ACtion Magazine - June 2014 - (Page 35)

Subaru EJ25 engine By Jacques Gordon The Subaru EJ engine series has a bad reputation for failed head gaskets, particularly the 2.5-liter version, but it's not due to a design defect. The turbocharged single-cam version of this engine has been popular for years among aircraft homebuilders who operate it at high power settings for long periods of time. This proves the engine's reliability, as long as it gets proper maintenance. Like many engines, this one has an open deck block. When an open deck engine is repeatedly overheated, the cylinders move (creep) and abrade the head gasket, eventually causing internal water leaks. On the Subaru engine, head gasket failure is usually a result of intermittent or repeated mild overheating and a gradual loss of coolant that goes unnoticed until it's too late. The question is, why does it seem to happen so easily on a Subaru? In other engines, the thermostat is heated by coolant ﬂowing directly from the hottest part of the engine; the cylinder head. On this ﬂat-four engine, coolant ﬂows from the head to the heater core and then to the thermostat. The heater core is the highest part of the cooling system. Imagine what happens if there is air in the system or if the heater core is partially plugged. Under either condition, the thermostat won't open all the way and coolant ﬂow is reduced. The engine will overheat under heavy load, like driving up a long hill, but return to normal after the load returns to normal. Often the driver doesn't notice or doesn't take action because the temperature always returns to normal. Until the day it doesn't. Subaru issued a recall (WWY-09) to address blocked heater cores. It was caused by a high chlorine content in the factory coolant that was corroding aluminum in the cooling system. The ﬁx is to ﬂush the system and reﬁll with Subaru's pre-mixed long-life coolant (SOA868V9210) and cooling system conditioner (SOA345001). You can also mix your own but be sure to use Subaru's unmixed coolant (SOA868V9270) and distilled water. A TSB (08-52-08) was issued to address gradual coolant loss, and the same malfunction can allow air to get into the system. As the engine cools down, coolant is sucked into the radiator from the reservoir tank. Debris sucked up from the tank can jam the radiator cap pressure valve open, preventing the cap from sealing. The reservoir tank will overﬂow and dump Intermittent overheating coolant when the engine is running, and if the coolant level falls low enough to empty the tank, air will be drawn into the system. The ﬁx is to clean or replace the radiator cap, clean out the reservoir tank, and shorten the suction hose slightly so it doesn't draw debris from the bottom. In addition to making sure the radiator cap and coolant reservoir cap seals are clean and working properly, it's imperative to get all the air out of the system when reﬁlling. There is no bleeder, so using a vacuum tool to reﬁll the cooling system is a good idea. ❆ Reader Reply June 2014 * ACtion 35 http://www.busacparts.com http://www.macsw.org/imis15/MACS/Publications/ACtion_Reader_Reply/MACS/Publications/ACTION/ACtion_Reader_Reply.aspx?hkey=ac24bddb-c045-442a-813c-cbf05f88ac4d

Table of Contents for the Digital Edition of ACtion Magazine - June 2014

A/C temperature testing
SAE Standard J2534-2
Save the date for San Juan
Saluting our troops
Outlook
Freeze Frame
Leonard's Law
Virtual View
Service Port
Last Watch
Member Profile
By the Numbers
Cooling Corner
Industry News
Association News
New Products

ACtion Magazine - June 2014