CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Engine Knock Issue

Coming home from my in-laws in Missouri, my wife’s Catera starting knocking/tapping. It sounded like if the engine was low on oil and the valves were slapping. Stopped and checked the oil and it was about a half quart low so I topped it off. No change. We were about 10 - 15 minutes west of Huntington so we headed off. Called the local Cadillac dealer and made arrangements to have it checked the next morning. I went over and it sounded awful like a diesel engine instead of the six cylinder under the hood. Long story short, they couldn’t tell without tearing into it and I didn’t have 2 weeks and $6K for the used engine he wanted to put it. Had my brother come tow us to my Mom’s in VA. My brother had a “mechanic” friend come over and while they were checking out (running) he said they hear a “snap” and it started running rough. I am at my wits end and want to get this fixed if it isn’t going to be too expensive. Cars specs are as follows: 1999 Cadillac Catera, V-6, Auto, 89,000 miles. Please help!!! JP

Ok, a couple of things I forgot. (1) Oil pressure actually went up when the “incident” happened {Oil pressure is normally around 40 but it went up to almost 80}; (2) Still have some power but I did not push it; (3) This happened last July and it has been parked since. I have been told that (1) it sounds like no oil is getting to the top half of the engine; and (2) it may be a rod/valve issue or a “spun” bearing (?). JP

Remember this is a $2500 car at best despite nameplate or mileage.

It sounds expensive.

Is this a "BabyStar engine? (overhead cams).

You have 2 choices…Sell the car for parts or locate and install a salvage yard engine. You should be able to find one for less than $1000…Google “Used Cadillac parts” and do a nationwide search for an engine…

Since the oil pressure actually went up as indicated by the gauge, and it sounds like the engine is being starved for lubrication, I wonder if there’s some kind of restriction preventing proper oil flow. It does sound like the pan should at least be dropped to try and determine what’s going on here.

Stupid question though: Have you tried installing a different oil filter?

My brother and a mechanic tried to do an oil change thinking the same thing. They replaced the oil filter and ran a high detergent oil through the system. They did a test run and while it ran he said they heard a pop and it immediately started running rough. They shut it down immediately. I am beginning to wonder if perhaps the timing belt/chain broke. Is the oil pump cam driven? If so, if the chain/belt skipped would that cause the original symptoms? I am truly baffled at this point. . . .

Solved the problem: sold the car. Now someone else who has the money and time can figure it out. My wife is looking at cervical spine surgery and it is the least of my problems. So it is gone. It was a great little car; just a bad engine.