Fluctuating Temp Gauge

So I've had my Suby for 2 weeks now, and I've been getting the hang of driving a 5-speed. I put about 20 miles on it today, and noticed that my temp gauge was not holding steady I've attached a pic of the range it sweeps once warmed up.

 

Both radiator fans seem to be on once it warms up, even though no A/C or defrost is on. Is that normal? I tried to pin down a pattern in the fluctuation and this is what I noticed: When cruising at speed in 5th, the gauge will rise to the top red mark in the pic. When I go thru the gears from a stop it will go back to the lower red mark (ie normal.) And repeat. I've read multiple threads on thermostat and HG issues but couldn't find this exact problem so I started my own thread.

 

What do I need to check/replace? Thanks in advance...

Check to make sure the car has coolant in it. Then find out where it's going.

Ok, went out today to check fluid levels and found that the Upper Radiator Hose was collapsed. I couldn't see any coolant leaks under the car or around the connections. The reservoir is full. Removed the radiator cap and the Upper Radiator Hose expanded to normal size. I start the car and let it warm up for 30 minutes. Fans begin cycling normally, temp rises to normal and stays there. I try cutting the heat on full blast, it doesn't get hot just lukewarm. Hose never collapses and temp never fluctuates. Shut it down and come inside for 5 minutes. When I go back outside the Upper Radiator Hose has collapsed again. Reservoir fluid level is same as when engine was cold and off. I've attached pics to illustrate what I saw. I've never seen an URH do that before, so what does it mean?

Get a new cap. Fill the motor with coolant. see what happens.

Get a new cap. Fill the motor with coolant. see what happens.

10-4 good buddy. Subaru dealer only or Vatozone cap?

Stick with oem if possible

OK. I'll call the dealer tomorrow

Dealer had to order the cap, will be here by next week. Going to replace the upper radiator hose also just as a precaution.

Not sure how much you are aware of Subaru's coolant issues, but you need to fill the block from the upper radiator hose first. Otherwise it will not get enough coolant by filling the radiator.

Low coolant= no heat and sometimes collapsed hoses as it tries to get more on shutdown. The full overflow is because it's hot and the pressure is pushing what you have in the system out.

 

O.

Not sure how much you are aware of Subaru's coolant issues, but you need to fill the block from the upper radiator hose first. Otherwise it will not get enough coolant by filling the radiator.

Low coolant= no heat and sometimes collapsed hoses as it tries to get more on shutdown. The full overflow is because it's hot and the pressure is pushing what you have in the system out.

 

O.

 

I'm waiting for a new cap, and I'm installing a new Upper hose tomorrow, along with more coolant. Anything else I should replace while I'm at it? And do you mean to add the coolant via the vent plug hole? or directly into the hose before reattaching it to the radiator?

And I wasn't aware of coolant issues with Suby's. I'd heard of the 2.5 head gasket issues but that's it...

Via the hose. The vent only fills the radiator.

 

Not issues with cooling but with ridding the system of air (ie burping).

Reason? The t stat is on the bottom of the block while 90% of other vehicles they are on the top. this doesn't allow much water to pass through the t stat until it is open. Subaru T stat and Stant's Xactstat have a small hole with a jiggle valve in it. It allows some fluid to pass through but not a lot when filling the system.

This design was changed with the FB engines.

 

O.

Thank you for all the info, brother

Update 1/2/15

 

Got the new radiator cap in today. Replaced that and the upper radiator hose. Also, I took the excess fluid from the reservoir and put it in the radiator. Started the car, warmed up and didn't go over normal temp on the gauge. Had the heat on full blast but it still only gets lukewarm. Shut it down and waited, upper hose has not collapsed. Will take it for a drive in the morning to see if the temp stays normal.

 

Oh yeah once it cools down I'm going to open the vent screw and check the fluid level while it runs again. Anything else I should do?

Forgot to mention that the fluid level in the reservoir stayed at full. It did not fill back up to where it was before.

Fill the radiator. Start, let it run with bleed screw open. Add until you start getting overflow. Tighten and run. The system will draw what it needs from the reservoir. It wouldn't hurt to leave the screw/cap open overnight, on an incline if possible.

 

O.

So let it get up to temp with both the vent screw and cap removed? and then put them back on. But leave the system open all night? Just want to be 100% clear

OK I ran it with cap and screw off until it started coming out of the valve hole. I didn't have to add any coolant, is that normal? And the heat inside the car is still only warm at best.

Is normal. As the air gets out of the system the heater will work better.

Each time you run it to temp and turn it off the system will draw in coolant.

Sometimes (like in your case) it just is a royal pita to get all the air out. To help it, when parked for the night for the next few days take the cap off.

 

O.

Thank you for your help, Osei!

Update: put another 40 miles on the car today, temp gauge held steady at normal. Going to go out and take the cap off for overnight. Thanks again for your help Osei.