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4 mechanics, 3 totally different diagnoses: potentially an engine knock?

Two days before moving across the country in my 2001 Toyota Corolla, after some routine maintenance (recharging air-conditioner, bleeding breaks, etc…) my mechanic called to tell me there was a knock in my engine, potentially a rod-bearing, and my car would need a new engine (for $4,300). I immediately started crying as there is no way I can afford that repair. The mechanic said the car could potentially still make it to California if I drove slowly and added oil regularly. I drove the car to California, added less than one-quart of oil, and it made it the 3,500 miles. I immediately took it to a mechanic an oil change/check up, they said there was no problem with the engine and the car was in great shape (now with 129,000 miles). I have no idea what an “engine knock” would sound like, so I trusted them. When I took the car for the CA smog/emissions test, the mechanic performing the test said he could hear a knock (and it could likely be a rod bearing) and that I should consider trading in the car soon, but I definitely shouldn’t take it on any more long drives. Today another mechanic diagnosed a problem with the top of the engine (not the rod bearing) from getting an oil change at one of the cheap-o-lube places. They said the gun that deposits oil into the car had broken some part where they put the oil in and that had damaged some gasket. The repair for this was only $120, so I told them to do it. I’m not convinced that there isn’t rod-bearing damage, but how can you test this? Should I trust the car enough to drive on a long road trip?

At one point about 8 months/6,000 miles ago the car stalled and blew it’s spark plugs. I took it to the nearest shop (via tow truck) for repair, and then to my regular mechanic (the first one in this story) afraid of engine damage and both diagnosed it as having nothing wrong (after replacing the spark plugs).

So, should I get rid of this car? I can’t seem to find another Honda/Toyota as new or in as good of shape with low milage for under $7,000. Should I get a new engine? Should I just try to trust this car and drive it until it explodes?

What would you do in my situation? I have no money, plenty of debt, and I’ve now had lots of conflicting diagnoses and contradicting second opinions.

Can you tell us more about repairs involved with "At one point about 8 months/6,000 miles ago the car stalled and blew it’s spark plugs. "

Did you tell these mechanics what to look for?

  1. Use the Mechanics Files tab on this website to find a trusted local mechanic. Some of the ones you’ve used in the past sound dubious. And don’t go to any quickie lube places.

  2. Check your oil level weekly and make sure it’s always topped up.

  3. Ignore all diagnoses of engine knocks, etc, until you yourself hear the engine making unusual noises. Until then, keep driving. And don’t let anyone sell you a new engine until the current one breaks :wink:

If you really had a bad rod bearing, you wouldn’t have been able to drive the car 3500 miles across the country without the engine throwing a rod. Your story reminds me of the problem my dad had with his 1939 Chevrolet back in 1949. The engine in his Chevy did have a knock. One diagnosis was a bad rod bearing. These old Chevrolet engines were splash lubricated and had babitt bearings, so this could have been a possibility. A second diagnosis was a bad timing gear. Chevrolets of this vintage had fiber timing gears and were noted for this problem. However, the real problem was a slightly bent dipstick for the oil. Each time the crankshaft came around, one of the throws would hit the dipstick. A master mechanic fixed it for free–laid the dipstick on the concrete apron around the gas pumps and staigtened it out with a couple of whacks with a hammer.

Yes, I did tell each of them about the car stalling and blowing spark plugs (it only happened once after being parked/neglected for months), and I have the print out from the mechanic that explained the diagnoses and the repair. I was shocked, that it was only around $100 for this repair because all the mechanic did was change the spark plugs and give the car an oil change, ran it for a while, and said it didn’t seem to have any damage to the engine. I do still think this is where the problem must have originated, because otherwise I’ve never had a problem with the car.

I’ve shared with each of them the previous mechanics’ diagnoses. Both the mechanic here and my primary one back east were honest and trustworthy and have 4-stars in the mechanics files tab on this website (it’s a great source for people who move a lot!).

Just drive it. If it made the cross-country trip, there can’t be too much wrong with it…

You stated that before you made the move that the mechanic told you to drive carefully and add oil regularly.
Does this mean that the engine was very low or out of oil when he made this comment?

If so, then it’s possible there could be a subtle engine knock. Sometimes they’re hard to hear and a year or so ago I had to give someone bad news along similar lines. The good running car they just bought had a very, very subdued rod bearing knock that they had never noticed and it was near impossible for me to hear unless I leaned way over the engine and listened carefully.

Today another mechanic diagnosed a problem with the top of the engine (not the rod bearing) from getting an oil change at one of the cheap-o-lube places. They said the gun that deposits oil into the car had broken some part where they put the oil in and that had damaged some gasket. The repair for this was only $120, so I told them to do it.

Whoa! They broke something and had the cajones to charge you to fix it? I’m almost speechless. BTW, there may be one mechanic at a fast lube joint but even that’s a stretch. Most have no mechanics on staff. Those guys are trained to do simple fluid exchanges…

+1
They worked at McDonald’s two weeks before. Even fluid changes they can screw up, as is clear from the OP’s experience.
It is best to never go there.

Putting this in chronological order,
A) 6000 miles ago your engine stalled and “blew its sparkplugs”. Can you be more specific? Did the sparkplugs come out of the engine, lose their ground electrodes, or what?
B) Since that event, you’ve been intermittantly told that (1) the engine has a top-end knock, possibly a rod bearing, and (2) the engine is A-okay.
C) you’ve been advised that some foreign object was left in the engine after an oil change and it has caused engine damage.

The problem is that there is no way to check for rod bearing damage without visually inspecting them. That means a teardown. Understand that there is no relationship between the condition of the rod bearings and oil usage. You can have a bad rod bearing and not use oil. Or use oil and not have a bad rod bearing. The two are unrelated.

I don’t know if yo could drive cross country with a damaged rod bearing. The danger would be that the bearing might seize, but the fact that it did not does not mean it isn’t doesn;t have damage. The damage might be minor and still cause a mild knowck.

Honestly, I would just keep the oil level up, keep driving it, and keep an auto club card and a cell phone handy.If it seizes, it seizes. If it doesn’t, just keep on keepin’ on. You have nothing to lose IMHO.

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If you had a rod knock, you would definitely hear it. Rod knock is very loud and sounds like someone hitting an anvil with a sledge hammer, the sound you would hear in a blacksmiths shop. You could have the beginnings of a timing chain failure, but that could take another 60k miles before it has to be addressed. It will also make a lot of noise when it is about to go.

If you had an engine knock from pre-ignition, you would not have passed the smog check in California. The noise could also be from a valve lash opening up, but on this engine, that is hard to adjust so I’d leave it alone. As long as you can hear it, its not doing any harm, unless it gets real loud.

If you are still using 5w30 oil in your engine, I would recommend that you change to 10w30. I don’t recommend that you go heavier than that, but at over 100k miles, its the best oil IMO. Any brand that is certified by the API is OK.