I've looked at several threads where people have reported similar symptoms, and the Buick shop manual discusses the identical issues:
- Start-up cold start = clacking, rattle sound under valve cover that goes away after a few seconds of engine operation from cold start.
- rattle and clacking sound comes back after engine heats-up and oil pressure (viscosity) drops.
Shop manual solution is to pull intake and remove lifters for inspection of faulty lifters for leak-down test.
Other recommendations in this forum:
Check oil pressure
Change oil for ATF and run car at idle for 30 min with ATF. Remove ATF and put engine oil back in car.
Add Seafoam to crankcase engine oil and run car at idle for 30+min or longer.
I have good oil pressure 70+ at cold start, and 25 psi idle, 65 psi 2000 rpm once engine is warm.
I've tried ATF, and the engine is very quiet idling with ATF for long periods of time. Changing back to engine oil (15-50w) caused the valve train rattle to return after 15 min of driving normal conditions and when oil viscosity dropped the oil pressure to 25 psi at idle.
Changed oil for ATF again and drove the car low rpm for 15 min with ATF, and no valve train rattle (ATF pressure was 15 psi at idle and 45 psi at 2000 rpm). Valve train rattle does not happen with ATF in the engine. 15-50 w oil back into the engine and valve train rattle (cylinder #2) returns again under same conditions as before; 15 min of normal driving. oil pressure 25 psi idle/ 65 psi 2000 rpm.
Added half a pint of Seafoam to standard engine oil. Initial rattle on cold start, but goes away after a few seconds. The engine idle is quiet with no noticeable rattle sounds from passenger valve cover. Ran quiet at idle for 30-40 min. Engine cold-start next morning had small rattle noise that goes away after a few seconds. Drove car 15 min - good oil pressure - and rattle from passenger valve cover returns.
In this case, the noisy passenger valve train symptom has not been eliminated by these engine cleaning methods, so time to pull intake, mark the lifters, check the camshaft for excessive wear, etc. I'll try the lifter disassembly, cleaning and leak-down test in the shop manual. Hopefully i don't have to replace the camshaft.
- Start-up cold start = clacking, rattle sound under valve cover that goes away after a few seconds of engine operation from cold start.
- rattle and clacking sound comes back after engine heats-up and oil pressure (viscosity) drops.
Shop manual solution is to pull intake and remove lifters for inspection of faulty lifters for leak-down test.
Other recommendations in this forum:
Check oil pressure
Change oil for ATF and run car at idle for 30 min with ATF. Remove ATF and put engine oil back in car.
Add Seafoam to crankcase engine oil and run car at idle for 30+min or longer.
I have good oil pressure 70+ at cold start, and 25 psi idle, 65 psi 2000 rpm once engine is warm.
I've tried ATF, and the engine is very quiet idling with ATF for long periods of time. Changing back to engine oil (15-50w) caused the valve train rattle to return after 15 min of driving normal conditions and when oil viscosity dropped the oil pressure to 25 psi at idle.
Changed oil for ATF again and drove the car low rpm for 15 min with ATF, and no valve train rattle (ATF pressure was 15 psi at idle and 45 psi at 2000 rpm). Valve train rattle does not happen with ATF in the engine. 15-50 w oil back into the engine and valve train rattle (cylinder #2) returns again under same conditions as before; 15 min of normal driving. oil pressure 25 psi idle/ 65 psi 2000 rpm.
Added half a pint of Seafoam to standard engine oil. Initial rattle on cold start, but goes away after a few seconds. The engine idle is quiet with no noticeable rattle sounds from passenger valve cover. Ran quiet at idle for 30-40 min. Engine cold-start next morning had small rattle noise that goes away after a few seconds. Drove car 15 min - good oil pressure - and rattle from passenger valve cover returns.
In this case, the noisy passenger valve train symptom has not been eliminated by these engine cleaning methods, so time to pull intake, mark the lifters, check the camshaft for excessive wear, etc. I'll try the lifter disassembly, cleaning and leak-down test in the shop manual. Hopefully i don't have to replace the camshaft.
