Rod knock/bearing replacement?

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stooks

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I've got a2008 toyota sienna, 205k, that developed what I was told was a rod knock. It was not ran with low/no oil. The sound is intermittent, particularly prominent with a mid range load on the engine. When the knocking was very loud the oil light flickered on the dash(oil was full) It is loud, but has been driven very little with the noise. A trusted mechanic friend told me that the engine needed to be replaced (he told me he was too busy to do it).

While hunting around for a cheap replacement motor; I came across videos and discussion of just replacing the rod bearings as a stopgap measure. I though it might be worth it to save $2k on the replacement. I got the upper and lower oil pan off tonight, and none of the rod ends are loose. They all have a limited amount of play side to side (maybe .005"), but are tight in up/down movement. The oil pickup tube in the pan was pretty gunked up on the bottom. Other then that the pan, and associated parts were surprisingly clean with that many miles on it.

Was this wrongly diagnosed? Are all the bearings bad? Any other ideas?
 
How about the main bearings? You really need to pull the bearing caps to see what they look like.


Is it an aluminum block? A bad belt tensioner can sound like rod knock on an aluminum block. This is common on the saturn s series. I once bought a great running saturn sl2 that the owner thought had rod knock. I knew better and bought it for $500. Replaced the belt tensioner and voila, no knocking sounds.
 
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"Rod Knock" is one of the more common failure modes of high mileage engines, but it's not the only one, or the only one to create load-dependent noises. Replacing crank bearings with the motor in the vehicle is often not a difficult or impossible job; you've already got the pan off so that part of the job is familiar to you already.

You can simulate the load by revving the engine in gear with brakes applied. BE CAREFUL, don't let whomever is operating the vehicle run you over. Same with the "remove plug wires" method of nailing down which cylinder is at fault, although it's probably best to just replace all main bearings at once if they prove to be the problem.

Other engine failures will require removal of the engine in most cases to repair (eg piston slap) so a full rebuild or reman replacement is probably in order at that point. Don't be afraid of buying a good used motor from a wrecker's; it will probably outlast the chassis you have at 200K Mi anyway. Only buy from salvage yards that offer a warranty (90 days is enough), and can provide you with the exact mileage of the donor engine. You should be able to find complete engines with less than half the miles as you have on your chassis.

$2K seems high to me for a working low mileage junkyard engine, and low for a remanufactured one. I paid $C 1300 ($US 988) for a motor + transmission, 43,000 Km [26,700 Miles] from a wrecker in Japan for my Mazda. That's overseas shipment, rail to Montreal where the seller is, and then truck freight back 2500 miles west to me included.

Japanese consumers generally retire their vehicles with low miles, based on model year age. The culture is different .... owning a car is a status symbol, but few urban residents can store the car in the city. So they take the train to work and the train out to the countryside where the car is stored for family outings on weekends. Toll roads with booths every 40 km and expensive tolls (think $20, not $2) make long drives expensive. Vehicles rarely are worn beyond 50,000 Km before they are sent to the recycler, and there is a surplus of good removed parts such as motors or transmissions. It's easier to import them into Canada than the US as I understand it, but far from impossible.
 
You should use Plasticgauge to measure bearing clearance, and also the the mains. That being said, I think you are on to the real cause, clogged pickup, which would explain the low oil pressure light.
 
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It is an aluminum block, but the belt tensioner would not explain the flickering oil light?

I haven't looked at the main bearings, but will try to check those as well.
 
It sound like a bad oil pump, stuck relief or clogged pickup or both may have been the initial cause, the engine looses pressure and you get a knock.
Some damage has probably already been done, an oil pressure test should have been do first. Remove all the caps main and rod one at a time and look for damage then post back. No point in getting all long winded about it till we know what you are dealing with.
 
He diagnosed it by having me put it in reverse, parking brake on, foot on the brake and slowly revving the engine. The knock appeared along with a flickering oil light.

My plan was/is to replace the rod bearings in the car, I will check the mains as well. Would they cause knock?

The $2k figure was roughly $1k for engine, and $1k for installation. It's hopefully a little high, but not massively from what I understand. Would rather plan on that and end up at $1600, then the other way around.
 
If the Plastigage measurements check out, it may just need the oil pickup replaced & a little thicker grade of oil, say 5 or 10W40, to get rid of the noise. As mentioned above, a lot of things can simulate a rod knock under load-I actually have the most luck revving an engine to a moderately high RPM, say 3000, and holding it there or slightly lowering the engine speed, in Park or Neutral (w/emergency/parking brake on). If there is a bad/loose rod bearing, you'll hear the telltale rattle.
 
Originally Posted By: stooks
He diagnosed it by having me put it in reverse, parking brake on, foot on the brake and slowly revving the engine. The knock appeared along with a flickering oil light.

My plan was/is to replace the rod bearings in the car, I will check the mains as well. Would they cause knock?

The $2k figure was roughly $1k for engine, and $1k for installation. It's hopefully a little high, but not massively from what I understand. Would rather plan on that and end up at $1600, then the other way around.
Mains usually are a deeper noise, like a thunk, rods are usually a "clank". A clogged oil pickup (generally accompanied by a sludged oil pan) can be enough to cause noises.
 
If you had noise at the same time as your flickering oil light, you've got damage. Period.

The cause is likely that clogged pick-up.

You can't tell rod clearance by hand. Plastigauge will tell you what it actually is.

If it were mine, since it's already apart, I would pull each bearing cap, rod and mains, and look for scoring on the journals. If they look OK, replace the bearings. All the lower end bearings, and then replace the oil pump and pickup.

If not, find a used engine.
 
Originally Posted By: tomcat27
You should use Plasticgauge to measure bearing clearance, and also the the mains. That being said, I think you are on to the real cause, clogged pickup, which would explain the low oil pressure light.


That and I was wondering about the oil pump . Depending on how it is made , now that you have the pan off , I would think about replacing it and the pickup / screen .

And then , visually inspect the rod bearings , first . Then the mains . As has been suggested .
 
We have done lots of bottom end rebuilds where we take out the crank and pistons, change the bearings and sometimes the wrist pins in the piston and the reassemble and the engines go on for hundreds of thousands of more miles.

Rod knock is a very distinct sound and a good mechanic can diagnose it from a mile away but can't tell what's causing it without properly dissembling the engine unless the bottom end is totally messed up with a ton of play in which case the noise should be something like a fork in a blender. Measurements are usually necessary to see what part is causing it unless the bearings are badly scored sort of thing.

Something that could also be causing the noise and it is similar to rod-knock in some cases but isn't common on Toyota's is the flywheel. A broken or loose flywheel can sound very similar to rod-knock in some cases. We have had this a handful of times on various makes/models over the years. My dad was actually given a Chrysler K-Car because the guy thought the bottom end of the engine was done and it turned out to be a fly-wheel. My dad drove it for 12 years!
grin2.gif


I would get a second opinion from another good mechanic. (look up reviews) and don't tell them you had it to another mechanic and don't tell them you think it's rod-knock. Just go in with "it's making a noise" and I'm not sure what it could be and see what they come back with. A good quality dealer is worth a visit as that secondary mechanic opinion.

Good luck
thumbsup2.gif
 
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Popped off all the caps, all 6 rod bearings are smooth as glass with no visible wear or damage. I have not checked the mains yet.

As I was spinning the crank, I noticed this spot that didn’t look right.
Zu1AXP7
 
Rotate the crank and look if there is anything contacting it in that area otherwise I would guess it was probably done when the crank was balanced.
Cranks are usually balanced by adding heavy metal slugs to add weight or metal removed of the counter weights with a lathe but if it was only a couple of grams heavy they may grind it in mass production.
 
I can neither see or feel anything rubbing. I suppose that is to balance the crank, because directly opposite that side is much bigger, since if that side hit something, the other side would definitely. There is no movement other then rotation
 
That's what I figured, a little grind is easier and less time consuming than trying to lathe off a few grams with a lathe, how do the mains look?
 
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