Head Gasket Prep


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Head Gasket Prep


 

What you need to know before we get started:

What's involved in replacing the head gaskets.

What the potential complications are.

What the benefits of replacing the head gaskets are.

What additional repairs may be recommended.


Please complete the form below to confirm you have read and understand the information on this page. This is required before work may begin on your vehicle.

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What vehicle will you be bringing in for new head gaskets?
 

What's Involved


What's Involved


  • Start the Inspection Form
  • Power wash the engine and engine bay
  • Drain fluids from the engine
  • Disconnect the engine from the car
  • Remove the engine from the car and mount the engine on an engine stand
  • Remove the intake manifold
  • Power wash the engine
  • Remove the timing belt system
  • Remove the cylinder heads from the block
  • Prepare and clean the cylinder heads and block
  • Measure the cylinder head surface warpage
  • Measure the short block mounting surfaces for warpage
  • Complete the Inspection Form
  • Contact customer with any additional recommended services
  • Resurface the cylinder heads, if needed
  • Perform any additional authorized repairs
  • Reassemble the engine with new gaskets
  • Reinstall engine into vehicle
  • Fill with new fluids and purge any air bubbles in cooling system
  • Power wash engine bay
  • Perform thorough test drive of at least three miles
  • Inspect for leaks or other issues, address issues as necessary
  • Contact the customer to arrange vehicle pickup

Potenital Complications


Potenital Complications


Replacing head gaskets is a very involved repair, requiring many precise steps. This process can often reveal damage done during previous repairs or damage that was undetectable until the engine was disassembled. Here are some issues that may need to be addressed while replacing the head gaskets. 

 

Crankshaft Bearing Damage - Rebuild Short Block, Disassemble Cylinder Heads

The notorious rod knock. A common failure when an engine runs low on oil or overheats. Also caused by not changing the oil on time. Engines with leaking head gaskets will quickly run low on oil if not checked and topped off regularly. This issue may not become apparent for several thousand miles after the damage is done. This issue can sometimes be detected prior to the rod knock developing by the presence of metal flake in the oil, or in the bottom of the oil pan.

 

Piston Ring/Cylinder Wall Damage - Rebuild Short Block

Caused by a oil that is at a low level, oil that is beyond it’s service life or overheating. Piston ring/cylinder wall damage will result in the engine burning oil. A slight failure in the piston rings may require adding a quart of oil every 1000-1500 miles. A severe failure of the rings may require a quart of oil be added every 250-500 miles. You may see smoke out the tail pipe on acceleration. This issue is often undetected prior to fixing oil leaks, as the lack of oil is attributed to the leaks.

 

Damaged Bolt Holes - $30 each

Typically the result of a previous mechanic installing a bolt crooked or over tightening a bolt, damaging the threads the bolt threads into. This weakens the ability of the bolt to hold properly. Common locations of damaged threads are the power steering pump mounts, valve cover bolts and timing belt pulley bolts. The fix is to drill out the damaged threads and install a thread replacement sleeve.

 

Exhaust Weld Cracks - $80 to $200, if repairable

When removing and reinstalling the exhaust system, weak welds can break. This creates an exhaust leak. These don’t tend to be a functional problem, but will result in a loud noise.

 

Warped Cylinder Heads - $160 to resurface both

Warped cylinder heads are a common issue on Subarus that often contributes to the failure of the head gaskets. If warped cylinder heads aren’t resurfaced before installing the new head gaskets, the new head gaskets don’t seal for very long. If found out of specification, resurfacing the heads is required.

 

Warped Block Head Mounting Surfaces - Rebuild Short Block

This is a rare failure; typically caused by severe or extended time overheating. Failing to address this issue will result in shortened life of the head gaskets (similar to warped cylinder heads). To resurface the block surfaces, the short block has to be split apart and the crankshaft and pistons removed.

 

Cracked Cylinder Heads or Block - Replacement of the failed Component

This is a very rare failure which is caused by extreme overheating. Replacement costs will vary by used part availability. These failures may not be detectable during the replacement of the head gaskets. Detection of these issues usually requires further disassembly and machine shop testing.

 

Damage from Previous Repairs - Repair Varies by Issue

Damage caused by work done by other repair shops is not unheard of. In addition to damaged bolt threads, we also see issues such as scratches/scars on gasket sealing surfaces or missing bolts. These problems may not be evident until the repair is underway. 

 

Discovery of Other Needed Repairs

Once the engine is apart, other leaks may be identified. You are not required to have these other leaks fixed. However, it may be significantly less expensive to do so while the engine is out and apart. Other potential issues are: a worn out timing belt system, metal fake in the oil, or a worn out clutch.

 

Timing Belt Tensioner Recompression - Replace the Timing Belt Tensioner - $120

If we are not already replacing the timing belt tensioner, then the oil one will have to be recompressed. Most of the time this process goes fine, but sometimes the tensioner doesn’t properly hold tension after it is recompressed (this is more likely with old or aftermarket tensioners). If the tensioner is not holding tension, then a replacement is required.

 

Minor Leaks Showing After Major Repair

After fixing a major oil or coolant leak, previously unknown leaks may become apparent. When a major fluid leak has spread over a large area, it is difficult, if not impossible, to determine if other seals are leaking. We do our best to inform you of unknown leaks during the inspection, but this isn’t always possible.

Benefits


Benefits


What are the benefits of having the head gaskets replaced?

Stop External Leaks

Most Subaru head gaskets leak oil, and possibly coolant, externally. These leaks can drip off your engine and leave stains in your parking spot. They also drip onto the hot exhaust system, causing a burning smell. Replacing the head gaskets stops these leaks, keeping the fluids inside the system where they belong. 

Increase Resale Value

When selling your Subaru, having the head gaskets replaced and leak free will make your car easier to sell and will likely get a better price. Most people shopping for a Subaru know of the common head gasket leak and will want to know if that repair has been done. 

Reduced Risk of Damage

A leaking engine can put you at risk for further damage. Running an engine low on engine oil can cause a rod knock or the engine to seize, requiring new or rebuilt engine to be installed. Running low on coolant can cause your engine to overheat, resulting in warped, or even cracked, engine components. Any of these failures can leave you stranded and will cost much more than the head gasket replacement. 

Additional Services


Additional Services


Here is a list of the common recommendations made while replacing the head gaskets:

The following applies to any Subaru 4-cylinder, timing belt driven engine produced in 1998 or after. The frequency of the listed issues is a best guess based on years of experience and hundreds of Subaru’s serviced and assuming 120k miles on the vehicle. 

 

Timing Belt Kit with Water Pump

Frequency: Required by Subaru every 105k miles

The timing belt service is commonly due around the same time as the head gaskets begin to leak. Neglecting to replace the timing belt can result in severe internal engine damage, typically bending the valves. This kit includes a timing belt, hydraulic tensioner, three idler bearings, and a water pump. All are top quality brands. 

 

Rear Engine Seals

Frequency: 1 out of 2 leaks slightly, 1 out of 4 leaks heavily

All the seals on the back of the engine. These are the hardest to get to. Includes the rear main seal, the oil separator plate and the wrist pin access port o-ring.

 

Oil Pan Gasket

Frequency: 1 out of 4 confirmed leak, 1 out of 2 are hard to tell

A common leak that is often difficult to diagnose. This gasket sits just beside and below the head gaskets and rear engine seals. A leak in either of these items will quickly cover a portion of the oil pan gasket. This makes it difficult to determine if there is a leak in the oil pan, or if it is running down from the other gaskets.

 

Oil Pump Reseal

Frequency: 1 out of 4 leaks slightly, 1 out of 4 leaks heavily

The oil pump is sealed to the front of the engine, behind the timing belt, with silicone sealant and an o-ring. Also includes the front crankshaft seal, which is housed in the oil pump. Moderately difficult to access. Leaks oil. 

 

Camshaft Carrier Reseal

Frequency: 1 out of 6 leaks, 3 out of 4 are hard to tell

   -Includes: Camshaft Seals and Valve Lash Adjustment

   -The camshaft carrier is a large plate that holds the camshaft and seals in the cylinder head. This plate is sealed with a thin layer of silicone sealant. Adjusting valve lash is needed after servicing, and is included. This leak point is difficult to confirm as it is close to the cylinder head gaskets and valve cover gaskets, which tend to leak across it. 

 

Valve Lash Adjustment

Frequency: 3 out of 5 are out of adjustment

The amount of clearance between the rocker arms and the top of each valve has a very specific tolerance. Too much clearance and the engine will tick excessively. Too little clearance and the valve may hang open in the cylinder, causing a misfire and lack of power. A properly adjusted Subaru engine has a slight to moderate tick noise. This service requires removing the valve covers for access if performed later. 

 

Camshaft Seals

Frequency: 1 out of 3 leaks, 1 out of 5 leaks heavily

The camshaft seals keep oil from leaking out of the front of the engine, behind the timing belt, as the camshafts rotate inside the cylinder head. 

 

Spark Plugs

Frequency: 1 out of 4 have worn plugs, due every 30k to 60k miles

Spark plugs provide the point of fire to light the air/fuel mixture in the engine. All spark plugs have a limited lifespan. This service will be suggested based on the mileage of the last spark plug replacement, as interpreted by electrode wear patterns.

 

Spark Plug Wires

Frequency: 1 out of 2 worn

Failed spark plug wires are a common cause of misfires on Subaru’s. It’s a good idea to replace these wires every 100k to 150k miles. 

 

Oil Cooler Gasket

Frequency: 1 out of 4 of Subarus have this system, 1 out of 3 of these leaks

A secondary system that was equipped on many six cylinder, turbo charged or Forester automatic engines. Not difficult to service with the engine installed, but a common leak source. 

 

Drive Belts

Frequency: 1 out of 3 worn

Drive belts transfer the rotating energy from the engine to the accessories that provide power steering assist, electricity generation, and air conditioning. These belts wear out and develop cracks in the rubber. This will often cause a loud squeal or screech noise, especially when the engine is first started. 

 

Thermostat

Frequency: 1 out of 6 malfunction

Required if the engine was overheating

The thermostat regulates whether the hot coolant from the engine is sent to the radiator to be cooled or is routed directly back into the engine. A failure in the thermostat is a common cause for an engine to overheat. And this overheating is a common cause of failed head gaskets. 

 

Clutch Kit w/ Flywheel Resurface

Frequency: usually due at 100k-150k miles

Manual Transmission Only

This is the component in manual transmissions that transfers the rotating force of the engine to the transmission. Clutch kits have a limited life span, similar to brake pads. The rate that the clutch wears out varies based on driver habits and operating conditions.