[8lug]

Hey, I'm a bit used to mechanics of a old V8's... not this new stuff. I have a couple major clues here on the overheating.

My wife's '06 Tribeca occasionally starts overheating when she idles, the temp gauge goes up to 4/5ths or so. Then it hovers between 50% and a little over when moving.

The big odd clue is that the engine was hesitating to idle upon cranking, rough for the first 20 seconds, or until you mashed the gas once. It happened for a few weeks, so it wasn't simply bad gas. For a couple weeks or so, we were hearing a metal scrubbing squeak noise too.

But then one day my wife called and said she thought the engine died, it was sputtering, apparently made some clunky noise, and some shrills . Found out in the mix of these issues, that the coil pack on cylinder 1 wasn't connected well. So I fixed that.

So it's cranking, idling fairly well on crank, and running fine... except we get the overheat when stopping at long traffic lights, etc. I don't hear any more odd noise anymore. Weird weird. unno:

I've checked oil and coolant levels... they are clean and staying at level. We do have some oil drips. Valve cover gaskets have been replaced, and plugs. Might be a slight head gasket or main seal. Just a few drops a day kind of thing.

I've pondered water pump failure, like maybe it exploded and the noise my wife heard was it tearing up the metal bits???

Maybe the thermostat is stuck closed???

 

[81vwcountry]

at idle is your electric fan running.it is variable speed controlled the hotter the engine gets the faster the fan will run. that would be my first thing to check. dont sound like head gasket issue because it would normally build up pressure and push out water. do you loose heat during this. if so restriction somewhere or bad water pump. hope this helps out running a engine hot takes a toll on them.

 

[Witmarquzot]

I just did this about a year ago. Root of the issue was that the cooling system unable to hold pressure.

Radiator cap is the simplest and cheapest check as it is probably original
Replacing the cap may uncover a pinhole leak when it gets warmed (50%)
Thermostat would be next, stuck partially open/ closed
What ever you do, DO NOT put radiator fix liquid in.


If the pump is gone, you may look at replacing the engine assembly as the water pump is attached to the timing chains inside the assembly.

 

[8lug]

@81vwcountry, the fan does come on when it heats up. I need to drive it myself sometime, and check if it helps with the cooling. It seems like it just cools down once you get moving again... as if it were an old air cooled vw

I haven't noticed any coolant leak... I did put some in a few months ago though. I'll have to look around again @Witmarquzot.
Is the thermostat on the lower radiator hose?
I was afraid of that about the water pump, that it was hidden up in the chain alley. That'll suck if that's what it is.

Any way to test the water pump to determine without ripping into it?

 

[Witmarquzot]

Thermostat location


You can pull a hose from the upper left side and see if coolant sprays out, messy but simple.

 

[8lug]

:tup:

 

[tdelker]

Very unlikely to be water pump.

Most like cause of difficult to locate overheating is internal headgasket leak, especially after an overheating even caused my something else (like a bad radiator cap).

There are good videos on how to diagnose: Look for bubbles in the coolant reservoir at idle and under revs.

Tom

 

[idosubaru]

1. check and monitor the coolant level ***in the radiator***. ignore the overflow tank for the moment. is the radiator level lowering after a week or so?

2. clogged radiator. you can pull it and flow test it. it should pass the volume of a regular home water hose. i wouldn't typically expect this to present at stop but stranger things have happened and you're describing poor idle issues.

3. check and/or replace the radiator cap with a Subaru one.

4. check and/or replace the thermostat.

5. headgasket - they typically overheat and do not stop - they keep going straight to red once they fail internally so you either don't have a headgasket or it's a very initial stage HG failure exhibiting atypical symptoms.

 

[idosubaru]

it is not the water pump. if someone says that just act like they didn't.

 

[idosubaru]

for the noise - you need to pull the serpentine belt and check the idler pulley bearing and tensioner pulley bearing.

personally i would just replace them - they fail *all the freaking time*. I consider them 60,000 mile maintenance items for that reason.

buy a $5-$10 6203 bearing and bang the old one out and tap the new one in. super easy. they come out and go in easily if you've ever done a bearing before. any old hammer and some sockets will work. takes no time at all.

don't loose the small nut on the back side of the tensinoer pulley bolt - it's a capture nut and falls right out once the bolt is removed. wedge something behind it so it doesn't drop out.

 

[tdelker]

"5. headgasket - they typically overheat and do not stop - they keep going straight to red once they fail internally so you either don't have a headgasket or it's a very initial stage HG failure exhibiting atypical symptoms."

I respectfully disagree with this. I would say the vast majority of the experience on this board reflects that the internal HG failure on subarus results in moderate overheating with occasional significant overheating events under heavy load.

The rest of your info I concur with 100%, including using a rag to stuff behind the tensioner to keep the nut from falling off!

 

[idosubaru]

I respectfully disagree with this. I would say the vast majority of the experience on this board reflects that the internal HG failure on subarus results in moderate overheating with occasional significant overheating events under heavy load.

oh yeah, you're right on this engine. good catch. there are other subaru engines with internal leaks that do overheat instantly every time they run hot....but not H6's...at least initially.

 

[8lug]

I changed out the tensioners a couple years ago, but yea worth look at again. They were at least spinning with the engine running. Previous time that happened, it ate the belt though.

I didn't lose the nut that time... but I did lose the bolt in the grass. I had to pull a bolt off the center jack plate under the vehicle... worked like a charm. No shop nearby sitting on the side of the road! :naughty:

Good point... I've not actually checked in the radiator... been trusting the overflow tank.

Wouldn't a blown HG give smokey exhaust, or milky oil?

 

[idosubaru]

I changed out the tensioners a couple years ago, but yea worth look at again. They were at least spinning with the engine running. Previous time that happened, it ate the belt though.

I didn't lose the nut that time... but I did lose the bolt in the grass. I had to pull a bolt off the center jack plate under the vehicle... worked like a charm. No shop nearby sitting on the side of the road! <img src="http://www.sb9t.com/forums/images/smilies/naughty.gif" border="0" alt="" title="Naughty" class="inlineimg" />

Good point... I've not actually checked in the radiator... been trusting the overflow tank.

Wouldn't a blown HG give smokey exhaust, or milky oil?

No they don’t fail those ways. Frankly no Subaru in 30+ years fails headgaskets that way. Only if theyre insanely bad, so bad you wouldn’t be asking about it here. Similarly, compression tests are usually useless as well.

 

[lutek34]

Get combustion leak tester, and run test if you have combustion gas in your coolant.

 

[8lug]

Quick check this morning, I opened the radiator cap, nearly freezing temperature outside, and it was pressurized. "Tssssssss" for 3 or 4 seconds with the cap opened a bit.

I gotta get some coolant and see if it'll take any.

 

[tdelker]

Combustion leak tester rarely catches the exhaust gases in the coolant. Many report false combustion gas test, but positive for bubbles in overflow tank and finally fixed with headgasket.

Pressurized cooling system when cold is a strong indicator of exhaust gases leaking in to coolant system.

Tom

 

[Jefferson]

I thought that the throttle body oring caused this although no one could explain why. There is a thread about it.

 

[lutek34]

and it was pressurized. "Tssssssss" for 3 or 4 seconds with the cap opened a bit.
.

are you sure it was pressure, not vacuum?

 

[8lug]

Nah, I can't be positive that it wasn't vacuum instead of pressure. Gut feel was it was pressure, but I didn't think to put my hand around it to check.

Sooo, the radiator is low... likely very low. I put about 1/2 gallon of coolant in it. Note, the overflow was sitting on the low mark, steady level for weeks. I cranked it and let it run a minute. Maybe I shoulda let it get hot, hmm.

Anyway, my bet is that the coolant is leaking into a cylinder over many hours, thus the crappy startup we were having (when it had enough coolant in it to leak to the cylinder). I'm gonna crank on it after a few hours and see.