What is loud irregular clatter/ rattle on top of passenger side of my engine

20

Asked by Oct 28, 2016 at 05:11 PM about the 1968 Cadillac DeVille

Question type: Maintenance & Repair

   My 1968 Cadillac make a loud irregular clatter/ rattle atop the passenger side of the engine. Mechanic recently changed all rocker arms and bridges due to ticking. Than car overheated on freeway. Mechanic put in thermostat (there was none) changed oil which had turned black and sludge like, refilled antifreeze. Now loud irregular clatter/rattle.  Please HELP!
                                                                         Being Taken For a Ride in MY Cadillac      

6 Answers

35,005

The sludge may have plugged up the hydraulic lifters.

1 out of 1 people think this is helpful.
56,845

On these 472 engines there's no valve train adjustments. All "slack" is taken up by the hydraulic liters. These are very good, long lasting engines. Their only flaw is the plastic "silent" camshaft sprocket. Replace the timing chain set. It's actually common for a Cadillac engine of that era to develop a valve tap if it isn't driven much. Personally I'd have left it alone and just tried driving it more. As for the overheating, it could very well be that timing chain. Especially if you're having late transmission shifting as well. The timing chain will jump at least once before the engine stops running. If this is a higher mileage engine it may be to your benefit to just have the engine rebuilt. Leaded, premium gasoline is required in these engines. Running unleaded over time will damage the valves and seats. You can, when rebuilding the engine, have hardened valves and seats installed so unleaded premium can be safely used. HTH. -Jim

1 out of 1 people think this is helpful.
20

Hi Mark helpful and Jim, Thank you for your responses, but Jim what about the present clatter? Did the mechanic who changed the rocker arm assembly not tighten something properly?. I am reluctant to return to him for several reasons. He seems to not really know what he is doing, but he would never admit it. He is arrogant . Thank you

1 out of 1 people think this is helpful.
56,845

Yes, the present clattering is most likely because the rocker arm pedestals aren't torqued to the correct specifications or a lifter is partially collapsed. Now if it only clatters when you rev up the engine it's most likely a camshaft bearing. Are you running premium in it? If not, the lower octane will cause a spark- knock condition. If properly tuned it should be fine on 93 octane with a lead substitute. You should also be using conventional 10W-30 oil in the crankcase. How is your oil pressure? Any issues there? HTH. -Jim

20

Jim, it is my undertstanding that the valves have been hardened for use of non-leaded gas. I have asked my new mechanic to check for improper installation of rocker arms, damaged lifters and other causes. Thank You very much! selaatyp

1 out of 1 people think this is helpful.
56,845

You're welcome. Glad to help. Pre-1971 engines at GM were designed for leaded gas. Unless, of course, your heads have been rebuilt. Keep us posted. -Jim

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