Car is overheating. Very strange problem and need help! - SRT Forums

HexenLord · 11-06-2009, 07:34 AM

I've been fighting with this car for about 3 months now on and off, so I'll try to start from the beginning.

About 3 months ago the car started to overheat in traffic on my way to work. Coolant boiling out of the overflow and steam going everywhere. No leaks anywhere other than the coolant spewing from the bottle.

Changed the thermostat and refilled it, didn't help. Make sure the fans kick on properly, yep.

Popped off the upper and lower radiator hoses, stuck a water hose in the upper hose and it flowed just fine out the bottom, no backup or loss of flow. Felt it for cold spots once the car warmed up, nothing.

Decided to change the water pump. Got a new one from Autozone with grease and a new timing belt. Changed everything. Acted slightly better, but was still slowly overheating. Thermostat stuck open and put in a new one, no help.

Afterwards my temperature gauge acted oddly. It would slowly rise when the car started to warm up, and then shoot to 260 before falling back to 200, up to 230, down to 0 (where it would sometimes stay for ~5 minutes), back up to 200, back to 260.. etc, and somtimes all within a matter of a couple of minutes. Compression test showed slightly low and un-even numbers. I pulled the head, had it resurfaced and put in a new headgasket with plenty of copper gasket spray on top and bottom. Also replaced: Radiator cap, thermostat housing gasket, intake manifold gasket, coolant temperature sensor, yet another new thermostat, and several other unrelated gaskets. Got it back together, car fired right up and compression test numbers were healthy.

The car still overheats. I remembered a few times I would flip the heat on and steam would come out of the vents or I would see water dripping from the AC drain below the overflow bottle after I hadn't used the AC at all, so I bypassed the heater core. Looped the lines with a U-joint and some barb fittings right at the firewall and then put a piece of hose over the openings on the firewall to keep coolant from leaking out and dirt from getting in.

Now it gets strange. The car still overheats. It never really FULLY overheats. It gets up to about ~245 and lingers. Sometimes it'll get up to the very top but it never stays for long. Also, being stopped at a light or moving at speed seems to have ZERO effect on the heat at which its running. I think I figured out the temperature gauge via a short in the wiring where the car previously had Megasquirt hooked up to it. It no longer bounces. When I take turns at speed it will float around, sometimes dropping to 230 and then up to 260 before settling at 245 again.

And it gets even more strange. Last night I took it to work in the first time I've ever REALLY driven it since the headgasket was replaced. Began overheating on my way to work but never got quite above 240. When I shut the car off at work, there was no bubbling of coolant. No coolant smell, no hissing or sizzling anywhere, just a normal shut-down. On the way home is when I got really confused. I pulled off onto an open rode and gave it a little throttle getting up to speed. The temperature gauge dropped from 250 to 230. So I brake boosted it. At just a tick over 2100 RPM I boosted it up to ~18 PSI (without increased engine RPM), and the temperature gauge plummeted to ~190 degrees and stayed there until I let off of the brake/throttle, where it immediately returned to 250*.

Does anyone have any ideas? It has a new headgasket, thermostat, thermostat housing gasket, radiator cap, water pump, its full of coolant, the radiator doesn't seem to be plugged, and the heater core is bypassed. It still overheats and when I brake boosted it, the temperature actually returned to normal.

Not looking for the uneducated or uninformed to start throwing out random guesses, I'm looking for someone who might really KNOW what they're talking about. I'm suspecting a cracked head or block, but the absence of bubbling coolant and the temp dropping 60 degrees within 3 seconds as I brake boost has me baffled.

srt-sparkle · 11-06-2009, 08:30 AM

I read everything you posted. But out of everything i didnt hear you mention once that you bled the system properly after doing all that work to the car. So perhaps maybe air is still trapped in the system.

And furthermore which type of coolant are you using I hope its not the green kind. The green kind isnt supposed to be for our cars you need to use the orange kind.

HexenLord · 11-06-2009, 09:02 AM

Coolant system was bled after the headgasket was replaced.

Going to exploit all possible options before tearing the motor apart yet again. I'll send it somewhere to have it backwashed (coolant flushed through the system in the reverse direction it normally flows) and then refilled/bled again. If that doesn't work the radiator will come out.... and if that doesn't work the head comes off.

Will be using a Felpro headgasket and swapping cams while I'm in there this time. Will NOT do this a 3rd time.

Agent_Smith81 · 11-06-2009, 09:16 AM

If it doesnt fully overheat, its possible the radiator could be plugged since its just running hot, you replaced the temp sensor and the thermostat like 3 times, the systems gotta be plugged somewhere, Im a tech and Im pulling my hair out on this one.....I know the feeling of spending alot of time and money and not fixing the problem, did u try bringing it to the dealer?

Agent_Smith81 · 11-06-2009, 09:17 AM

and where there any pieces missing from the old radiator cap?

lil_hub_cap · 11-06-2009, 01:50 PM

Quote: Originally Posted by Agent_Smith81

If it doesnt fully overheat, its possible the radiator could be plugged since its just running hot, you replaced the temp sensor and the thermostat like 3 times, the systems gotta be plugged somewhere, Im a tech and Im pulling my hair out on this one.....I know the feeling of spending alot of time and money and not fixing the problem, did u try bringing it to the dealer?

i got to agree, this is really weird. the only thing i can figure is a bad radiator as well.
what kind of coolant are you using?
I just cant see it being a cracked head, if that were the case, youd have a pretty big mess on your hands after driving the car around..

diznan88 · 11-06-2009, 01:59 PM

This might sound dumb but did u check the front of the radiator for a bag or anything. Odd that when u brake boost the temp goes down. Very odd.

Agent_Smith81 · 11-06-2009, 02:26 PM

It would be catastrophic if u had a cracked head.

AllBoost · 11-06-2009, 03:04 PM

well make sure you are using the correct fluid. when you changed the thermostat and the gasket around it make sure it sits flush with the surface and that it the little protrusion fits into the key into the thermostat housing. could of had a piece of the old one which gets brittle and breaks easily clogging up your system. also dont forget that you could have a clog towards the very bottom of the radiator. i would say taking it out and giving it a good backwards cleaning or trying to do it in the car if you have a very small hose would be the last thing on my mind. if it was a cracked head you would smell coolant and tha car would run like shit and have a huge mess. maybe you have some corrosion from the any green coolant inside the block because the green coolant is made for aluminum blocks i believe and not cast iron. (could have that backwards) but either way we have a a aluminum head and cast block so that could be a problem.

HexenLord · 11-06-2009, 04:21 PM

Thermostat and thermostat housing gaskets were in perfect shape when removed. The radiator cap wasn't missing any pieces of the seal, either.

The radiator flowed water just fine when I tested it with a hose. No backup coming out of the top like it may have been clogged, it would drain water out of the bottom just as fast as I could put it in.

As for it running bad with a cracked head... it runs fine. Still makes lots of boost, no missfire, no smell of coolant, no erradic idle.

Agent_Smith81 · 11-06-2009, 04:30 PM

I'd just try the mopar coolant and see if it makes a difference, seems like there's no mechanical problem, see if that changes the temp readings.

BLKDOUTSRT4 · 11-06-2009, 04:32 PM

what you describe sounds like intermittent fans ....they are 2 speed just cause they kick on doesnt mean they are in high speed....check and make sure they stay operational at idle ...they might be going in and out...also go to autozone and get a infared heat gun its like 20 bucks then point it across the radiator at different points and make sure heat is distributed evenly across the radiator.....if not take it off and flush it with a garden hose for about a hr....the constant flow of water will erode any buildup....and do yourself a favor ditch the mopar red coolant....i use the vw pink stuff....very very good something else to keep in mind is making sure the system achieves pressure...the cap must be good water under pressure has a higher boiling point so therefore no pressure water boils and u lose coolant....evaporation.....rad cap is the simplest and most overlooked part of cooling system

Agent_Smith81 · 11-06-2009, 04:36 PM

true.....intermittant fans will make the car run hot and send that needle up.

Billyboy1209 · 11-06-2009, 04:43 PM

dude im having the same problem no joke. Iv tried everything i hope you find out whats wrong.

BLKDOUTSRT4 · 11-06-2009, 04:48 PM

worst case is vanes from back of the water pump separated keeping coolant from flowing...ive seen this happen before but not to this style of pump i hope you replaced the pump when you did the head gasket...if not you are going to be my new example of why timing belt driven water pumps need to be replaced every single time the belt comes off....