Ls3 water pump failure
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Ultimate Chevy LS3 Reliability Guide

Chandler Stark

Meet Chandler

Chandler is an automotive expert with over a decade of experience working on and modifying cars. A couple of his favorites were his heavily modded 2016 Subaru WRX and his current 2020 VW Golf GTI. He’s also a big fan of American Muscle and automotive history. Chandler’s passion and knowledge of the automotive industry help him deliver high-quality, insightful content to TuningPro readers.

Despite making such gaudy power numbers, the pushrod LS3 is also an extremely dependable engine. They are capable of taking a serious beating, both stock and modded, and can last for 100,000s of miles and many years. Read on to learn about GM LS3 reliability and common engine problems.

Chevy LS3 Reliability

Credit: David Kimble & Motor Trend

Overall, we consider both the LS3 and L99 engines to have above average reliability. In general, the LS and Vortec-series of V8 engines are solid and have the ability to last for many miles. Some people actually consider the LS3 to be the most reliable of the bunch. There were no problems with the valve train like the LS7, and buyers had lots of success with it right out of the box. For some, LS3 reliability is the engine’s greatest strength. 

Now that it has been around for more than 15 years, it’s clear that GM/Chevy got it right with the LS3. Many people have taken these well past 150,000 miles without serious issues, and they even stand up well when modded. Despite their use in such high performance cars like the Camaro SS, Chevrolet SS, and Corvette Z51/Grand Sport, the LS3 has shown that it is more than capable of lasting a long time. 

This also includes its cousin the L99. While not as powerful, and prone to more issues due to the AFM (which we’ll get into below), it is still a very solid and sturdy power plant. Both the LS3 and L99 are more than capable of being daily drivers for many years, even with spirited driving and occasional track use. 

However, no engine is ever perfect, and LS3/L99 owners have experienced a few issues over the years. We would not call any of these problems endemic, but they have seemed to affect more than a few LS3 owners. While LS3 reliability should not be called into question, it’s still important to be aware of these things.

4 Most Common LS3 Engine Problems

  • Water Pump Failure
  • Bent Pushrods
  • Oil Leaks
  • L99 AFM Lifter Problems

Throughout the rest of this guide, we discuss the above LS3 engine problems in greater depth. Again, it’s important to point out that it’s a highly reliable engine. These are simply some of the most common areas for issues when things do go wrong. That doesn’t mean every engine will run into these problems, though.

1) Water Pump Failure

Ls3 water pump failure
Ls3 Water Pump Failure (Image: GM)

The first issue we’ll talk about with the LS3 has to do with water pump failure. Water pumps serve relatively simple but very important purposes on engines, and they have a lot to do with determining LS3 reliability. Despite their importance, the LS-series of engines has been plagued with faulty water pumps, and they’re not the only ones. BMW’s N52 and N54 are notorious for having catastrophic failures due to faulty water pumps. 

The purpose of the water pump is to circulate coolant throughout the engine and radiator. Coolant is what keeps the engine block from overheating and it circulates the block through coolant passages. However, after circulating through the engine for a few minutes, the coolant becomes hot and needs to release its heat.

In order to do this, the water pump pushes the coolant into the radiator, where it exchanges the heat into the air. Then, the now colder coolant is recirculated through the engine block, where it can help cool it down until it takes on too much heat, and the process repeats. The thermostat is responsible for controlling the engine’s temperature.

Without a water pump, the coolant will stay in the engine block, where it will eventually take on too much heat and will be unable to stop the block from overheating. This can cause catastrophic engine damage, in the form of detonation, pre-ignition, or a melted block or internals. Water pumps do not show a lot of warning before they let go, and they can happen at any time. Some work fine for 200,000+ miles while others crap out at 50,000. It’s really a crapshoot. 

Water Pump Failure Symptoms

  • Engine overheating
  • Coolant leaks under vehicle
  • Low coolant levels
  • Low coolant level light
  • Squealing noise from water pump
  • Poor engine performance

The most obvious signs that your water pump is going out is going to be coolant leaking and engine overheating. If the coolant can’t circulate it will heat up very quickly, within a few minutes of operation, and so will the engine. You’ll notice the temperature gauge on the dashboard start to spike, followed potentially by a low coolant level light. You also might start to notice small coolant leaks under your car after parking it for a length of time. 

You might also hear a squealing noise coming from the water pump in the engine bay if it starts to go out. This is less likely, and usually indicates an immediate problem, but it does happen. In addition, you might notice a decrease in performance that could indicate a problem. If the engine oil and block gets too hot it can cause detonation, which will severely hurt engine performance and can cause engine failure itself. 

2) Bent Pushrods

Next up is LS3 pushrod failure. This is far less common than water pump failure, but has been an issue for some drivers. Many people praise the LS3 for its old school and more simplistic pushrod actuated, overhead valve (OHV) design, but it’s not always the best. Pushrod engines work by using a single camshaft that is located in the engine block. Valve lifters sit on the camshaft lobes, and in turn pushrods sit on the valve lifters. 

When the camshaft rotates, the lobes push up on the valve lifters, which then push on the pushrods. The pushrods then actuate the rocker arms, which push down on the valve stems to open and allow air into or out of the engine. If the pushrod gets bent, it will be unable to properly actuate the rocker arms. This will affect the valve’s ability to take in or allow for air to exit. 

The most common cause of bent pushrods is from mechanically over-revving the engine. The LS3 has a 6,600 rpm redline, but some people like to remove the limiter or raise it. In addition, a miss shift can also cause an over-rev. Unfortunately, the LS3 valve train does not take kindly to pushing past 6,600 rpm. The number one problems are floating valves and bent pushrods. 

Bent Pushrod Symptoms

  • Engine Ticking Noise from Valve Train
  • Cylinder Misfiring
  • Check Engine Light
  • Poor or Unstable Idle
  • Poor Engine Performance
  • Poor Fuel Economy

Depending on how severely and how many are bent, you may or may not notice a bent pushrod right away. The most obvious symptoms are going to be a ticking noise from the valve train, cylinder misfires, poor or unsteady idling, poor engine performance, and severely reduced fuel economy. You may also get a check engine light related to the valve train. 

Replacing LS3 Pushrods

If you do find yourself with bent pushrods, we highly recommend you get them fixed immediately. Bent pushrods can cause serious valve train problems, which can in turn cause problems with combustion. This can lead to catastrophic engine failure or blown internals. 

Replacing pushrods is relatively easy, as OHV engines are much easier than overhead camshaft engines. They are also relatively inexpensive for a set of stock replacements. If you plan on modifying the LS3, or if you already have, performance pushrods that are strengthened beyond stock might also be a worthwhile upgrade while you have the valve train apart. Either way, get it done immediately if you suspect a problem. 

3) Oil Leaks

Another somewhat common issue among LS3 owners are oil leaks. OIl leaks happen on pretty much every engine, especially those with higher mileage, and they are common on LS-series engines. For the LS3, the most common spots are leaks are usually the oil pan, oil cooler gasket, and valve cover gaskets. They can spring leaks at any time, and finding the source of an LS3 leak can be very frustrating.

LS3 Oil Leak Fixes

LS3 oil leaks can be impossible sometimes to track down, and the only way to fix them is to find the leak (usually a gasket) and plug it. If you notice a leak, you’ll want to get under the car and try to find the source. Sometimes, you might need to wipe everything clean and come back in a few hours or after a drive to see if you can spot fresh oil. 

4) L99 AFM Lifter Problems

Our next problem is only applicable to the L99 variant and does not really affect LS3 reliability. However, it is still an important problem to talk about. As we mentioned above, Active Fuel Management (AFM) is a cylinder deactivation technology. At certain times when the engine is operating a lower-loads, the ECU will deactivate four of the eight cylinders. This improves fuel economy and emissions, and is a feature on many Vortec and truck engines. 

It’s not entirely clear why, but many people attribute AFM to oil consumption and valve lifter failure. Previously, on our sister website ChevyTrucks we looked at AFM and how to delete or disable it. Disabling AFM simply stops the ECU from engaging cylinder deactivation, and involves either ECU tuning or purchasing a disabling device. Deleting AFM involves swapping out various valve train components with non-AFM pieces. 

For most people we recommend disabling AFM, as it can stop potential issues from happening and is also reversible. Check out our guide for information on both deleting and disabling. 

Importantly, the L99 inside the 2010–2011 Camaro SS was subject to a NHTSA Technical Service Bulletin regarding lifter failure. This means that Chevrolet knows that there was at least some issue with AFM and lifters on early L99s, though they claim the problem was rectified from 2012 on. 

LS3 Reliability FAQ

How long will a LS3 engine last?

The LS3 is a very reliable engine that is capable of lasting many years and well over 150,000 miles. Some people consider the LS3 the most reliable of all the LS and Vortec-series of GM engines.

Is the LS3 a reliable engine?

The LS3 is a very reliable engine that is capable of lasting many years and well over 150,000 miles. Some people consider the LS3 the most reliable of all the LS and Vortec-series of GM engines.

What is the life expectancy of an LS3 engine?

The LS3 is a very reliable engine that is capable of lasting many years and well over 150,000 miles. Some people consider the LS3 the most reliable of all the LS and Vortec-series of GM engines.

What are common LS3 engine problems?

The most common LS3 engine problems are water pump failure, bent pushrods, oil leaks, and AFM lifter failure on the L99.

Is the L99 engine reliable?

The L99 is a very reliable engine that is capable of lasting many years and well over 150,000 miles. It is based on the LS3, one of the most reliable motors ever built.

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