Running Hot Randomly

[Prospeeder]

Well, this has me baffled, when it does it, has no relation to RPM, Speed, outside temprature, a/c operation, or the fan coming on.

It has a brand new Radiator, Waterpump, thermostat, heater core, Rad cap, Headgaskets, the correct 50/50 mix, Brand new premium Temp sendor.

Its not overheating really, but damn close it gets hot, like 3/4 of the gauge for no reason, it will be 105 all day and the gauge will sit dead middle, well now its just started creeping up out of nowhere, doesnt matter if im in drivethrough or highway, 70 degrees or 105. Nothing will make it come down it just does. By the time im able to stop and open the hood, the temp went back to normal.

The only thing not replaced, the uppper and lower hoses. This had me thinking, when i did my timing chain, i was filling it up, and i revved it up when i put the rad cap on, and it sucked the upper hose flat. I thought that was abit strange.....Also the system will not build pressure, I have defected out 3 radiator caps now and tested them, they work great, my system just doesnt build pressure. What the hell is going on!

[Buick_powa]

Thermostat is closing when not needed this happens on jobbers t-stats

[Prospeeder]

this is my 3rd thermostat still with the same issue. That was my thought exactly, but when i opted for the exspensive premium line thermostat and it still did it, Im not sure what to belive... I thought the lack of building pressure and the collapsing hose might be somthing, I guess Im gonna replace the rad hoses, there only 8 bucks each, heheh

[Prospeeder]

Well I think I may have a fan motor or coolant temp switch goin out or somthin. It finally got the hood open when it was gettin hot, the fan wasnt running, but the fan sputtered, came on then off, then on again and stayed on and cooled the car right down. hmmmmm

[SilentWing]

That's strange about the fan, almost sounds like a loose connection somewhere. Maybe trace all the wires first and make sure that's not your issue, but hopefully it's an easy fix... still seems really strange that it was sucking the hose flat though. I've heard all kinds of stories about the radiator cap, but after having three of them I don't see why that would be an issue either. If it's a broken wire maybe engine vibration is causing it to cut in and out?

Almost forgot to mention, if I remember right I got a radiator cap from autozone, and although it was listed in their system as the right cap it wasn't... that's obviously not your issue since you've seen the fan cutting in and out, but worth noting if you still have the hose issue.

[Prospeeder]

I would really like to know why the system doesnt build pressure. I can drive 50 miles, and stop and the hoses have no pressure and i can take the cap off like nothin. Im going to take that fan connector off and see whats up. Test some stuff out.

[SilentWing]

Yeah, keep us posted... did you by chance get a cap with one of those vents? I've heard those are junk too, and unless you were really leaking antifreeze badly you should have pressure.

[Prospeeder]

ohh yea? 2 of the three i tried are lever vents, and thats whats on it now. hmmm i think im gonna just get a normal cap.

[SilentWing]

Yeah the lever vents are garbage, i've heard that from a few guys... hopefully that fixes it

My fiance said also check the line that goes from the coolant resivour to the radiator because it's common for gunk to get clogged in that and that can cause them to go flat. Take the hose off and flush it out with a garden hose or high pressure water source.... then flush the bottle out too until no more gunk comes out, take the cap off make sure the radiator is full and fill the resivour and that should solve the problem. He said the vent caps tend to leak and don't work right, basically they're junk.

Also with your fan it could also be the relay so check that too

[6000]

Clogged overflow line, and/or bad cap will cause the hose to collapse on cooldown.

Do you have a pressure tester? If not get one, make sure the radiator is topped off, and pump up the tester. Watch the gauge to see how fast the pressure leaks down, and check for coolant leaks.

Fans constantly go bad, I'm changing electric fans almost every other day. Often the bearings inside the motor wears out. I did one today on an Acura, then i took the motor off the fan assembly, hooked to to my cell phone car charger, applied an air drill to the motor, and made a compressed air powered cell phone charger!

As for why it doesn't build pressure... does your engine have bleeder screws for the coolant? If you have them, and you didn't crack them open when you filled it, try that.

[Prospeeder]

No bleeder screw. The car hasnt done it for awhile now, so i havent been able to track anything down.... I still cant get pressure to build in the system, its just odd, my other cars, including my 3.1 Turbo Grand prix builds tons of pressure in the system.

[6000]

Try removing the upper radiator hose from the radiator side, and pour antifreeze directly into the hose until it fills up. Hook it back up and see if it builds pressure.

[SilentWing]

That's strange that they didn't put any bleeder screws on your car, mine has two of them... also strange that it's still not building pressure... did you try flushing your resivour? Or are you just leaving it alone since it stopped for the time being.

[Prospeeder]

Yea Its nice and full of coolant, I actually filled it up through the open hole int he block where the thermostat goes, then put the stat in and then fill it up. Iv had this engine complelty apart and its coolant passages are clean inside and theres definatly not a bleeder screw.

[Prospeeder]

I got pressure now!!! I tried another cap and it worked perfect, non lever vent type. Havent got hot once yet!

[Pontiac6ksteawd]

Just found the thread. I was gonna say if it aint building pressure, then the intake gasket aint right, or the rad cap is not letting the system build the pressure. Without correct pressure, the system can, and does, overheat.

But you figured it out, so nevermind :)

[Prospeeder]

Eek intake gaskets, lol, i just Did headgaskets up on this thing 10k miles ago

[Prospeeder]

aww it just did it again in my driveway. i think i need to replace the coolant temp senser for the ECU/fan circuit.... The hoses got REALLY tight like i was sorta scard. Then i saw some coolant steam from the front of the rad somewhere, and smelled it. And I looked everywhere but no luck, so i ran to turn the heater on high, and the gauge was nearly in the red, and suddenly the fan kicked on, wwwrrrrrrrrrrr and the temp started lowering and the hoses got soft, and it went back to normal..... so ya damnit. Maybe the super pressure made it spray from the rad hose or somthin, im not losing coolant nor does it smell anymore. Maybe i need another cap, wtf.....shouldnt it have bled off that pressure?

[Pontiac6ksteawd]

Otis, over on that other board was having some odd cooling fan issues too. He had to replace the ECM to fix it.

[turbokinetic]

The sputtering noise from the cooling fan would make me look at the fan relay or motor its self. Could be burned contacts in the relay or wore out brushes in the motor.

Funny about the hoses sucking flat. Had a BMW a while back that was towed in with overheating and loss of water. The owner had capped off the coolant overflow port (don't ask why) and when the engine would idle, it would suck the upper and lower rad hoses pancake-flat! The problem was..... coolant heated TB hoses had been replaced and connected to vacuum instead of the coolant port on the manifold!!

[SilentWing]

I highly doubt it's the cap again, 9 times out of 10 the cap will hold less pressure than specified not more. Chances are your hoses had 16psi in them since it was trying to stop your coolant from boiling, the hotter the coolant gets it will bleed pressure off slowly into the coolant resivour. You might want to check the hose going to the resivour again because if it was getting that hot and it started leaking coolant and now it doesn't, it seems like the hose to the resivour might be broken since it would appear that it was trying to bleed off the pressure you wrote about into the resivour but it leaked out. 16psi is alot of pressure and the hoses will stretch quite a bit and feel very hard at that pressure. If you heard a sputtering noise chances are like you said the fan motor or relay is shot because it may be trying to command the fan on but if the relay or motor has a bad spot in it, that can cause the intermittant no fan/overheat situation. I would change the relay first since it's cheap, see if it happens again, if it does throw a fan motor at it.

Hope that helps you out... glad to hear you're building pressure again

[Prospeeder]

Ok ill grab a relay, thanks, wait, wich one exactly is the relay to make it easy.

[SilentWing]

It's under your hood on the opposite side of the battery (passenger side) right in the front there should be 3 relays and I think it was the second one (the middle one) but with your car being the age it is it may have gottem moved around so your best bet would be to look at the color of the wires that go into the fan and match it up to the color of the wires that go to the relay (like say that there's a green wire going into the fan there should be a relay with a heavy gauge red wire and a green wire going into the relay)

[Prospeeder]

well the temp switch seemed to have made the fan come on earier, so well see. But now my check engine light is on for an EGR code :( 68$ for a new one isnt THAT bad for a digital egr, but im gonna try cleanin it.

[george]

Maybe you have to redo the head gaskets again. If the heads have a bad spot on the surface the exhaust can go into the coolant and overheat the motor everytime.
Just a thought.

[Prospeeder]

Nah definatly not the heads. I can drive on the hottest day with the a/c on and it stays on 210, but it just will randomly get hot, wich iv narrowed down to the fan, its just not coming on untill the car gets too hot, the A/C seems to be keeping it cool as it forces the fan on. so far so good with the new temp sensor. But ill give it a few more days.