Toyota Avalon Sludge - Pull engine or leave it in?

Last weekend I pulled off the valve covers on my '99 Toyota Avalon with the intention of replacing the leaking valve cover gaskets. I found a load of caked on sludge and crud. This is my fault for using conventional oil and going too long between changes, so I’m not looking for additional flames here.

My current plan is to pull the heads and the oil pans and clean them out real well, then switch to synthetic oil and be more diligent about oil changes.

So, here’s my question: Is it better to pull the engine out of the car to do this work, or better just to work in place.?

Things in favor of pulling the engine: It’s cold in Virginia in December/January and weekend days are short. I’d be working in the driveway outside if I leave the engine in. If I pulled the engine, I could bring it in through the basement door and work in relative comfort and take advantage of the evenings after work. I wouldn’t have to worry about rain & snow. Also, I might be able to do some additional cleaning and fixes along the way (piston rings, etc.).

Things in favor of leaving the engine in: You don’t have to pull the engine out and put it back in again.

The car has 130,000 mile on it and the body is in very good shape. I don’t expect to be able to buy a nicer replacement car for at least five years or so (with kids in college). I do mostly around-town driving.

Any thoughts? Words of Wisdom?


I wouldn’t pull the heads…

Drop the pan…YES…Pull the valve covers and clean as much sludge you can.

Then start using synthetic…and I’d even consider something like Rislone every oil change.

The car is 13 years old. Pulling the heads is an awful lot of work for a vehicle that old.

After the discovery of "sludge’ you need to consider the NOW overall health of that nice engine Toyota made for you… Problem is…it WAS nice…when the oil was neglected it became un-nice. The real question here is…IS it worth it to try and clean out and or revive this engine? The sludge you see is simply a byproduct of abuse and neglect…this neglect has already taken its toll on the friction surfaces in the engine.

Now if it still runs fine…and there is no rod knock or general “Looseness” to the engine…Just leave it in…and leave it BE… You can remedy the sludge with subsequent oil changes and flushes… The flushes are what worry me…If you physically go in to the valve covers and clean out what you see…the bottom end will most likely NOT be the same as the upper valve cover area…the bottom end will be rather clean actually…It is only when you start to flush the crap from the top…into the bottom where you run into trouble.

Back in the old days this “sludge” actually held the motor together…and when you washed away all this Over-tolerance filling material in the engine did you finally see the actual wear that had been incurred…In the old days…sometimes a motor flush was a motor death.

If I were you…I would clean out the valve cover areas to remove the hardened oil and chunks…making sure they dont clog an oil return port etc… Then just put the covers back on and go with new oil…MAYBE a flush…but new oil and then repeated ON TIME or earlier Oil changes…

There is no advantage to tearing the engine really far down…or removing it. You wont buy yourself much.


I’m with Mike and Honda BB on this one. You can remove a ton of the “load of caked-on sludge and crud” by removing the valve cover(s) and cleaning it (whatever you can get at on the head) thoroughly . . . then doing the same to the oil pan and pickup tube & screen. After that . . . I’d do an oil and filter change at 500 miles . . . another at 1000 miles, using Dino for those two changes, for what? . . . $40 or so? Then I’d change after another 1000 to synthetic and do normal changes every 3000. Let the Dino carry away the crud you didn’t get to the filters you’ve changed, and maybe by the 3rd change you’ll have a pretty clean engine. Maybe. Good luck! Rocketman

Don’t pull the engine; just change oil frequently (1500 miles) and use a can of Rislone with every oil change. After a year you will have most of the sludge out. In view of the age of the vehicle I would not go to a major expense. As other have said, scraping off as much of the visible stuff as possible and opening the oil galleries is the most I would do.

You don’t need synthetic to avoid sludge!!

Here’s what I do to clean sludge from engines.


That would be the BEST way to remove the sludge…Just have to justify is it worth it on a 13yo car.

I’ve NEVER seen an engine that sludged up. And I tore down some sludged engines back in the 70’s when unleaded gas was introduced and some oils couldn’t handle the increased temps the engines were producing.

Yes. I read the Qslim write-up. That’s what inspired me to pull the heads. So far, the heads are still on, but I’m getting pretty close to pulling them.

As to whether it’s worth it for a 13 year old car - it’s still running well and I don’t (and won’t for a while) have the money to replace it.

If it takes some labor to wash away my sins (and, yes, the sins are mine), then it’s probably worth it. The car still looks good and runs well – except for, you know, the oil light came on right after I cleaned under the front valve cover - which means the oil screen is now completely clogged. Hence the plan for cleaning the oil pans & screen. I was pretty careful when I cleaned under the front valve cover, but there’s no stopping a little bit of gunk heading down to the oil pan.

You would be making a mistake by going in the piston rings. That can open up a can of worms if it’s not done correctly. With the mileage and sludge the cylinder bores could be egged and tapered so a proper job would mean boring the engine block for oversize pistons.
This means removing the connecting rods and you will probably find the bearings are worn through the overlays and this leads to checking the crankshaft journals for egg, taper, and so on; meaning a possible reground crankshaft.

I’m not a big fan of trying to desludge an engine. The most I would do is drop the oil pan and clean it along with cleaning the oil pump pickup screen. I’d scrape as much as possible off of the valve train, make sure the oil drain holes in the cylinder heads are clear, and maybe give it a few oil changes after running a comparatively length of time.

With the oil pan off you might remove one of the crankshaft main bearing caps (fartherest from the oil pump) and see if the bearing is worn into the copper and/or scored up badly. If it is then you might consider throwing a new set of rod and main bearings in and calling it good.
Any deeper than this, in my opinion, starts pointing towards a complete engine overhaul and that will be $ even if you did all of the work yourself.

I agree with those who say not to pull the heads. If you have the equipment and its easier to pull the engine than it is to pull the pan, then pull the engine, but leave the heads on.

Make sure that the drain holes from the head to the pan do not get blocked up. Flush out those holes real good, then clean out the pan and pickup screen.

If you do pull the engine, I would suggest that you look at the timing belt/chain and the front oil seals, crank and cams. I would not do that unless you decide to pull the engine, those things can wait for better weather and when they are due.

Toyota actually had a poor design of the PCV that caused excess deposits(sludge) especially with extended oil changes.

Its a known problem of your vintage Toyota V6.

My mom was a victim but Toyota fixed the motor well out of warranty.

If you decide to remove the engine and if you are going to remove the crankshaft pulley bolt to service the timing belt/water pump or remove the heads, I recommend cracking the bolt loose while the engine is still in the car. You will have much more leverage that way and you will need it.

Put the valve covers back on and drive on…Now is not the time to start worrying about it…Rislone and 2000 mile oil changes will take care of the problem without causing many new ones…


LOL at Here’s what I do to clean sludge from engines.

The last pic says he is refilling the oil, yet the funnel is in the water outlet. And the oil cap isn’t even removed. LOL

I think there’s a consensus here. I’ll clean out the gunk that’s visible under the valve covers (feels like being a dental hygienist), and drop the oil pan to clean the intake screen. Maybe I’ll revisit it in the summer.

Thanks for all your suggestions!