What is the head warp tolerance for a Subaru?

Head Warp Tolerance for a Subaru
Subaru specifies that the allowable amount of cylinder head and engine casting warpage must be no greater than 0.035mm (0.0012 in.). The maximum grinding limit to correct a warped cylinder head is 0.1mm (0.004 in.). The flatness of the heads and engine castings is critical to the performance of multilayer steel (MLS) gaskets.
In some cases, professionals may resurface Subaru heads as a matter of course not only to remove any warpage but also to ensure that their heads have the proper surface finish before installation. The successful use of an MLS gasket requires that the head and engine casting mating surfaces be smooth.
If the warpage exceeds Subaru’s grinding limit, there could be potential piston to valve clearance issues, and it may be necessary to consider using a thicker head gasket to address the situation.
It’s important to note that Subaru heads almost never warp due to the super compact size and design, which results in minimal warping. However, in cases of severe overheating or head gasket failure, there’s a good chance the cylinder head or block is warped.
In summary, the head warp tolerance for a Subaru is specified to be no greater than 0.035mm (0.0012 in.), with a maximum grinding limit of 0.1mm (0.004 in.) to correct a warped cylinder head. Resurfacing the heads may be necessary to ensure proper surface finish for the installation of multilayer steel gaskets.

Why are Subaru head gaskets so bad?

The problems started when Subaru started using a composite head gasket in some of their car models from 1997 to 1999. The device features a multi-layer steel shim coated with a graphite layer. It was not up to the mark and allowed coolant to leak into the exhaust pressure and combustion chamber.

At what mileage do Subaru head gaskets fail?

between 100,000 and 150,000 miles
The original head gaskets on a Subaru 2.5 engine tend to fail between 100,000 and 150,000 miles. Most replacement gaskets last just as long. Will the repair cause other problems for my Subaru? Head gasket replacement usually goes smoothly and doesn’t cause any other issues.

How do you check for a warped head?

Set your feeler gauge at . 003 inch, and place the gauge between the straightedge and the cylinder head. If the feeler gauge fits in the gap, then your cylinder head is warped and must be machined flat. Set the straightedge at the other corners diagonally, and check the gap with the feeler gauge.

How do you prevent a Subaru head gasket from failing?

Here are some examples of what not to ever let happen.

1. Change your Subaru’s coolant on a regular basis. This is one of the most important things you can do to your Subaru.
2. Know what is being used in your Subaru. Not all auto parts, services and repairs are created equal.
3. This is a biggie, and the most overlooked.

How much cylinder head warpage is acceptable?

about 0.003-inch
Always check with the automaker’s tolerance specifications, but a generally accepted maximum warp is about 0.003-inch on a V6 deck, 0.004-inch on a V8 deck and about 0.006-inch on a straight-six deck. The head deck is then checked in the opposite diagonal direction.

What causes cylinder head warpage?

Overheating is the most common cause of cylinder head warping and cracking. When an engine gets too hot, the cylinder head often bears the brunt of the pain. This causes the components to warp and pressure to leak.

Are Subarus known for head gasket issues?

A number of Subaru models are affected, however the most common failures include the 2.5 Liter SOHC engine used in the late 1999-2004, Forester, Impreza, Outback and Legacy. Signs and symptoms of engine head gasket failure include: Engine overheating. Unexplained loss of engine coolant without an obvious sign of …

What is the tolerance for a head gasket?

Most aluminum heads using a multi-layer steel (MLS) head gasket should have no more than 0.002-inch (0.05 mm) of total distortion (block plus head combined) in any direction.

Can a warped head be fixed?

If the warping is not too severe, the head is usually just resurfaced. This restores a flat mating surface to the head, so that it can seal to the block with a new head gasket.

What is the dimension tolerance of a gasket?

Standard Gasket Tolerance.
+/- 0.5mm is a good tolerance for most rubber based flange applications.