Brief Knock at Start-Up, Then Low Oil Pressure at Idle When Warm

The TV news the other night had a segment about a lady with a 20 year old Toyota Camry (I think) , claimed to be still running perfectly with over 500,000 miles. When the obvious question was asked, she replied she didn’t do anything other than taking it to the shop for its normal maintenance schedule and when something unexplained occurred, noises not heard before, etc. They interviewed the smiling shop tech “yes, she’s a great customer, always brings her car in on schedule”. TV news didn’t mention it, but the fact she’s driving 25K per year probably has a lot to do with it also, freeway driving is very easy on a car.

Someone else owned it for the first 70,000 miles. I changed the oil every 3000 to 5000 with a high mileage 5W-20 synthetic oil and NAPA Gold oil filters. My ownership was about 60% highway 40% city…

The transmission range sensor went out in the transmission six months ago. It was a $430 repair. I kind of had a feeling then it might be a sign to move on from the vehicle.

The friend who suggested replacing the rod bearings has a hoist and would do the job with me. He owned an automotive repair shop at one point, and feels this could be viable fix. I am somewhat skeptical of this being a trustworthy repair for same reasons some of you have already mentioned.

Thanks for all the replies. You gave me a lot to think about.

A “knock” on startup on a 3/3 tha goes away after 3 seconds is due to the oil filter going dry because of a poor drain back valve. A real rod knock gets worse as the engine warms up and the oil thins. The 3.3 used to use 10w-30, I suspect the change was made so they could gain a fraction of a point in the EPA test.

My 2002 Chrysler minivan 3.3 was doing the tapping on startup/ I was using Fram or Mopar filters and due to a tip I read on a Mopar forum I changed to a Motorcraft filter and the startup noise went away.

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Not exactly, but it’s a classic car now, which was super-common in my younger days. I actually got this from a good customer of the company I work for. A former tenant left it at one of his rental properties. I inquired about the car, and convinced him to get an abandoned title for it versus just having a towing company haul it away. Since I have done so much quality work for this customer, and saved him many thousands of dollars, he did and I have a good title for this car.

I paid the costs of getting the title, which were about $300. The keys were in it, and with a new battery and some fuel, it started, but the engine knocked loudly. Since I figured it was going to need major repairs regardless, I drove it home rather than paying for a tow. When I ultimately disassembled the engine, it was full of oil sludge, which required copious amounts of carburetor cleaner to remove. I assume the owner drove this car for many years and never bothered to change the oil, which is very common among owners of cheap economy cars…hence why few of them survive past 10-15 years.

Good info. Here’s another data point: I generally use Motorcraft oil filters on my Ford 302 v8 truck, never been any knocking on start-up in 50 years. But there’s no-knocking on start up when I use a Fram oil filter either. I believe the common versions of Fram oil filters have the anti-drain function built into their design. I expect the NAPA filters do as well. Still it might make sense for OP to try a different brand of oil filter, Motorcraft would be my first choice, presuming they make one that fits the GC. Fram would be my second choice. Or maybe try a dealership oil filter.

As far as replacing the rod bearings, never done that job myself, but I’m guessing the pro’s here would remove the engine first, rather than attempting the job with the engine still installed. Just makes it a lot easier, and not overly difficult to remove an engine with typical shop equipment, esp if you’ve done it before. With a lift, with the engine installed, the job is probably unpleasant, but doable. Without a lift it would really be a chore.

Sorry you had that problem w/the transmission range sensor (TRS), but I doubt it is related to the oil pressure problem. That part just plumb wears out after a certain amount of shifting. TRS problems are the subject of quite a few posts here, various makes and models.

As a matter of fact, I’d decline the job outright

I just wouldn’t want to get in a situation where I took measurements, decided on what size bearings I needed and then the problem wasn’t fixed . . . or only bought a few weeks of relief . . . and then the customer comes back and says “you PROMISED me the bearings would fix the engine, but now I need a new engine anyways . . .”

Sometimes it’s best to just decline a job, imo

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Low oil pressure at idle is not a big problem. At speed, the amount of oil being pumped is far greater and there is probably enough pressure and volume to lubricate the engine’s internals. If not, be thinking about what to do in the unlikely event the engine seizes up.

Hmmm, pull the engine. A couple guys I knew did it in the driveway laying in the snow and a trouble light at night.

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As a professional mechanic, sure…but I am not a professional mechanic, and neither are most of the people here. As a DIYer, I don’t have to worry about covering the costs of running a business, making a profit, customer complaints, negative online reviews, etc.

The Fram and Mopar filter both hve anti drainback valves, the Motorcraft filter has a better one, made of Viton. A Mopar filter is the Chrysler brand.

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I would consider a 2007 van to be boarder line as to be “old”.

If this were my vehicle, I would remove the engine and inspect the crankshaft. Check and refinish the crankshaft if necessary or buy a long block.

However, if replacing a range sensor costs $400, maintaining and repairing an aging vehicle is not for you.

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I couldn’t agree more

Perhaps op would be happiest if they traded in vehicles as soon as they were paid off

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I like the idea of 20-50W oil and a filter with the check valve. Very cheap experiment, you might get weeks or a year or two out of it. But you now have the warning signs, be ready to replace the car.

Try adding a can of Restore to the oil. Might help, might get a few more miles out of the engine, low risk low cost

Restore is not an engine oil viscosity index improver.

Restore fills the scratches in cylinder walls to improve compression and reduce oil burning.

https://www.restoreusa.com/index.php

A total misapplication of a product.

Tester

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Oil Pressure is best when the vehicle is new as it wears ofcourse the pressure should decrease,
need to really check it out, may need to replace the oil pump?

Unlikely to help unless there was prior oil maintenance issue. . Oil pumps are generally constantly bathed in oil, uncommon failure items.

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Well you have never replaced an oil pump? They do wear down and when they do replacing them is a choice. Now the topic of oil choice should be made by the OEM recommends, before you tell me that my solution is the choice you should avoid, make your own treat mine as just another solution regardless if you personally do not like it!

I suspect a worn engine . . . not a worn oil pump

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Thicker oil will make the low oil pressure light stay off when the engine warms up. The reason it is coming is the oil gets thinner as it heats up.

I say go ahead with the rod bearing change. Likely the previous owner used 5W-20 and went way too long between oil changes. Everything else besides the rod bearings may still be in decent shape. How bad is the engine oil consumption? If this fixes the knocking, then at the next oil change take the pan off the transmission and change the fluid while you’re at it. Because the transmission could be the next thing to go.

Wouldn’t this happen when starting the engine on a cold winter day?

A lot of damage can happen during that time. 70k miles is one of the worst milages to buy a vehicle, because the engine has enough miles on it for it to be close to worn out from neglect, but not enough miles for the neglect to be noticable yet.

5W-20 should have not been used since this vehicle hit 100k miles!

This is a good example of what happens when thin oil like 5W-20 is used, and likely combined with infrequent oil changes. The oil breaks down and becomes 5 weight. 5 weight is so thin that it cannot lubricate the rod bearings. From air cooled engine experience, the first thing to go on an engine when the oil gets too thin is the rod bearings. Putting in SAE 40 instead of 30 in my salvaged lawn mower caused the somewhat noticable knock that it made when it warmed up to go away. It works fine now and doesn’t have abnormal oil consumption.

If someone may drive the vehicle 20k miles without changing the oil, then they should just put straight SAE 30 oil in it. It won’t break down in to a thinner oil, and it won’t produce as much sludge.