I still hate my cooling system

[Hoser]

Round 1 of the issue: My Cooling System: I hate it!

Synopsis: Car intermittently overheats in stop-and-go driving. It also has been guzzling coolant like a sailor on shore leave.

I took the car to the mechanic who pressure tested the cooling system. He said he found a small leak at the heater core under pressure but not much. He agreed that it wasn't enough to explain significant coolant loss in a couple of days.

Tonight I wound up doing a lot of stop-and-go driving in cool weather. I noticed the temperature gauge rising and pulled over. I sat for about 90-120 seconds then turned the ignition on to see if the temperature was starting to come down, and was surprised to see that it was perfectly normal. I drove around for a while, more stop and go, and the temperature gauge remained right where it should be. After about ten minutes I noticed it creeping up again. Again I pulled over, waited a minute or two, and then turned the ignition on and the temperature remained normal. It remained normal for another 15 minutes of stop-and-go driving.

I had plenty of heat in the car the whole time. I'm willing to believe that I have a tiny leak in the heater core but I don't think that's the root cause of my overheating and coolant loss. It just doesn't feel right to me.

Is it possible for a thermostat to intermittently stick closed? That seems like it would explain what I was seeing tonight-- the car getting hot but very rapidly returning to normal temperature. An intermittent fan, maybe? Could a flaky water pump cause this? Is it possible that overheating is the cause of the coolant loss rather than vice versa?

The car is a stock 2005 Touring convertible with just under 150K miles.

[chuzz]

I'd replace the thermostat and radiator cap, if it were mine. Call it preventative maintenance. Check the hose from the radiator overfill spout to your overflow jug too and make sure there are no cracks or holes in it. NitroPT can recommend a sealer for the leak in the heater core. I THINK it's a Moroso product, but can't recall. Also, did your "mechanic" check to make sure both of your cooling fans are operating properly? If not, have them checked.

[Hoser]

The radiator cap was just replaced. The mechanic also put a ceramic sealant in, but for some reason he didn't tell me what brand it was.

I'm reasonably certain that I've heard both fans come on. That doesn't mean that they always do, of course.

[MJKnight]

This sounds a little crazy but I have found that if you run the front of the car up on ramps..
Remove the cap and fill the system let it sit a bit and refill it..
I had the same problem you did...and this worked...for me ...also there is an air bleeder on the filler neck

[NitroPT]

Originally Posted by MJKnight

This sounds a little crazy but I have found that if you **run the front of the car up on ramps..
Remove the cap and fill the system let it sit a bit and refill it..
I had the same problem you did...and this worked...for me ...also there is an air bleeder on the filler neck

**Elevating the vehicle on the side the radiator is mounted is always a good tech tip.

The PT Cruiser contrary to wide spread responses only had cooling system issues that were directly related with steam pockets in the heads of early 1999-2002 production castings during a cooling system repair or replacement of a head gasket. The concern was corrected in the head casting design also other air bleed components added for better initial bleeding from a dry or at least 50% capacity cooling system filling.

If you fill a PT Cruisers cooling system with a 2.4 engine manufactured date from 2002 late production and newer the system will self bleed after a cycle or 2 assuming the FSM procedure was followed, naturally the fluid was filled and checked correctly after one engine cycle.
All cooling system temperature problems can be easily found with most all vehicles with a few tools, a *note pad and a couple of simple cooling system test equipment.

I enjoy helping but at times it is frustrating to see common problem threads like this never to read someone looking up or create your own problem solving tree from information and recommendations to help resolve problems. Many FSM have them and sometimes some of us forget how useful they are and take them for granted.

[Hoser]

I'm a software engineer with very little knowledge of mechanics. I have a good brain for spotting symptoms, testing, and putting together a diagnosis and I'd probably be a good mechanic if I invested the time to learn, but my upbringing gave me very little knowledge of mechanics and I've always just outsourced. Asking questions like this helps me learn things, so that I can better make sense of what the mechanic is telling me and sometimes call BS on him.

This morning the radiator was full when I checked it. The overflow wasn't, so I remedied that. Made the hour+ drive to work with no issues.

[chuzz]

Sounds like progress. Keep an eye on the overflow jug. There's a cold level and a hot level. Anywhere in the range is good.

[NitroPT]

LOL... My starting higher education in this lifetime was aligned to be a Paleontologist.
However a Motorcycle, a brain and FORD ended that!




If you had to fill the reservoir tank I doubt the mechanic forgot to, I would say you still have a problem overlooked.

[Hoser]

Oh, I'm sure I have a problem. I just am trying to narrow down what it might be and get a better understanding. The fact that it sometimes starts overheating and then recovers essentially immediately makes me think it's a problem of coolant circulation.

[NitroPT]

well cooling systems do not necessarily always need a reservoir...

I have to actually change out the coolant in mine because it starts to get fowl from not re-circulating coolant.