have been adding 4oz/10 gal MMO into the fuel. I don't think it's a wiped lobe due to intermittent symptoms. I let it run for about 40 minutes one evening after driving home and then went for a brisk drive and it idled like a dream and had plenty of pickup. I have read before that the big block Cadillacs and notorious for low oil pressure. I do not think its a matter of a lifter "going bad" maybe just not enough oil made it down the passage to the lifter on the far side near the firewall.

I want to keep this thread going for future reference. I plan on pulling the valve covers soon when I get a warm day to inspect the rockers and will give an update.

[James Landi]

I'm glad to know that you're going to keep the thread going, because it's not an uncommon challenge.  I am respectfully suggesting, though, that you give yourself an opportunity to experiment a bit more by specifically altering your winter start up regime, as follows:  1.  Don't run the car at idle... take it on the road when the weather permits, and simply drive it (lovingly) for ten miles to provide a thorough warm up which will allow the PCV to pull out all of the moisture in the engine and the oil.  I think your issue, which may to be a stuck valve stem and potentially a lifter and or bent push rod, might respond well to a new regime.  If you decide to open the valve covers, pay close attention to any valve that does not "slap" shut when you push and release the spring tension on each valve stem--- this would be indicative of some rust on the valve stem that is hanging up the valve and NOT allowing it to close shut (at times). Then take note of any push rod that does not rotate when the engine is running--- that's a tell tail of worn parts in the hydraulic or a push rod or rocker arm.  Hope this helps,  James

[71 Fleetwood]

Ditto on James' advice.  My experience has not been with 472/500 engines but this is a common symptom with the other 1960s and 70s brands that I have stored. When I put the car on a regular monthly driving schedule the symptom has disappeared.  Hopefully, your car will respond to the extra attention and fresh air.

[hotrod095]

I asked my mechanic who is used to working on cars of this vintage. He is telling me to run 2 quarts of ATF and top off with clean oil and filter, run the car for 3-5 minutes at 2000rpm, then change the oil and filter again. I am nervous about doing this and don't want to damage the bearings. Anyone have experience with running ATF?

[V63]

ATF is effectively the same principle as marvel mystery oil. I substitute it frequently. It is an old technique. I personally prefer to not exceed one quart per crankcase.

[James Landi]

I, too, am familiar with this old school approach.  You might consider installing a mechanical oil pressure gauge under the hood so you can assertain the base line oil pressure (when up to temperature) before you add the "flushing agent," at idle and at 2000 rpms  (by the way, when hot, these engines may only push less than 10 pounds of pressure--- that's normal).  Just my opinion, so don't take "it to the bank," but I don't think you'll do any damage, and I think the recommended "flush" may cure the issue.  Rust on valve stems can be hard to break though, so you may have to perform some diagnostic surgery, depending, off course, on whether you can cure the issue with the flush and a new approach to winter starts and runs.  By the way,  I've owned big block twin engine gas powered boats for decades, and I've never started them up during the winter lay ups.  Last year my boat was launched after a 3 year slumber--- I cranked both engines without applying ignitiions for maybe  20 seconds, and both started and idled without any odd mechanical noises--- all this is to say, you can do  much more harm by starting winter stored cars and not putting them under load and driving them for 10 miles or so, to get all that nasty condensation out of the insides.   Hope this helps,   James

[35-709]

"... you can do  much more harm by starting winter stored cars and not putting them under load and driving them for 10 miles or so, to get all that nasty condensation out of the insides."

My 2 cents --- totally agree with James Landi and others who have mentioned this.

[TJ Hopland]

Another question is how long have you had this car and how much have you driven it?   We sometimes hear stores like this and find out this is happening with about 10 miles of driving on a car that stat a long time.   That's way different than having this issue suddenly come up on a car that you regularly drive.

A minor issue like this I would just get fresh oil in it and and put some highway miles on it.    I have had many cars that ran 100x better after some fresh oil and burning a couple tanks of fresh gas on the highway.   

[hotrod095]

All good suggestions here.. I have the car 6 years. It was my uncles who purchased it in 1996 from northern Michigan. To our knowledge, only the driver's side head gasket and water pump gasket was replaced. In 2020 I did the passenger exhaust manifold (huge job by the way!) but other than that, the engine has not been opened or overhauled. I noticed that since adding MMO the oil is the dirtiest I have ever seen for only 2k miles of use. 

The car is not driven much and when it is, its typically around town. The most use the car will see in from June through September. I am renting a garage for it now that is 15 minutes from my new home. When I had the car in my garage at the old home, I would start and drive it more regularly. Now that I am commuting to the garage, I am more apt to just start it and not drive so far, maybe a few blocks. These cars need "work" as I was told by a friend. They typically don't rev above 2200rpm on the street due to low end torque.

Thanks to everyone for input. I am going to give the ATF a try and then change oil and filter, then go for a decent highway drive about 45 minutes to an hour and will give an update. It has not broken 30 deg in New York for about a week now, except for one day that was rainy and damp so I haven't had a chance to get the car out and about.

[James Landi]

Frank,

THis is a good plan.  If all goes well, the engine will provide reliable service.  A word of caution:  we're all tempted to push these 1/2 century old engines and running gear to their limits,"Let's see what it will do." I grew up with used Cadillacs, and learned (the hard way) that simply driving them with respectful tenderness and love, that they'll run well for decades.  If pushed to their limits, something major and very costly will break. Another suggestion: the original specifications for tire inflation limits tire pressure to the low 20 psi.  There's a noticable improvement in road isolation if you run your tire pressure as recommended.  Fact is that tire pressure under 20 psi is potentially dangerous, however, the Cadillac recommended psi is marginally above that inflation.   Keep us in the loop with your car., and when you have time, post some pictures.  In the meantime, stay warm and safe.   James
'

[hornetball]

You NEED to replace the timing gears.  I would avoid driving much until that's done.  When you do that, you can inspect/refresh your valve train.

https://forums.cadillaclasalleclub.org/index.php?topic=154660.msg424523#msg424523

[35-709]

Those pressure recommendations in 1976 were for old style radial tires, if you are running modern radial tires, the absolute minimum would be 28 psi for that heavy car and even that is too low.  Radial tire construction (and materials) is not the same as it was in the mid-to-late '70s and pressures back then are not proper for today's modern radial tires.  The generally accepted pressure for automobile radial tires is 32 to 35 psi (check the driver's door jamb for recommended pressures on any car with modern radial tires).

[Pmartin2204]

I had similar issues and I ended up just swapping the heads on my 500 with a set of rebuilt heads I had. Problem solved. I believe one or more valves were burnt due to having bad valve seals. Just throwing this out there.