Subaru Outback Forums banner

1 - 17 of 17 Posts

·
Registered
Joined
·
23 Posts
Discussion Starter #1
2000 OBW, 136k, was running fine before doing head gasket just leaked a lot of oil. New water pump, timing belt and tensioners 6 years ago (25k miles). Car runs fine post surgery, but now the temp gauge does not move from cold, not even a little. Fans come on at 203 degrees but temp continues to rise as per odb2 sensor. Heater hose at firewall on pass side gets warm, on driver's side stays cold. Radiator hose at bottom is cold, at top is warm. Temp got to 233 in a hurry. Stumped. There's only one temp sensor, I think, and it turns on the fans, but gauge not working. I've done the burping thing but can't do it long as it gets hot quickly. Now what?
 

·
Registered
2008 Outback Wagon 2.5i limited
Joined
·
118 Posts
I’m not sure by your post if your head gasket repair was just done or 25k ago. But it sounds like there may be an air bubble in the system. That happened to me on my HG repair, but it should fix itself. Try leaving the cap off the radiator while idling. Maybe have to do a few cool down cycles to work it out.
 

·
Registered
Joined
·
23 Posts
Discussion Starter #3
Head gasket just completed. Water pump, etc. about 25k ago or 6 years...we don't drive it much. How can I let it idle when the temp keeps rising?
 

·
Registered
07 OBW 2.5i 4EAT; Eastern Ontario, Canada
Joined
·
16,541 Posts
There's only one temp sensor, I think, and it turns on the fans, but gauge not working.
Yes, there's one engine coolant temperature sensor, but three wires from it. One is a ground, one goes to the ECM for engine/fuel and fan control, and the other goes to the gauge in the instrument panel. If the gauge remains at the "C" (doesn't move at all), then there could be a discontinuity between the sensor and the instrument panel (.g., broken wire) or a fault in the sensor.

However, even if the temperature gauge (but not the ECM) isn't connected to the sensor, it wouldn't cause the engine to overheat. The ECM is obviously getting the engine temperature signal, and the fans are turning when they should.
Fans come on at 203 degrees but temp continues to rise as per odb2 sensor.
At 203 F, do both fans turn on, or only one?

Heater hose at firewall on pass side gets warm, on driver's side stays cold. Radiator hose at bottom is cold, at top is warm.
Notwithstanding the possibility of a lot of air in the cooling system (which is a possibility), if the coolant temperature is reaching 203 F, then the hose going to the cabin heater core, and the hose coming out of it would normally be close in temperature when the heater fan is off. That's because there should be constant coolant flow within the engine (even with the thermostat closed) as well as from the water (aka "crossover") pipe on top of the engine, to the heater core, and then out from the heater core to the inlet side of the water pump. If one of the heater hoses is hot, while the other is cold that could indicate limited, or no, circulation. (See attached)

Is this is a North American, LHD, 2.5, non-turbo?

Incidentally, looks as if there's two threads on this same topic, the other being https://www.subaruoutback.org/threads/stuck-thermostat-after-head-gasket.515348/
 

Attachments

·
Registered
Joined
·
23 Posts
Discussion Starter #5
Thanks for your reply, plain. Both fans come on. The heater does work now. Upon last startup my OBD2 scanner said the temperature was 233 degrees by the time I shut it off, and my temperature gauge was starting to move a little bit. The lower radiator hose was still cold, upper hose warm, radiator cap cold and could easily open it ... barely warm. I used a thermometer and it said it was about 100 degrees. The crossover pipe was warm but not hot... I could touch it. I'll give it a couple more attempts the I think I will just get to the shop... it's only about half a mile and all downhill ;)
 

·
Premium Member
2001 VDC/SC One of a Kind
Joined
·
12,173 Posts
So your post here: https://www.subaruoutback.org/threads/stuck-thermostat-after-head-gasket.515348/post-5889395 and what you posted above tells me that the coolant is not circulating through the heater core. As I posted on the other thread concerning this issue, you HAVE TO get the engine rpm up to 3-4k rpm a few times to force the air out of the heater core. You get it running and snap the throttle to quickly get it to 4k rpm and let off the throttle. Do this a few times until you get constant heat from the heater inside the car. Once you have heat in the car, continue to run the engine until you no longer have air bubbles coming up. When you no longer have air coming up, turn the engine off, let it cool for a bit, then put the radiator cap on after topping the radiator.

And as suggested on the other thread, a No Spill funnel is a great help in getting the coolant level above the engine and heater core as well as being able to see the coolant flow and when the air bubbles cease. They are relatively cheap at any part store.
 

·
Registered
Joined
·
23 Posts
Discussion Starter #7
Thanks, cardoc. I did rig a funnel to work as a no spill and have done the snap-rev thing. There is heat in cabin now. Is it ok to let it run even though the scan tool says it's 230+ degrees? Should I ignore the obd2 scan tool and just watch the dash gauge? Shouldn't the lower hose get warm or is it not because air is keeping it from opening the thermostat. Just afraid of hurting anything after all this work.
 

·
Registered
2006 OutBean, 2005 LGTW
Joined
·
1,053 Posts
Lower radiator hose is cold--you either have an air pocket or your thermostat is shot. Pull it and test it on the stove or just replace it with a new one.

When refilling, pull the upper radiator hose and fill the engine through it, reattach, then top the rest of the system up with coolant, then go through the motions snapping the throttle like cardoc suggests.

I've had some success squeezing repeatedly on the lower radiator hose to break the air pocket there free--sometimes.
 

·
Registered
'10 3.6R Outback Limited, 2zr swapped Toyota Yaris track toy, '05 AWD Pontiac Vibe
Joined
·
204 Posts
I've had some success squeezing repeatedly on the lower radiator hose to break the air pocket there free--sometimes.
This has also worked for me while the front of the car is up on ramps. I squeeze it hard and quick enough where I can usually hear/feel the jiggle pin moving and air bubbles will make their way to the filler neck
 

·
Registered
Joined
·
23 Posts
Discussion Starter #10
Tstat brand new. I can hear the juggle pin when I squeeze hose. I've squeezed, I've jiggled, I've burped, I've snapped the throttle, I filled the block through top hose. I don't think my temp sensor is working right cuz it says hot but nothing is hot. Gonna take it in to be safe. If I had a fancy infrared thermometer...
 

·
Registered
Joined
·
23 Posts
Discussion Starter #12
True, dyqik, but the one I had in there worked just fine before the head gasket and the new one is right from the Subaru dealer so I'm pretty sure the thermostat is good.
 

·
Registered
Outback 2011 3.6R Premium
Joined
·
757 Posts
Why don't you try removing the thermostat to test what happens. If it warms up correctly then you know either the thermostat is faulty (or installed wrong) or there was a large air pocket preventing the coolant circulation.

This is a very quick and easy test to see what happens.

If you have the old thermostat you can cut out the middle section (leaving the outside rim) and use the outside rim with the gasket to get a good seal.

Seagrass
 

·
Registered
Joined
·
23 Posts
Discussion Starter #14
Update: so as not to waste more time and throwing more money at sensors or anything else I decided to take it to my local mechanic. Turns out the plug to the coolant temperature sensor wasn't quite snapped in all the way are you kidding me? I worked on that thing for at least 10 minutes after it didn't run right the first time and it felt snug but just that half a millimeter was the difference between it running like an absolute kitten and pretty much hardly running until the ECU figured out what was going on so thanks for all your help! if anybody else has this trouble in the future, make sure that coolant temperature sensor connection is plugged in all the way!
This was my first head gasket ever (I'm 64) and I haven't torn apart a motor since my 327 in my 64 Impala (wish I could have that one back). I have done all the maintenance on my 96 Dodge Grand Caravan for the last 22 years however but pretty proud of myself for **** near getting this job 100% right - 99. 9% isn't bad!
 

·
Registered
'10 3.6R Outback Limited, 2zr swapped Toyota Yaris track toy, '05 AWD Pontiac Vibe
Joined
·
204 Posts
glad to hear it is all sorted. This reminds me of the time I decided to replace the head gasket on my '02 Toyota Echo just so I could learn how to do it. I had finished a gruelling two weeks of exams and wanted to know how to do a HG job so I went to work. 2 days later the car was back together and would crank but not start...rechecked timing and everything checked out fine. It cranked fine and sounded great but wouldn't start...towed it to the only mechanic I trust with my cars. He calls me the next day and tells me the car would run with his scanner hooked up the the car but it would die when unplugged. I forgot to re connect a single ground wire on the back of the block and the engine was grounding through his scanner. Yup, learned that lesson, I even thought about that being the issue but couldn't find a loose ground anywhere...
 
1 - 17 of 17 Posts
Top