Questions on overheating of 2.2 and 2.5 Subaru engines

[ThosL]

I have noticed overheating problems seem particularly acute with Subarus, I can't remember another brand of vehicle that seems to be prone to this.  

 

I have a number of questions of how people can avoid problems due to overheating.

 

In the case of radiators, fans, the coolant system, the water pump, outside weather and climate effects, heavy hauling or substantial up hill terrain challenges, leaks, etc., what are the preventative measures that should be taken and measures that should be taken after a problem develops with 2.5 and 2.2 engines?

 

Is the hot/cold sensor on the dashboard a reliable measure of threats to having the engine overheat?

 

How high does the dial have to go up before a real threat to the integrity of the engine develops?

 

Does letting the vehicle cool off change the dynamic of the water flow in the radiator, the overflow, and throughout the engine?

 

How long should a Subaru be allowed to cool off if it overheats before it is restarted?

 

Why is a hot engine hard to start?

 

If the water pump is going bad, how much water does it leak, does the water only come out of it or other places in that case,  how much notice do you have before it must be replaced?

 

Why is the 2.5 more prone to permanent damage and does the 2.2 installation replacement significantly impact the power available as well as strain it inordinately when in a station wagon?

 

Are synthetic coolants or other forms of extraordinary options worth considering to augment the cooling system?

 

Thanks for responses to these questions.

[987687]

In the case of radiators, fans, the coolant system, the water pump, outside weather and climate effects, heavy hauling or substantial up hill terrain challenges, leaks, etc., what are the preventative measures that should be taken and measures that should be taken after a problem develops with 2.5 and 2.2 engines?

 

Make sure your radiator isn't clogged or old, you have a subaru thermostat, and the system is full of coolant, it'll be fine.

 

Is the hot/cold sensor on the dashboard a reliable measure of threats to having the engine overheat?

The temp gauge isn't the best, it favors the middle. When I was having issues with one of my cars I was watching a OBD2 reader for temp rather than the gauge, the temp gauge doesn't start to budge until about 220 degrees. I found out there was a problem because the engine was running at 195 F on the highway cruising along. Since 195 is cooler than the engine gets sitting idling in traffic, the temp gauge was right in the middle, but that's unacceptably hot cruising along the highway on a cool day. So a digital readout will help know if you're in an acceptable range for the driving you're doing.

 

How high does the dial have to go up before a real threat to the integrity of the engine develops?

It's more of a how long rather than a how high issue. If you drive with the gauge pegged for a long time, you likely overheated the oil and did damage to bearings. If the gauge starts to peg and you shut down immediately, you probably didn't harm anything (although there's clearly something wrong to begin with...)

 

Does letting the vehicle cool off change the dynamic of the water flow in the radiator, the overflow, and throughout the engine?

Say what?

 

How long should a Subaru be allowed to cool off if it overheats before it is restarted?

Until you figure out why it overheated and added coolant... If the temp is back down to normal, run it. and watch the gauge closely.

 

Why is a hot engine hard to start?

Partly because the computer will be giving it less fuel due to the fact fueling is in part based off engine temperature, the compression might be a bit low if oil is cooked off the rings

 

If the water pump is going bad, how much water does it leak, does the water only come out of it or other places in that case,  how much notice do you have before it must be replaced?

In my experience the only thing that really fails on the WP (at least if you replace it at the 105k mile timing belt interval) is the bearing, the seal will leak if an idiot installed it last.

 

Why is the 2.5 more prone to permanent damage and does the 2.2 installation replacement significantly impact the power available as well as strain it inordinately when in a station wagon?

The 2.5 is temperamental about being overheated and abused, I don't know why. I have a 2.2 in my 2000 outback and it's annoyingly slow.

 

Are synthetic coolants or other forms of extraordinary options worth considering to augment the cooling system?

The cooling system works fine if the radiator is in good shape, you have a subaru OEM tstat and don't have headgasket issues. If you really want, go get a dual row aluminum radiator.

[ThosL]

Does letting the vehicle cool off change the dynamic of the water flow in the radiator, the overflow, and throughout the engine?

Say what?

 

I was thinking that with a bad water pump leaking water (I am adding around a gallon every time I restart the car) you add water when you restart the car and unless there is enough water in the system abnormalities will happen especially because the water pump is not working.

[987687]

You're losing a GALLON!!!!!!!!! Every time you let the car sit? Yea, you have a serious problem. That's a big enough leak you should see it hemorrhaging from somewhere.

The cooling system is only like 2 gal or something, so losing a gallon is a serious problem, you need to find that.

[ThosL]

I had Monroe check it out, they said water pump.  I went to a couple other places that did not get a flashlight and get under it to diagnose.

[987687]

So get under there with a flashlight and find out where it's leaking. Where in newengland are you? Maybe someone near you would stop by and take a look or something. I've helped and been helped out by locals on this board before.

[idosubaru]

a gallon is excessive - it needs fixed. 

 

 

unless it's leaking externally it's not the water pump.

you never actually told us what vehicle engine though i assume it's an EJ25?

 

don't let the needle get up into the red.  anything above normal is not ideal, but the red or close to red is bad.

 

there's no strict rule like "at 194 degrees every engine ever made will get destroyed".  it depends on assembly, prior care, and probably very minute things like heat transfer characteristics, conductivity, dynamic loading.  there's no answer to your question about "when does damage occur" because it's an unknown differential equation with unknown variables.

 

there's nothing that can be done to mitigate the issue - except dont' run it hot or out of coolant.

change the coolant

add coolant conditioner to 2000+ (and 99 forester and impreza RS) Ej25's.

it has been suggested that the conductivity of the coolant may be a partial culprit so a good charging system and measuring voltage in the coolant may be helpful.  if that's true...

[ThosL]

I'm having the mechanic in Waterbury work on it tomorrow am;  I will just have to keep the radiator full and keep my eye on the gauge on the way up.

[keith3267]

I think one big problem is that the manufacturers of all makes and models expect the driver to be constantly looking at the instrument cluster instead of the road.  Its hard to notice a light coming on or a gauge creeping up until it is too late.

 

They put a chime to alert you if you don't buckle your seat belt, door ajar or god forbid that a $100 battery might go dead from leaving your lights on, but a $6000 engine?  Not a peep.  They should program the chime to sound off anytime the engine or transmission is in danger from low oil pressure or overheating.  Maybe there would be fewer owners needing head gaskets prematurely.

 

Hey Subaru, ya listening?

[987687]

Yes, actually. They don't even put a temp gauge anymore. They put a warning light now. Maybe it dings, I dunno. Never seen a newer one overheat.