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PT Was Overheating. Code P0300.

 
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Old 17 May 2016, 11:01 am
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Default PT Was Overheating. Code P0300.

I have an '08 PT Cruiser, base engine. This is kind of a long story so I'll try to shorten it. About 6 months ago, my PT started overheating on my way home from work. I discovered that my radiator was cracked so I replaced it. I also replaced my thermostat with a Failsafe thermostat (Don't do it). The failsafe failed and I was running with the thermostat stuck open (I didn't know it was stuck)for about a month or so. No heat, but everything else was fine. Just recently, the PT started to overheat again. I was also getting a rough start at idle and a P0300 code. I replaced the crappy thermostat with one that actually works and the Engine Coolant Temp Sensor. I bleed and burped the cooling system using both the radiator cap off, watch for bubble method as well as the bleeder valve method. The car runs fine for a few days without overheating but misfire remained. I changed out the spark plugs (the looked pretty bad but standard wear without coolant on them or anything like that) and the misfire is gone. Running great for 2 days without any overheats issues or misfires that I can tell. There was a "gurgling" sound in the dash though. Now, 3 days later, I started to overheat again this morning. I didn't let it actually overheat but the gauge went 3/4 of the way up until I cranked the heat up. There isn't coolant in my oil and there isn't oil in my coolant. No drips or smoking anywhere either. I burped the system again and more bubbles came out. I used my OBD II reader and I get a P0300 code but the dash light doesn't come on. The "gurgling" sound seems to get less and less every time I burp the system. What's going on here? Is it possible that I just didn't get all the air out and should burp it again? Both fans come on when they should as well. Please help! Also, I had the timing belt, water pump, alternator all changed almost a year ago.

Last edited by JJenn74us; 17 May 2016 at 11:11 am.
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Old 17 May 2016, 11:54 am
Fk5 Fk5 is offline
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Default Re: PT Was Overheating. Code P0300.

If you continually have to burp the system there are only two possibilities: 1. You didn't get all the air out the last time or 2. you have a leak. Often it is actually both. I don't know what the "wait for the bubble method" is, but I don't think that will work without a giant funnel. Otherwise, you are just spitting coolant on the floor.

Did you reset the codes? The 300 showing on the reader may be to indicate that there was a misfire recently (before the plug change) or that there is still a misfire. If the car is still running good, I would leave that alone for now.

Does the car use coolant? Do you have any leaks? Heater core going out? Start with a coolant pressure test and then maybe one of those block tests to see about a head gasket.

FYI, if you actually overheated the car, change the oil ASAP. Hopefully, you already did. Overheating is not good for the oil and it is cheap insurance.
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Old 17 May 2016, 01:53 pm
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Default Re: PT Was Overheating. Code P0300.

So the misfire code may still be stored in the cpu even if that problem is fixed? Can I unplug the battery to get rid of it? I really don't think it's a head gasket because there isn't a leak anywhere exterior or internal that I can see (no oil in coolant and no coolant in oil, no coolant on the ground as well as no coolant on the plugs when I changed them). The overheat is a slow and gradual process and only at stop lights, etc. and goes away when moving. No smoke is coming from exhaust (other than the normal on a rainy day). I'm at a loss at this point. I'm considering using Bars Leak Liquid Copper to make sure there isn't a small leak anywhere.

Last edited by JJenn74us; 17 May 2016 at 01:59 pm.
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Old 17 May 2016, 03:10 pm
Fk5 Fk5 is offline
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Default Re: PT Was Overheating. Code P0300.

Quote:
Originally Posted by JJenn74us View Post
So the misfire code may still be stored in the cpu even if that problem is fixed? Can I unplug the battery to get rid of it? I really don't think it's a head gasket because there isn't a leak anywhere exterior or internal that I can see (no oil in coolant and no coolant in oil, no coolant on the ground as well as no coolant on the plugs when I changed them). The overheat is a slow and gradual process and only at stop lights, etc. and goes away when moving. No smoke is coming from exhaust (other than the normal on a rainy day). I'm at a loss at this point. I'm considering using Bars Leak Liquid Copper to make sure there isn't a small leak anywhere.
Funny. I was going to suggest that something being clogged up might be the problem. Those leak fixes can be the cause of blocked up cooling systems. If you are worried about a small leak, is the car losing coolant? If it is, it is going somewhere. Start with a quick pressure test.

You say it only happens at stoplights, etc. Is it rev related? Maybe the water pump is shot/slipping? Is it speed related? Is the air going over the rad cooling it off?

Check and double check everything. Often it is something we fixed or monkeyed with that is causing the problem. You state the fans are working as they should, but with the problem only when stationary, that would be the first thing that I double check.

The codes stay in the memory for a time after the problem is fixed. I am not sure how long, but I think it goes in terms of cycles of start-warm up-shut off, etc. It is a diagnostic aid for intermittent problems and probably keeps people from scamming inspections.
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Old 17 May 2016, 05:05 pm
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Default Re: PT Was Overheating. Code P0300.

Quote:
Originally Posted by JJenn74us View Post
So the misfire code may still be stored in the cpu even if that problem is fixed? Can I unplug the battery to get rid of it? I really don't think it's a head gasket because there isn't a leak anywhere exterior or internal that I can see (no oil in coolant and no coolant in oil, no coolant on the ground as well as no coolant on the plugs when I changed them). The overheat is a slow and gradual process and only at stop lights, etc. and goes away when moving. No smoke is coming from exhaust (other than the normal on a rainy day). I'm at a loss at this point. I'm considering using Bars Leak Liquid Copper to make sure there isn't a small leak anywhere.
First thing I would do is make sure the coolant (radiator) AC fan is working.
Sounds like the dual speed fan has seen better days and they are not expensive at around $100 from rock auto, takes maybe an hour or two at most to replace them.
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Old 17 May 2016, 05:44 pm
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Default Re: PT Was Overheating. Code P0300.

I had that gurgling in my overflow and fixed it by putting in a new thermostat and radiator cap. My radiator cap was the wrong pressure and wasn't keeping the system sealed. No problems with it since.
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Old 18 May 2016, 03:10 pm
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Default Re: PT Was Overheating. Code P0300.

It appears I may have fixed the problem. I've burped it a couple more times and haven't overheated since (fingers crossed). It starts up fine and isn't smoking at all. I've driven it the back and forth from work without issues. I've idled in the driveway for 30 minutes at a time without any issues as well. The gurgling sound is gone. Looks like I had a fair amount of air in the system. Wish me luck!
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Old 18 May 2016, 03:16 pm
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Default Re: PT Was Overheating. Code P0300.

Quote:
Originally Posted by JJenn74us View Post
It appears I may have fixed the problem. I've burped it a couple more times and haven't overheated since (fingers crossed). It starts up fine and isn't smoking at all. I've driven it the back and forth from work without issues. I've idled in the driveway for 30 minutes at a time without any issues as well. The gurgling sound is gone. Looks like I had a fair amount of air in the system. Wish me luck!
Great news! (I hope) FWIW, when burping the system, it can help to park the car with the front higher than the back and use the bleed or the funnel method. I usually just fill it up and continually check it. They will take more coolant through several cycles.
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Old 18 May 2016, 03:23 pm
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Default Re: PT Was Overheating. Code P0300.

I would suggest keeping an eye on the coolant reservoir tank in case the coolant level drops as it might automatically bleed out more air.
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Old 27 May 2016, 01:56 pm
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Default Re: PT Was Overheating. Code P0300.

Okay....it started to overheat again yesterday. Maybe I'm just being cautious but it got to just under 3/4 up the temp gauge and that made me turn on the heater. That worked and dropped the temp down to 1/2. I got home, let it cool down a bit and opened the radiator. I couldn't see any coolant on top of the thermostat. I'm sure that the thermostat was still open as it was still fairly warm. Should I see coolant there? The overflow tank was still full. Anyway, I topped off the radiator with coolant and burped it again. Now it seems fine again. no problems at all. When I burped the radiator and it got to temp (opening the thermostat) there were small bubbles and when I gunned the RPMs up, coolant jumped out of the radiator about a foot or so. Maybe I just shouldn't have gunned it? It seems to be fine now so I really don't think the headgasket is bad. Again, no leaks anywhere externally or internally (no coolant in oil or oil in coolant. There isn't any smoke blowing out of the exhaust either. Both fans are coming on as well. If the headgasket was bad wouldn't it be more obvious? Any ideas?
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