Subbie Riddle... What would cause an Outback to overheat only when cold?

[coswoll]

I have  2001 Subaru Outback 2.4L Automatic wagon with about 190K miles. It runs great, however when it gets below 40 degrees farenheit, it has a few symptoms that are not present when the weather is warm.

 

1. Strong odor of gasoline, so much so that I cannot turn on heat unless the car is moving and wind is forcing the order to leave the engine area.

2. Overheating when driving more than 5-10 miles, regardless of uphill or downhill.

 

At the end of last winter, I replaced the thermostat, drained old coolant, then refilled the system with 50/50 coolant to make sure I had a proper mix. Sure enough, I drove about 10 miles, and immediately saw the engine begin to near the red line. After this, I brought it to a mechanic and asked them to look for any problems and possibly check the water pump. They gave it back to me and told me the water pump wouldn't fail the way it is engineered, and they claimed that it had to be a head gasket problem. I don't believe they actually checked anything out because they didn't charge me after leaving it with them for three days.

 

So, I saved up a little cash and it was around May, when things started to warm up. When I was ready to bring it in to have the head gasket replaced, the weather had consistently risen to 50-70 degreees farenheit and I was no longer having overheating issues. I was testing it on hills, and with AC on full, trying to get it to overheat with no success. So, I figured even if they replaced the head gasket, I couldn't verify that their work was successful until it got cold again, so I didn't do it. Now that we've had a couple weeks where mornings are below 30 degrees, all the symptoms are back, and they seem to be worse when it is really cold than just cold.

 

I don't have anyway of proving that the gas odor and the overheating are related, but I never have one without the other. If I lived in a warmer climate, I don't think I would even be aware that there is an issue because it drives great in the summer and I have no issues, even on long road trips with the car packed and AC on full blast.

 

Other info... I didn't see any excessive rust or metal particles when I flushed the coolant, I've always changed the oil regularly and i've used synthetic oil since it cleared 100K, no major mechanical failures but have replaced starter, alternator, knock sensor, belts when worn. Timing belt changed at 125K. Flushed & changed transmission fluid at 150K. I've regularly replaced spark plugs, spark plug wires, & distributor cap, but I've never replaced the fuel filter or anything fuel related because I was always afraid of a spill and stinking up the garage and having to hear my wife complain for weeks while the smell went away. Please help me!! I've aked every mechanic that I've randomly run into and they only tell me that it's either thermostat, water pump, or head gasket, however none of those suggest that it would work fine in the summer but overheat and stink in the winter. Any insight and explanation could help. I'm at a loss. I don't want to spend $1500 for a head gasket replacement and find out that it was some other anomoly that only costs me $50. I love my Subbie and hope to get her to at least 300K miles.

 

 

[coswoll]

Also forgot to mention that there are no issues with the ratiator fans. They come on when needed, i've monitored them both when engine was running hot and when engine was running fine with AC running.

[presslab]

Pull out the thermostat and see if it overheats.

 

You sure you don't have a fuel leak? Don't mess around with this, it could burn your car down. Hoses often leak at the clamps when cold.

[Fairtax4me]

Gas smell is often the filer tube. It has a plastic cover on it that catches and traps all the dirt salt and moisture from years of driving and causes the filler to rust out. Replacements are about $120.

 

Overheating when cold is due to the thermostat not opening. And this can either be caused by a clogged or partially clogged heater core, a partially clogged bypass hose, or a cruddy aftermarket thermostat.

[coswoll]

I may be idiotic... but wouldn't the thermostat have opening/closing issues whether the outside temperature was hot or cold? I would think after 5 minutes of driving in cold or warm, it would be at a regular running temp and outside temp wouldn't make a difference. Let me know your thoughts?

[Monkeybus]

I'd pull it out and run it, see if anything changes. A Thermostat is very easy to remove and replace. 

[MilesFox]

The thermostat sits on the cold side of the cooling system If an aur bubble hangs out in there, the block can boil over and the radiator remains cold, because the thermo needs a volume of coolant to work.

 

I solved an overheat problem in a 2001 outback by replacing the cap and thermostat, as well as the engine temp sensor (intermittent temp spiking, and hrd starting when hot)

 

Any time you are opening the cooling system, it is recommended to fill the engine block via the upper hose first, before taking on any in the radiator, and then run the car to add the rest, and be certain the thermostat is open and the coolant is cirvulating before throwing on the cap and calling it a day.

 

You may want to hod the RPM past idle to work out air bubbles and force the thermostat open.

 

Adhere to this advice or secede to the realm of blown head gaskets. This is not grandpa's chevy, so a lot of that 'common knowledge' simply just won't apply with a subaru's cooling system

[ivans imports]

Check clamps on intake feul lines when your done doing the head gaskets

[JKinPA]

I agree with the others here...the easiest diagnostic you have for your overheating problem is to pull the thermostat out and see if the car overheats.

 

As far as the fuel smell goes I would check the metal and replace the rubber fuel lines and fuel filter.  I have a wife too and yes spilled gas smells but it is no where near as bad as the smell of a car fire.  This is not a convenience fix item this needs to be addressed ASAP.

 

Especially the rubber lines.  When it gets cold the cracks in those rubber lines are more open and remember it's NOT the liquid gasoline that is most volatile it's the fumes or vapor, and that is what you are smelling.

[WoodsWagon]

I may be idiotic... but wouldn't the thermostat have opening/closing issues whether the outside temperature was hot or cold? I would think after 5 minutes of driving in cold or warm, it would be at a regular running temp and outside temp wouldn't make a difference. Let me know your thoughts?

To add to what Fairtax4me said, the thermostat operates based on the return flow from the heater core. That's the only circulation of coolant around the thermostat when its cold and isn't open. So if the heater core is plugged, then there may not be enough flow to heat the thermostat after it gets through heating the interior.

[ilvbugs]

Coswoll,

 

Check your email, sending you my phone #...I live in Salt Lake and can help you.

[later_Peter]

"burp it"

[ivans imports]

seized water pump ?

[Bushwick]

It should be easy to tell which end of the car the fuel smell is originating from, either under hood or near the fuel tank. Old rubber will harden, and on colder starts fuel might be leaking past a clamp.

 

Are you sure it's actually overheating? Is the coolant actually in the overflow and is coolant level correct? I'd buy a cheap mechanical coolant gauge, install it's probe (no need to mount gauge inside, just attach to coolant flow and monitor from engine compartment) and observe the readings. It's also possible for the radiator rows to get clogged with minerals from tap water (reason why you need to run distilled water) or the fins can get clogged over time from overly dusty roads or gravel road dust. Both situations will cause actual high temps once the thermostat is open as it can't actually cool, even with the fans forced on (like running the AC switched on with heater).