I read some of the earlier threads regarding this problem and thought the following might be helpful to those who have the sludge. My friend just sold his 99 after battling the sludge for over six months.
Q: I have heard about some Camry engines having problems with sludge build-up. I was wondering if my car is likely to have that problem, and what I can do to prevent it. I have read that toyota claims it is just due to people not doing regular oil changes. If my year is affected by this problem, will doing these regular oil changes prevent it? Or is the problem almost inevitable?
A: In February 02 Toyota finally acknowledged the condition, without taking real blame for any engineering problems, and started to correct the affected engines. They had some conditions that had to be met but their Special Policy Adjustment was a good start. They finally showed their true corporate stance on the unfortunate problem. They have broadened the scope of the coverage, within the years and models affected.
In April 2002, Toyota said it has made a running production change to its widely used 3.0-liter V-6 engine that will improve circulation by enabling oil to drain faster into the sump - an apparent acknowledgement that engine design has been at least part of the problem.
Second, Toyota said it will pay for sludge-related repairs for eight years from the date of purchase for all 1997-2002 Toyota and Lexus vehicles with the 3.0-liter IMZ-FE V-6 engine and all 1997-2001 Toyota vehicles with the now discontinued 5S-FE 2.2-liter four-cylinder engine.
Toyota's new policy is a dramatic change from a so-called Special Policy Adjustment begun in February. Amid increasing criticism for refusing to deal with the problem, Toyota notified 3.3 million owners of the affected engines that sludge-related repairs would be covered for one year, as long as they proved the oil had been changed at least once in the previous year.
It insisted then - as it does with the new policy - that owner negligence is the cause of the problem.
In contrast to the February offer, Toyota's new policy:
Has no mileage limitation.
Covers owners who buy used vehicles.
Reimburses drivers who already have paid for repairs
Includes payments for tow trucks, rental cars and other incidental expenses resulting from engines that fill with sludge. This seems affect mostly Avalon, Camry, Sienna, Highlander, Celica and most Lexus 300/RX series models with the model years after 1997 thru 2001/2002. Apparently, Toyota made a change in the engine design that actually contributed to the problem.
My biggest question is do I qualify? Here are the guidelines Toyota is using to establish the engines that are prone to having the sludge (gel) condition:
2.2 L I4
Camry Produced 8/96 - 7/01
Celica Produced 8/96 - 4/99
Corolla Produced 1998
Solara Produced 6/98 - 5/01
3.0 L V6
Camry Produced 8/96 - 7/02
Avalon Produced 7/96 - 5/02
Highlander Produced 11/00 - 7/02
Lexus ES300 Produced 8/98 - 7/02
Lexus RX300 Produced 1/98 - 7/02
Sienna Produced 7/97 - 5/02
Solara Produced 6/98 - 5/02
If you look at the vehicle identification label on the left door or left door post you can find the date of manufacture. It normally is one of the first things you can see on the upper left of the label (example 7/98 means it was made July, 1998).
The actual cause of the problem is an inability of the engine's crankcase ventilation system (PCV) to move the normal gases from the engine (fuel from blow-by, and water from combustion). When these gases stay longer in an hot engine it allows deposits to form on the metal parts of the engine. When enough deposits are present "Sludge" is formed.
Another contributor may be reduction of the size of cooling passages to the cylinder heads in those engines in order to increase combustion temperatures for more of a complete burn to reduce exhaust emissions. Excessive heat makes oil more susceptible to sludge. Cylinder-head temperatures as high as 260 degrees have been measured in those engines - 30 degrees higher than in earlier models.
The problem is magnified by short driving distances so that the engine oil never gets really hot, infrequent oil changes, or mechanical malfunctions. Using synthetic-based oil will also help minimize sludge formation since synthetic lubes are much less prone to oxidation than dino oils. Changing the oil more frequently will also help minimize sludge. There are alot of opinions on how often to change oil, but 3K miles for dino oil and 5K for synthetic oils are conservative and should be fine for most any engine (YMMV).
WHAT IS SLUDGE?
There are different "types" of sludge, they are of different appearance ranging from light brown to opaque black, they range from semi-liquid to solid, and they can be formed by different chemical reactions.
Since any sludge is formed primarily from the engine oil, the oil itself appears to be at fault. Actually the oil is the victim of mechanical and chemical attack.
The formation of sludge is a very complex interaction of components which include mechanical and thermal stress and multitude of chemical reactions.
Although there are thousands of documented engine failures in the field, not a single research chemist has to date succeeded to create a "synthetic" sludge under controlled laboratory conditions. The real life conditions are therefore so complex as to be virtually impossible to duplicate in laboratory, yet hundreds of engines all over the world fail daily due to sludge formation.
While some engine types are more prone to sludge formation, the fact is that only very small proportion of the "affected" engines actually fail in service.
Sludge in gasoline engines is usually a black emulsion of water and other combustion by-products, and oil formed primarily during low-temperature engine operation. Sludge is typically soft, but can polymerize to very hard substance. It plugs oil lines and screens, and accelerates wear of engine parts. Sludge deposits can be controlled with a dispersant additive that keeps the sludge constituents finely suspended in the oil.
"Black Sludge" is defined as thick to solid material with low water content, of dark color, light oil insolubles, and typically found in rocker cover, cylinder head, timing chain cover, oil sump, oil pump screen, and oil rings in variable quantities.
Sludge in diesel engines, is soot combined with other combustion by-products which can thicken the oil to gel like sludge. This sludge is typically soft, but can also polymerize to very hard substance. It plugs oil filters, oil lines and screens, and accelerates wear of engine parts.
More discussion on sludge formation:
How to prevent sludge:
What can I do since I have sludge?