Hello Subaru Driver,

Thank you for choosing Subiesmith to be the shop to replace your head gaskets. Before we begin, we want to go over some information you should be aware of. We are about to perform a very involved procedure on your vehicle. As with any complex procedure, there is always a possibility that complications may arise during or after service. We want to prepare you for the more common of these possibilities.

Rod Knock

What is it?

A rod knock is the sound that results when the bearing at the connecting rod attaches and the crankshaft comes loose. When the bearing comes loose, the connecting rod and crankshaft can rattle against one another. This will result in a repetitive “knocking” sound that becomes more rapid as engine rpm increases. Although, the sound can manifest in other ways as well.

What causes it?

The primary cause of rod knock is running the engine low on oil. High engine RPMs and normal wear and tear can contribute as well. If the engine ran low on oil before the leak was fixed, there is a chance that the damage that leads to a rod knock may have already started developing. When we take the engine out to replace the head gaskets, we drain all of the oil out of it. This necessary process can accelerate the connecting rod bearings failing if the process was already started. No part of the standard head gasket service will cause this failure.

Unfortunately, there is no way to tell if the engine has the beginning of a rod knock failure before the sound presents. The only way to visually inspect for this would be to completely disassemble the short block, which would add several thousand dollars to the repair. Without symptoms present, there is no justification to perform that procedure, with its high cost, as preventative.

If the engine ran low on oil, the odds of this failure go up significantly.

How common is it?

We see about one out of twenty-five engines develop a rod knock within 10,000 miles of a head gasket service. Sometimes it can happen right after service, sometimes it can take several thousand miles. If the engine has run low on oil, the odds of this failure go up significantly.

How do we fix it?

The fix for this failure is to replace or rebuild the short block. The short block is the portion of the engine that houses the crankshaft and pistons. This can be very expensive, as well as very time consuming to access. The exact price and timeframe will vary by engine and replacement part availability.

If the short block does fail within the warranty period on the head gaskets, we will help with the cost. There are two elements to the short block replacement; the short block itself and the labor and parts kit to replace it. You will be responsible for the full cost of the replacement short block, but the parts kit and labor needed to install the short block will be covered on a prorated scale based on mileage since the original head gasket service. If your short block fails within the first 1,000 miles of the warranty, we will cover 100% of the parts kit and labor. After the first 1,000 miles, the amount we discount off will be equal to the percentage of the 12,000 mile warranty that remains. Once the warranty has expired, by mileage or time, there will be no discount toward a short block replacement.

Warped Block Surfaces

What is it?

In order for the new head gaskets to seal properly, the machined engine surfaces that mate to the head gaskets must be perfectly flat. We have a specified maximum variation in that surface of .0015” from one corner to the other. There are two surfaces that mate to the head gasket, the cylinder head decks surfaces and the short block deck surfaces. Warpage in the cylinder head decks is very common and an easy fix. That service is already included in the price of the head gaskets. Correcting warpage of the short block decks is much more complicated.

What causes it?

The primary cause of warped short block decks is severe engine overheating. We do see this happen from time to time without a severe overheating condition. It is also possible that a previously done head gasket repair where the prior shop did not properly clean these deck surfaces can cause the surface variation to be in the decks. If the engine did not overheat, the odds of this failure are very low.

How common is it?

We see about one out of fifty engines with short block deck surfaces that are warped beyond specification. If the engine severely overheated, the odds of this failure go up significantly.

How do we fix it?

We have two options:

  1. Apply a spray on coating to the head gasket that may assist in sealing the head gasket. This fix doesn’t add any additional cost to the repair. This is only an option if the deck surfaces are out of spec by a small amount. This method will void the warranty on the head gaskets, as this is not considered to be a “proper” repair. We cannot guarantee this will solve the leak.
  2. Disassemble the short block so the short block deck surfaces can be resurfaced by a machine shop. This will add a significant cost to the repair but will maintain the warranty. This is effectively a rebuild or recondition of the short block.

Oil Consumption

What is it?

There are two ways that oil can leave an engine; it can leak out externally or it can burn with the air/fuel mixture internally. This is specifically referring to internal oil loss. We know you have oil consumption if the engine oil level declines, but none of the missing oil is leaking out of the engine. According to Subaru, up to one quart of oil consumption every 1,000 miles is normal.

What causes it?

The most common cause of oil consumption is having run an engine with a low oil level. The lack of lubrication will cause scoring on the cylinder walls, which will result in some of the oil sneaking past the piston rings. But even if the engine never ran low on oil, normal wear and tear can cause this. Sometimes, major engine repairs can accelerate the rate of consumption.

How common is it?

Most Subaru’s with more than 100k miles will experience some form of oil consumption. Severe oil consumption, or more than a quart every 1,000 miles, is rare. We see about one out of fifty engines with severe oil consumption. If the engine ran low on oil, the odds of this failure go up significantly.

How do we fix it?

The easiest and most economical way to address this issue is to check and top off the engine oil on a regular basis. We understand that this is not always convenient. There are also oil additives that can help slow the process.

The full solution to this issue is to rebuild the short block. This option will cost thousands of dollars. Drivers very rarely choose to go this route due to the high cost.

Spun Camshaft Bearings

What is it?

A spun camshaft bearing is damage to the precision machined surfaces that the camshaft rotates on. These smooth surfaces become rough and scored.

What causes it?

The rotating camshaft is held away from the housing it sits in by a very thin layer of pressurized oil. If there is debris in the oil, or if the oil pressure drops from a lack of oil in the engine, these smooth, precision machined surfaces will start to rub on each other. This will make them rough and they will start to bind up on each other. They will eventually seize up, causing catastrophic engine failure.

How common is it?

This is not a very common failure. We see this happen on about one out of seventy-five engines. If the engine ran low on oil, the odds of this failure go up significantly. We may not have the opportunity to inspect for this damage unless we receive authorization to remove the camshafts. This is not a default part of the head gasket replacement on some engines.

How do we fix it?

If the damage is minor, we may be able to polish the bearing surfaces smooth again. If the damage is severe, we will need to replace the damaged cylinder head. The cost for that will vary depending on part availability.

Parts Unsafe to Reinstall

What is it?

We may get your engine apart and find that parts we did not plan on replacing will need to be replaced. If reinstalling the faulty parts will create a dangerous situation, we may be required to replace these so we can continue with reinstalling your engine.

What causes it?

There are a variety of things that can fall under this type of failure. One of the best examples is a timing belt tensioner that won’t hold tension. If we were to reinstall a failing tensioner, the resulting repairs could cost thousands of dollars. These failures are rarely the fault of the driver. Typically, these things are parts that are well past their useful life.

How common is it?

We see crucially failing parts on about one out of twenty-five engines.

How do we fix it?

The exact fix will depend on what is failing. We will always do our best to get your permission before proceeding with repairs that exceed what you have already authorized. However, if it is not possible for us to continue without a certain repair, and we have been unable to reach you by phone, text and email for more than 3 hours, we may authorize up to $300 in additional repairs on your behalf.

Catalytic Converter Failure

What is it?

The catalytic converter, or “cat,” is an active filter that sits in the exhaust piping. It converts unburned fuel and other harmful pollutants into less harmful pollutants. It is monitored by the engine computer using a dedicated sensor located just downstream of the cat. If the cat isn’t doing a good enough job of cleaning up the exhaust gasses, the sensor will see this, and the check engine light will come on.

An underperforming cat may cause your car to fail an emission test. This failure will rarely cause your vehicle to underperform, but in extreme cases can cause a lack of power under acceleration.

What Causes it?

Catalytic converters wear out over time. The high temperature chemical reactions that take place in the cat will slowly become less efficient. Driving your car with an active misfire, out of specification fuel trims, or while internally burning oil may accelerate the failure. A faulty cat test sensor may cause the test to fail.

When we remove the engine from the car to perform the head gasket repair, we disconnect the battery. This resets the engine computer. When the computer is powered back up, it has to rerun all of its tests on the cat. If a cat was close to failure before, it may fail this retest. It may take a few days to a few weeks of regular driving for the vehicle to retest the cat.

How common is it?

Catalytic converter failure is pretty common on Subaru’s over 100k miles. The vehicles made from 2000 through 2015 seem to be more susceptible. About one in fifteen will see a cat test failure after head gaskets. Most will see this failure before 200k miles.

How do we fix it?

If the cat fails, the correct fix is to replace the cat. If the sensor fails, then replace the sensor. There are fuel system additives that claim to clean up the cat, but we haven’t seen any convincing evidence that these additives work well. Cats can cost anywhere from a few hundred dollars to two thousand, as they contain rare metals. The sensor costs a few hundred dollars to replace.


Acknowledgment of Receipt and Understanding

Once you have read and understand the above information, please enter your name and vehicle info in the spaces below. This will notify our team that you have received the above information. If you have any questions, please contact us at 720.295.0007, repair@subiesmith.com or use our web form.


I acknowledge that I have received the Subiesmith Head Gasket Complication Notice and that I have read and understand the policies.