Toyota is a company known for their ability to build fantastic engines, but every once in a while, even they put out a powertrain that isn’t up to snuff. The 2AZ-FE is widely considered to be one of those engines. While it isn’t a bad engine per se, it is plagued with some pretty serious issues that can add up to some pretty expensive repairs down the line. Those issues include heavy oil consumption, stripped cylinder head bolts, and cooling system problems. Let’s take a look at those issues in more detail.
One of the most talked about 2AZ-FE engine problems is its tendency to burn a lot of oil. When I say a lot, I truly mean it. In some cases, they can burn as much as a quart every 600 miles, which is ridiculous when you consider that 11 quarts would have to be added to the engine between oil changes on average. While not affecting every engine, the issue affected the engines found in 2007-2009 Camrys and 2006-2009 RAV4s the most.
The oil consumption issue boils down to the piston head design on late model 2AZs. The oil return holes located behind the oil control piston rings get clogged over time, preventing excess oil from returning to the crankcase. With no place for the oil to go, it ends up burning up in the combustion chamber. Unfortunately, oil consumption tends to get really bad around the 45-50,000-mile mark, which is extremely early for a Toyota engine.
2AZ-FE oil consumption issues became so widespread and serious that Toyota eventually issued a technical service bulletin for the problem. The bulletin outlined an inspection procedure to see if the vehicle was eligible for replacement parts under another technical service bulletin. Toyota redesigned the piston and piston rings with larger oil return holes which significantly lessened oil consumption.
Oil Consumption Symptoms
- Blue or white smoke from the exhaust
- Oil level light illuminating
- Low oil level on dipstick
- No visible oil leaks despite decreasing oil level
Since the 2AZ burns oil at such a fast rate, it is really important to check your oil level frequently. Like every time you stop for gas, frequently. While the low oil light will likely alert you to the issue, it is best to not let your oil level get that low to begin with.
Oil Consumption Fixes
Since so many 2AZ-FE owners have experienced excessive oil consumption, many of them have tried a ton of things to reduce the severity of the problem. Ultimately, the only true fix is to have the old pistons replaced with the revised ones provided by Toyota, but since all affected models are outside of the extended powertrain warranty window at this point, that is an expensive and time-consuming option for most people.
Outside of replacing the pistons, other owners have tried some less invasive ways of solving the problem. Changing the type of oil you use can help a bit. Toyota recommends 5W30 synthetic oil in early (2000-2007) engines and 0W20 in late model (2007-2018) engines, however, they don’t specify which exact oil to use. Most owners recommend using an oil with a low NOACK level. Oils with a low NOACK level are less prone to evaporate which can help the engine retain more oil. Oils like Amsoil, Redline, and Mobil 1 tend to have the lowest NOACK levels.
In addition to trying new oils, some 2AZ-FE owners also say that other oil treatments can help the situation a little bit, but that they aren’t a permanent fix. There are conflicting reports that Sea Foam can help reduce oil sludge in the piston rings, reducing oil consumption significantly. Others say that it’s truly just snake oil. Ultimately, replacing the pistons with the revised parts is truly the only way to stop oil consumption for good.
Stripped Head Bolts
Stripped head bolts are another very common problem with the 2AZ-FE. It’s a pretty serious issue, as it can lead to engine-killing issues like coolant intrusion and low cylinder compression. The 2.4L inline-4 features an aluminum cylinder head and an aluminum block to save weight, which is pretty common across the industry. That isn’t an inherent issue, but it is a problem if the engine overheats. In that case, the aluminum cylinder head expands more than the steel head bolts expand.
As the cylinder head continues to balloon, it puts a ton of strain on the head bolts which have the job of securing the head to the block. Since the head bolts are screwed directly into the aluminum block and aluminum is such a soft metal, the excess pressure causes the steel head bolts to tear through the threading in the block. At that point, the bolts can’t keep the head secured to the block, allowing leakage between cylinders. It also allows coolant to leak out of the cooling jackets.
The 2AZ’s bad head bolt design is extra unfortunate since the engine also has cooling system issues which can easily cause it to overheat. It makes purchasing a 5th Gen Camry (or any other 2002-2006 2AZ-FE-equipped Toyota) a bit of a crap shoot, as there is a very real chance of the head bolts stripping in the future if the engine ever overheated in the past. However, it is possible to check VIN-verified part websites to see if the car has a problem block or not.
Problem Block Part Number: 410-09050
Revised Block Part Number: EG015-07
Stripped Head Bolts Symptoms
- Finger-tight or looser head bolts
- Coolant leaks from the rear of the engine
- Low compression on one or multiple cylinders
- Engine overheating
- Wet intake manifold insulating foam
Stripped Head Bolts Fixes
Luckily, there are a couple of go-to fixes if you do run into stripped head bolt issues on your 2AZ-FE. While there are solutions, they are pretty in-depth and require the removal of the cylinder head in order to complete. If you aren’t too handy with engine repairs, leave it to the professionals.
One of the most common fixes is to install steel thread inserts into the short block. There are a few reputable kits on the market for repairing stripped 2AZ-FE head bolts including Time-Serts and NS300L Cylinder Head Bolt Thread Repair System kits. The process of installing them is relatively straightforward. You’ll need to drill the existing bolt holes to a larger size, tap the larger holes to accept the inserts, thread the inserts into the tapped holes, and use some kind of bonding agent to keep the inserts from spinning when you screw new head bolts in.
Outside of installing tread inserts, the only other true solution is to replace the short block entirely. Obviously, that isn’t ideal as that can get very expensive very fast. But, if you want to drop the cash, it’s an option. Regardless, it is important to fix the stripped head bolt issue as soon as you notice it to avoid catastrophic engine problems later down the line.
Cooling System Issues
The 2AZ-FE is also notorious for having all kinds of strange and annoying cooling system issues. Since there are so many common coolant leak locations on the engine, it can be hard to pinpoint the exact cause of coolant loss. Piggybacking off of the last section, many 2AZ owners experience coolant leaking out of the rear of the cylinder head due to loose head bolts, which is often a hard leak location for people to identify.
Water pump issues are also really common on the 2.4L I4, being a very hit-or-miss part. While some Camry, RAV4, and Scion owners have made it upwards of 150,000 miles on the original water pump, some have had their water pump fail as early as 24,000 miles. The most common cause of failure is actually the water pump belt either snapping or falling off, causing the engine to overheat rapidly. If coolant leaks past the internal seals and reaches the bearing, it can cause the water pumps to seize.
The rest of the cooling system is pretty par for the course as far as most vehicles are concerned. Most are old engines at this point, so normal cooling system wear and tear is to be inspected. Coolant hoses, the thermostat, the clutch fan, and the radiator should all be inspected frequently and replaced appropriately. It is especially important to stay on top of cooling system maintenance on the 2AZ-FE compared to other engines due to the other major problems, like stripped head bolts, that can occur if the engine overheats.
Faulty Cooling System Symptoms
- Visible coolant leaks
- Engine overheating
- Engine taking a long time to reach operating temperature
- Low coolant light
Cooling System Fixes
Ultimately, cooling system repairs are common service items on every engine out there. The consequences of cooling system issues on the 2AZ-FE are just more extreme than many other engines due to the head bolt issue. There isn’t a catch-all solution to bulletproof the cooling system. But, it is important to know about the risks that overheating has for this engine and stay extra vigilant on the gas gauge in case something does go wrong with the cooling system.
The water pump is unquestionably the most troublesome component in the entire cooling circuit. While there are plenty of reports of them seizing or functioning incorrectly at less-than-optimal mileages, most of them typically make it to around 100,000 miles, which is when they should be replaced regardless. While there are some cheaper aftermarket water pump options, it’s best to stick with the OEM part. If you’re competent with a wrench, you can typically DIY a water pump replacement in around 3 hours without needing any specialty tools.
The 2AZ-FE is a Good Engine With A Bad Side
Compared with some other Toyota engines that have built their stellar reputation as an engine manufacturer, the 2AZ-FE isn’t exactly at the top of the heap. It’s not a bad engine either, though. It is a torquey engine for a little 4-banger and has plenty of get-up-and-go for most Camry, RAV4, Matrix, and Scion owners. Some owners have learned to adapt to the engine’s issues and swear by its dependability if maintenance is up to date and the oil is topped off.
It is hard to look past some of the more serious issues though. Oil consumption is a serious issue on these engines and can end up costing you serious money from having to put a quart in every 600 miles. It’s even harder to swallow since there isn’t an easy fix due to it being a design issue with the pistons themselves. It is an issue that nearly every 2AZ-FE owner faces and there isn’t much you can do about it without forking out an arm and a leg.
Cooling system issues and head bolt stripping go hand in hand. If a cooling system component fails, like the notoriously troublesome water pumps, the engine can overheat rapidly, leading to stripped head bolts. While someone with the right mechanical know-how can fix that issue relatively inexpensively, retapping the block isn’t an easy job for beginners.
The 2AZ is a solidly performing engine overall with a few notable drawbacks. As long as you make sure that it doesn’t overheat or run out of oil, they can last hundreds of thousands of miles. If you want to learn more about it, take a look at our Toyota 2AZ-FE Engine Guide for more information about specs and details.