Are EJ2.5 SOHC Engines Prone to Overheating?

[Mike104]

I know the EJ25 DOHC are prone to overheating when the head gaskets go due to exhaust leaking into the coolant.

I thought the EJ25 SOHC are more likely to have external leaks that could possibly result in overheating if the coolant level runs low.

I've seen a number of older Subaru's for sale with the SOHC that complain about overheating (would stay away from since one wouldn't know how badly the lower end is) but was just wondering.

[idosubaru]

4 hours ago, Mike104 said:

I know the EJ25 DOHC are prone to overheating when the head gaskets go due to exhaust leaking into the coolant.

I thought the EJ25 SOHC are more likely to have external leaks that could possibly result in overheating if the coolant level runs low.

I've seen a number of older Subaru's for sale with the SOHC that complain about overheating (would stay away from since one wouldn't know how badly the lower end is) but was just wondering.

Yes. More often than not it's due to the headgaskets having already been replaced, cheap gaskets, poor quality job, etc, or someone limping them around with low coolant/other issues because the cars are getting older and lower value, hence more prone to poor maintenance, ignoring issues like coolant loss, etc.  Failure modes expand once the heads are off and gaskets replaced.

You're right, it would just be more accurate to say it this way:

4 hours ago, Mike104 said:

I know the EJ25 DOHC are prone to overheating when the head gaskets go due to exhaust leaking into the coolant.

I thought the EJ25 SOHC *with original factory gaskets* are more likely to have external leaks that could possibly result in overheating if the coolant level runs low.

Edited July 6, 2021 by idosubaru

[Numbchux]

Not any more than anything else that's approaching 20 years old. A lot of mistakes and neglect can happen in that time.

 

My '00 has been well cared-for, and I wish it would run warmer. Only on the hottest days do the coolant temps get above 180, when it's below zero outside, it barely gets over 160. I'm thinking about replacing the OEM stat with a cheap aftermarket one to let it warm up a bit.

 

OEM SOHC headgaskets usually leak oil externally. Overheating is more often caused by dirty radiator, failed fans, plugged heater core, etc.

[GeneralDisorder]

It can happen. And if well maintained - probably WILL be the eventual failure that you encounter - or a rod bearing. 

Eventually any Subaru engine (most modern engines in general really) will experience a head gasket fire ring failure. It's the nature of aluminum blocks. It moves with respect to the gasket and has NO FATIGUE LIMIT. That is, unlike iron (steel, cast iron, etc), it does not have a limit below which it can sustain an essentially infinite number of cycles. Aluminum, when exposed to ANY AMOUNT of stress, will have some number of cycles which will cause failure. This can and does result in head bolt threads giving out, gaskets abrading the surface of the head and block, etc. Most people here and on other Subaru fan groups fail to understand on a basic level that Subaru engines ARE NOT FOREVER. In fact they are typically single-use when you take into account the risk vs. reward equation, cost of rebuilding vs. cost of replacement, etc. Especially when high performance applications are considered. We only build engines from 100% new parts for example. 

But the most common HG failure on those engines is external oil leakage - from the back of the driver's side head and from the front of the passenger side head. 

GD

 

[nipper]

Also a stuck thermostat, clogged or decrepid radiator, bad cap can cause over heating. Its an old car. Old cars can overheat. Just on Subarus one tends to suspect HG. Actually on any old car that can be suspect.

[1197sts]

Also Radiator fans, and Air Conditioning temp sensors when inop cause the #2 fan to not work.