Thermostat fail AGAIN within 2 years 2011 Legacy

[SuperAkuma]

2011 Legacy 2.5i with about 190k on it. Bought it brand new.

On November of 2021,  the top radiator hose popped out of the radiator while I was driving. Car overheated but lucky I was close to home. Did some research, found out my thermostat was stuck open/closed forgot which one but I had to replace it.  Put the car on the lift and replaced it an OEM thermostat with all new OEM fluids. 

Fast forward to today June 2023 same thing happened again. Lucky I wasn't to far from home either. The car didn't overheat this time but I saw smoke coming out the hood. Got home, checked the top radiator and sure enough it popped out.

What would cause the thermostat to fail within 2 years?  I probably drove about 15k on it since the last time I replaced it. Is it just bad luck that it happened or are there other underlining issues that I need to address? It is close to 200k and I need to do the timing belt, so I will get it all done at once. 

[m sprank]

Sure its the thermostat again?  Maybe you lost a head gasket now.

[SuperAkuma]

3 hours ago, m sprank said:

Sure its the thermostat again?  Maybe you lost a head gasket now.

I am not sure. Would a blown head gasket cause the radiator hose to pop out? Also how would I test it?

[creep_nu]

once you get the hose on and coolant in again...run the engine.  once up to temp if you see air bubbles coming up the expansion tank that's usually a pretty sure-fire way to tell.  next would be a compression test and/or using one of those color changing head gasket failure thingies you can get from autozone or whatever (Loaner Block Tester - Find the Right Part at the Right Price | AutoZone).

 

 

just spitballing but could be something as simple as the radiator cap being dead and overpressurizing the system?  did the hose clamp just break?  did the radiator hose give up the ghost and split somewhere?   did the thermostat get installed upside down(with the jiggler thingy at 6 instead of 12) and through a series of unfortunate events cause an air pocket by the thermostat...reduced flow and blah blah.  i ain't no mechanic so i have literally no idea how possible 2 of those 4 scnearios are but...just thinking thoughts

[m sprank]

My money is on HG as the OP previously overheated.  I dont think the upper rad hose gave out.  I think its a "Im not mechanical and have no idea really what is what" and is referring to the breather going into the reservoir. 

 

Cheap and easy test is a combustion gas leak test.  Not always the most accurate with small leaks.  But it should work for your needs. 

 

 

[SuperAkuma]

No I am not a professional mechanic by trade but I have no issue working on cars. When the upper hose gave out, it just popped out just like the last time that it happened and IT was the thermostat.  That is what I was going by. 

Going to do the combustion test on Friday when my friend bring over the tester.

JW, if the head gasket was bad, would that CAUSE the thermostat to fail or are the two conditions separate? 

Just thinking head, IF the head gasket is GOOD, what other reasons would the thermostat fail pre-maturity? 

There are no milky fluid in the radiator or the oil dip stick this is why I am thinking it could be a bad thermostat AGAIN.  I am just hoping for the best. 

[SuperAkuma]

On 6/22/2023 at 1:24 PM, creep_nu said:

once you get the hose on and coolant in again...run the engine.  once up to temp if you see air bubbles coming up the expansion tank that's usually a pretty sure-fire way to tell.  next would be a compression test and/or using one of those color changing head gasket failure thingies you can get from autozone or whatever (Loaner Block Tester - Find the Right Part at the Right Price | AutoZone).

 

 

just spitballing but could be something as simple as the radiator cap being dead and overpressurizing the system?  did the hose clamp just break?  did the radiator hose give up the ghost and split somewhere?   did the thermostat get installed upside down(with the jiggler thingy at 6 instead of 12) and through a series of unfortunate events cause an air pocket by the thermostat...reduced flow and blah blah.  i ain't no mechanic so i have literally no idea how possible 2 of those 4 scnearios are but...just thinking thoughts

Saw this post late so I will do the air bubble test tomorrow but on Friday, my friend is coming over so I can do the combustion test. 

The upper rad hose popped off, it didn't crack or break. The clamp was still on the hose when it popped off. 
The thermostat didn't get installed upside down. If it was, it would of failed a long time ago. I drove from Sac to Seattle 3 times(about 700 miles each way 1400 miles total) since I replaced the thermostat. 

[m sprank]

Sounds like the system is overpressurizing. Like exhaust gas would do. Otherwise there is no reason for a tstat to fail that quickly. You could have an obstruction.  Did anyone put something in the coolant?  Is the heater core clear?  Is the waterpump flowing properly?

[MoleMan]

On this. If it's the HG then the OPs car would be blowing white smoke out of the tailpipe.  It's it's mild then the coolant would start to get milky.  OP are you losing any oil at all?

As M. sprank has pointed out one thing.  I always when changing thermostats will put a new Upper/Lower Rad hoses on as well as flush and fill the system. As well as new clamps all around.  I have never had any issues doing it this way.  Sometimes the old coolant and the new T-Stat don't mix.  Generally have to watch the car coolant level for a week or so when the system is "Burping"

[SuperAkuma]

12 hours ago, MoleMan said:

On this. If it's the HG then the OPs car would be blowing white smoke out of the tailpipe.  It's it's mild then the coolant would start to get milky.  OP are you losing any oil at all?

As M. sprank has pointed out one thing.  I always when changing thermostats will put a new Upper/Lower Rad hoses on as well as flush and fill the system. As well as new clamps all around.  I have never had any issues doing it this way.  Sometimes the old coolant and the new T-Stat don't mix.  Generally have to watch the car coolant level for a week or so when the system is "Burping"

No white smoke out of the tail pipe.
Coolant not mikly.
Car this age, I have to add about 1/2 or 2/3 quart oil before the next oil change(5k)

Last time did the thermostat, I flush new subaru blue coolant, did not change upper/lower hose and yes I did burp the system. 

Update
Just did the a coolant gas combustion test and it did NOT change color. 

[m sprank]

One good thing. 

Maybe the hose is just shot and needs to be replaced. Could be swelling with heat and pressure.

[SuperAkuma]

Another update

On Friday I bought a new rad cap, upper and lower rad hose, new tstat and 4 new hose clamp, all OEM from the dealership.

 

Today I did one final test on the temp, running the car. While running I squeezed the upper AND lower hose. I squeezed it pretty hard this time because I was getting frustrated.

I let the car idle and revved up the engine ri get to temp. Around 205*F the fan kicked in but it didn't go any higher and the temp started to go down. Touched the lower hose and it was just as hot as the lower hose. Seems like it is working fine now. Let it ran for another 15 minutes, temp never got over 210.

So it seems like it is working now.

To be on the safe said I am planning to change our the tstat while I am doing the timing belt replacement. It is a little early but just want to get this over with it.

While I am doing the timing belt, anything I should inspect that is related to this issue?

 

I am guessing it could be a stuck tstat or a clogged radiator. When I squeezed the lower hose, I blew whatever out. I am just guessing but it seems plausible.

I am open to any possible reason on what happened. 

 

[silverton]

I've seen the upper hose connection fail; where the rib that the hose clamps behind is broken off and only the smooth portion of it is left.  This in conjunction with engine movement could eventually pull the hose off of the radiator.

[DrD123]

18 minutes ago, silverton said:

I've seen the upper hose connection fail; where the rib that the hose clamps behind is broken off and only the smooth portion of it is left.  This in conjunction with engine movement could eventually pull the hose off of the radiator.

I have seen that as well, unfortunately (sort of a been there, done that) - from my own vehicle earlier this year.

[SuperAkuma]

26 minutes ago, silverton said:

I've seen the upper hose connection fail; where the rib that the hose clamps behind is broken off and only the smooth portion of it is left.  This in conjunction with engine movement could eventually pull the hose off of the radiator.

Yes the rad hose can pop out and break off the radiator, but that does not explain why it was over heating after I put it back. Bottom hose was cold so no coolant was circulating. 

[Infosecdad]

Sometimes you can get an air bubble on the thermostat that prevents it from opening until bled out.  There are a number of things that could cause that behavior, sounds like your engine has hopefully moved past it (fingers crossed).

[silverton]

Yeah you very likely had a big air bubble that needed to be burped out after reconnecting and topping off.  Kind of a pain in the ass but I've had great success bleeding cars quickly by very slowly pouring the coolant in.  the weight of the coolant can keep an air pocket from being able to bleed itself out when poured in too quickly. But it is still a process that can take 45-60 minutes of idling with the radiator cap off, I use a bleeder funnel and allow the fans to cycle on and off two to three times. If the fans DON'T turn off it is not properly burped yet. The fastest I've had a car properly burp itself is 25-30 minutes of idling.

Are you positive it was a failed thermostat?  Usually they fail open, but I have seen in rare cases they don't.  Did you test your thermostats in boiling water with a temperature probe? They do start to open at a lower than indicated temperature, but they should be fully open by the temperature stamped on the thermostat.

[SuperAkuma]

Doing the timing belt right now and this is what I noticed.

Some nasty build up on the water pump. Didn't have much time to inspect it but it looks like the weeping hole is clogged?

Also the top radiator has chip that broke off at the end. Maybe the plastic clogged the radiator?

 

[DrD123]

You'd need an awful lot of plastic bits to clog the top of the radiator, I would think - a few chunks from the inlet aren't going to be a big deal.   Looks like you have 2/3 or so of the ring sitting in your hand, so probably not much more (assuming some is probably in the upper radiator hose, too)