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2001 Forester
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Discussion Starter #1 (Edited)
2001 Forester running hot after timing belt/WP replacement - Solved.

I must be overlooking something.......

I replaced the timing belt, water pump, and thermostat on my MIL's 01 Forester in August. Everything went fine and she has only needed to run short trips since. Today as she was headed out of town, she noticed the temperature was getting near red and drove to our house to borrow our car.

I did the regular checks and all seemed good. Went on a test drive and the temp was fine in heavy traffic for 15 minutes then kept going up. I turned the heat on and that dropped the temp. I got back home and while checking things over, found the lower radiator hose cool. I bought a bad thermostat thinks I.

Replaced the thermostat, again. Drove it for twenty minutes. It was better but still pushed 2/3 to the red and when I stopped the lower hose was not as warm as I expected.

Reservoir tank is clean, cool and not bubbling so HG is not on my suspect list.

Any ideas?
 

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2014 Impreza Ltd CVT
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Did you plug the radiator fans back in? That's a very common oversight by the weekend mechanic.
 

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2001 Forester
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Discussion Starter #4
Yes. Plugged back in and that was one of the first things I checked. They are running when the temp is at the half way point. What strikes me is that they were blowing cold air when the temp gauge was 2/3 to red when I noticed the lower radiator hose cool so coolant didn't appear to be circulating through the radiator......coolant is full.

I did a test last night on the first thermostat(the one I put on when I did the TB/WP). I put it in a pot of water on the stove and heated and it just starts to open at 85degC. Full open at 90degC. The rating on the stat is 77C so its hotter but I don't know if that would be enough to make the car run near red.
 

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02 Forester L (sold) Manual
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You're on the right track I think, the water doesn't sound like it's circulating. I've not done any coolant work on one of these, but you may have an air pocket in the system somewhere. On some cars I've owned it can be a little tricky to get the air bled out of them. Fill it with the heater on. May help if the nose is jacked up a bit to get the radiator fill higher than the rest of the car. Squeeze the upper hose a few times and try to 'burp' any air out. On some of my 'other' cars this is essential or the coolant simply won't move. You're just cooling the same liquid in the radiator over and over which is why the lower hose is cold.
 

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98 Fozzie
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You're on the right track I think, the water doesn't sound like it's circulating. I've not done any coolant work on one of these, but you may have an air pocket in the system somewhere. On some cars I've owned it can be a little tricky to get the air bled out of them. Fill it with the heater on. May help if the nose is jacked up a bit to get the radiator fill higher than the rest of the car. Squeeze the upper hose a few times and try to 'burp' any air out. On some of my 'other' cars this is essential or the coolant simply won't move. You're just cooling the same liquid in the radiator over and over which is why the lower hose is cold.
Bingo! Though the neck is the highest point anyway so the bubbles will surface as long as you are on flat ground. I wont guess here, I know that this is your issue. Take the 20-30 minutes and do this because that is probably how long it will take. Run it just like ddavidv said with the rad cap off and the heater blowing. Your goal is to continually top off the coolant and burp the bubbles out. If the top of the coolant level is rising simply squeeze the top hose slowly but consistently and you will see the bubbles come up, then the coolant level drop will coincide with how much air you are burping. Add a little bit more coolant (make sure its mixed!) and repeat until there are NO bubbles at all coming out. This will solve your problem.
 

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Either a bubble or the Tstat is installed incorrectly (I feel like I remember reading that its possible to install it backward and it won't open correctly then).
 

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2001 Forester
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Discussion Starter #8
After questioning every detail, my sanity, having the sinking worry that it could be HG......... It is fixed!!

I picked up a Subaru thermostat, gasket, and lil' bottle of Subaru branded coolant additive (figured it couldn't hurt). When drained and pulled the Autozone thermostat and compared it to the Subaru thermostat, I could see the Subie one was over 1/4in longer. Installed the thermostat, filled coolant and test ran. The temperature was rock solid when warm and never went higher than the first tick mark above 1/3rd. Also, the lower radiator hose was nice and warm, indicating I had flow thru the radiator and back.

Couple of notes on the Subie thermostat:

Making it longer means you cannot install it backward. The spring end can only face up. It will not fit if you try to place it the other way. I had the AZ thermo in the correct orientation but it did not open properly , BTW.

I think the more important reason for the spring section to be longer is that this places it in a more direct path to coolant flowing into the pump. Important on this engine which has the thermo near the bottom of the engine.

Thanks everyone for their replies! :woohoo:
 

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2001 Forester
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Discussion Starter #10
Thought a pic might be more helpful. The one on the left is from the dealer. On right from AZ the brand is Duralast.
 

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2014 Impreza Ltd CVT
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Thanks for posting. This has been discussed here in the past. The need for using Subaru parts in certain area's of the boxer engine.

Another is for the front O2 sensor. I know some have had good luck with some OEM sensors, but the majority end up with a Subaru part there also.

IIRC also the Subaru thermostat isn't that expensive either.
 

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2008 2008 2.5i-2018 XT
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Ona related issue. I was going to replace the radiator cap with a Stant. They looked so physically different I decided not to. Yet I went to Subaru and they didn't have an OEM one.
 

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2004 2.0 X
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440 Posts
Did you plug the radiator fans back in? That's a very common oversight by the weekend mechanic.

Where do you check that this has been done? I dont think Ive ever heard mine come on! (had belt changed 30k km ago).
 

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2014 Impreza Ltd CVT
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Where do you check that this has been done? I dont think Ive ever heard mine come on! (had belt changed 30k km ago).
When removing the fans, each has a plug on the bottom. After replacing them, it's very common to bolt them back in , but forget to crawl back under to plug the fans back in.
 

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2004 2.0 X
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So if I slide under and have a nosey? Thing is (From memory) there is the plastic grey 'shield' in the way?
 

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2014 Impreza Ltd CVT
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Yes, you will have to remove the 'belly' pan, OR you may try to see or feel from the top to find the connectors and if they are plugged properly.
 

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Ok, will have a look. It should be easy (common sense) to notice where to undo the belly pan?
 

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03 forester XT 2.0
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Yes. Plugged back in and that was one of the first things I checked. They are running when the temp is at the half way point. What strikes me is that they were blowing cold air when the temp gauge was 2/3 to red when I noticed the lower radiator hose cool so coolant didn't appear to be circulating through the radiator......coolant is full.

I did a test last night on the first thermostat(the one I put on when I did the TB/WP). I put it in a pot of water on the stove and heated and it just starts to open at 85degC. Full open at 90degC. The rating on the stat is 77C so its hotter but I don't know if that would be enough to make the car run near red.
Your radiador is plugged.
 
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