Hey guys/gals. I'm desperate here. All I know is to tell you what's been going on and see what you guys come up with. Like the title says this is a little lengthy. Car is in my sig... ~135k miles with NO overheating issues in the past.

~2 months ago - coolant leaking from weep-hole on bottom of water pump, never ran hot. replaced with new OEM model, no problems (ie leaks, overheating)

~1 month ago - small (1/2"), vertical crack in pass side rad end cap (starting ~1" below heater hose connection. not running hot

~1.5 weeks ago - crack had grown enough to get me weird looks from fellow drivers concerned that my car was on fire (steam) Still drove her as she still wasn't running hot, nor was the crack low enough to lose too much fluid (I topped it off as needed) and because, unfortunately, shes my only mode of transportation to/fro work.

1 week ago (Saturday) - I flushed the coolant system x 3 (warmed up, cooled off, ran with heat on, repeated etc). 3rd time the draining fluid was clean/clear enough to drink (figuratively). I replaced the radiator with a new OEM, aluminum model, put in a new 190* stat (and new gasket) as it has been down in the 20's here, lately. filled with water, warmed her up, checked for leaks, drained, filled with 50/50, ran until warm while parked on hill with nose elevated and rad cap off for air to get out of system, topped off coolant. On test drive, no overheating or leaks.

~2 days later (Monday drive to work which is ~20 mins at 50-70mph and 35* out) - temp gauge got up to bottom of redline (~245*) while moving steady at ~55mph. when i slowed to pull over, the temp dropped below 220*. I left her running as she was no longer hot. the upper rad hose was narrowed (not 'collapsed' but almost). gave her throttle, and the hose stiffened up. coolant level fine, no leaks/puddles, no white smoke from exhaust. cooled down drove off.

throughout the week (temp in the 20*'s to 40*'s) she spiratically will get blistering hot while moving and will generally cool off when slowing/stopped. OEM style, single-electric fan is working fine. i even run with AC in ON position (this turns the fan on at any engine temp... compressor is gone) to make sure the air moves ALL the time. I felt of the rad cap when she overheated once, it was ice cold, then felt the radiator... IT WAS TOO! I assume this means the coolant isn't moving from engine to rad to engine...

Friday night (~40* out) - cruising home at a steady 60mph, she maxed out the temp gauge again. I was PO'd/tired of dealing with it. My socket set was in the pass seat. I removed the thermostat on the side of the road, i was thinking the stat wasn't opening. Now we're running straight through. I know this may cause overheating as the coolant doesn't have time to cool down before exiting the radiator. BUT it's 40* and what could it hurt, shes running hot anyway... I figured it was worth a shot.

She ran warmer than usual (~220*) for the next 10 mins, but didn't overheat. the next five minutes, she would go up to 250*'s and quickly back down when I would pull over.

NOW I'm completely lost. I can't find any info other than 'check for debris in grill', 'check that air dam is still there'. The thing is... everything checks out!...:

i can see great water flow coming from heater core when the rad cap is off, when warm the upper and lower hoses are hard as rocks (with the one-time above-mentioned exception), belt's not slipping around WP pulley(as far as i can see/hear).

According to my scientic evaluation (pot of water on stove and a meat thermometer, lol, 'scientific') of the 190* stat, it is opening and closing correctly.

What should I do or look for? Thanks for your time and thanks in advance for your help. BTW I have a 16lb rad cap with a 'pressure-release' lever, if it matters.

 

wow.... that was very detailed and very helpful haha well the only thing i would say after all that would be to replace the upper and lower hoses because u said it narrowed almost flattened out.... i know u said its stiffins up but u never know when ur driving ya know.... and two double check oil dipstick and under the oil cap make sure its not a blown head gasket also u can pull out ur spark plugs if coolant leaks out for sure head gasket lol but thats very rare also check spark plugs for tint of green obviously shows sighn of anitfreeze meaning headgasket.... also look to see if there are any leaks around intake manifold and water pump etc..... other than that i have no idea my car basically does that except i have a few leaks here and there and it bugs... oh and FYI its a myth that not having your thermostat in can cause over heating thats a bull $h!+ well thing to look for hope it helps and please let us know what it is if u figure it out

 

Thanks for your input/help. Ironically I went out to check my oil earlier this AM, and topped her off. the bottom of my 710 cap had something that looked like a light tan (almost white) goop stuck to it. its consistancy reminded me of lotion, lol. it has no smell other than oil. this tells me there is coolant in my oil, right? dip stick shows no creamy/milky oil.

I made a few calls to some car friends. I thought that a blown head gasket or head, would be noticable while driving. they think that with the low compression of the LO3 it may not make a noticable miss or difference. does that sound factual (makes sense to me)? they and I were suprised that my oil level was not increasing, as coolant would add volume to crankcase. also, i havent seen signs of oil in the coolant.

I didnt think to pull any spark plugs. i will do this, but i probably will only be able to get 1, maybe 2, out of the pass side without getting under her which i dont have time to do. I did look for anything obvious (ie water marks running down the block or heads). The only thing I saw was a small leak (looks like oil only) at the center of the front lifter valley 'deck' (between the intake and block). when asked, my friends said that I could even have a leak at the intake manifold gasket which could drip into the lifter valley.

my question now is:
How would this leak or any other (assuming its small enough not to cause a miss or white smoke from exhaust) cause this much overheating?

fyi: i will be replacing rad hoses tomorrow after work.

THANKS!

 

I think you can buy a kit to test for the presence of combustion gases in the coolant-you draw a sample from
the radiator and test it,changes color or something if
combustion gases are present in the coolant.
Scum under the oil cap might only be plugged pcv valve or
something.cracked head is unlikely unless engine has been
boiled dry. As far as the overheating all i can think of is the
lower hose sucking flat when water pump turning at above
idle speeds-should be able to check this by revving the
engine while observing the lower hose.
good luck!

 

yeah and i would defiantly change the oil when u drain it you can for sure find out if its a head gasket but i dont think thats your case..... and u would be surprise how the smallest leak can affect things under high pressure a little leak can become a huge leak (ive experienced it ahah)... also check your idle if it is real low it can cause overheating at idle simply because your water pump isnt pushing enough coolant i doubt thats your problem because u said it happens while driving but thats all i have for u if all fails then i honestly dont know what to tell you but if u figure it out PLEASE let me know haha

 

actually i have one more thing check EGR valve if it goes it can cause over heating and a spark knock....

 

Locate your temp. sending unit for the gauge. Make sure the wire isn't touching anything it shouldn't be (grounding the wire pegs the gauge). Unplug the green wire at the sender, gauge should read zero. Ground the green wire, gauge should peg. If yes, gauge works.

If you have a multimeter, you could measure resistance to verify functionality of temp. sender. At full hot, gauge should be closer to 55 ohms. Upwards of 1400 ohms cold.

Make sure the temp your seeing is actually the temp it's running.

 

Couple of ideas here. first well most likely it sounds like a head gasket to me. Next i noticed you flushed the cooling system with water first and then drained the cooling system and refilled it with the 50/50 mix a a few days befor this all started. How did you drain out all the water? I ask because if you drain out the water through the drain in the radiator the block will still be full of a ton of pure water so adding a 50/50 mix after draining most of the water out minus what was in the block would still leave you with a mixture of mostly water. However its plausable that even a small leak may cause a big problem with over heating. You see if you have a leak the coolent system would instead of sucking coolent from the overflow tank would suck in air instead. So even though the overflow tank says its full there may be air in the block. What amplifies this problem 100 times is that air dosnt transfer heat well so your gauge may read a cool or normal temp untill hot coolent actually makes contact with the sensor itself then you would get a huge spike in temperature (the actual reading). Now its interesting that you meantioned you had all these leaks and cracks developing in a short period of time as well as now possably a blown head gasket or intake manifold this seems very odd to me. It may be possable you have a bad radiator cap not allowing your cooling system to relieve pressure as the car heats up (causeing blown gaskets hoses exc). Another issue with too much pressure is basically the way a cooling system works is there under pressure to increase the boiling point of the coolent by allowing the coolent to absorb more heat energy befor the coolent will change in temperature. If the pressure was too great it would allow the cooling system to absorb huge amounts of heat energy potentially more than the cooling system can cool in a reasonable amount of time. So by the time your coolent system can bring the temp under control its way overshot the max operating temp. Something to think about.

 

I'm in your same shoes man, it will overheat after 40 minutes of driving. Try getting a block test and a pressure test at the local autozone. the block tester has instructions, and the pressure test doesnt. Hook up the cap to the rad and take out your fuel pump fuse so it cant start. pump 15-18 psi into your cooling system and turn the car over a few times. if it drops pressure that means you have a leak somewhere. The only thing i havent tried with my car is to change the water pump hose. But ive seen a silky texture at the top of my overflow so i know something is up.. im taking it to my mechanics shop sunday.. good luck

 

You most likely blew a head gasket by driving your car with a coolant leak. The cooling system relies on pressure to not only raise the boiling point of the coolant but to also keep the water moving. With a leak, no pressure is built in the system and isolated hot spots occur in the dead-end water passages in the rear of the heads. With no pressure and no flow the coolant boils where it is in contact with the head. The resulting air provides almost no heat transfer and this problem compounds. The head or block expands unevenly from the intense heat and the head gasket is blown. Pull the heads and have them checked for flattness and make sure the block is still flat or you will blow new head gaskets immediately. And use new head bolts too.

 

I know this is going to sound stupid and you've probably already checked - but is your radiator fan coming on? Both my '92 formula and my '78 redbird esprit had a problem where the radiator fan wouldn't come on and they overheated too. You have to check the relay and may even need to hotwire it if it won't come on. I doubt that's the problem because it overheats while driving, but if it is it's a quick fix

 

if it overheats while driving check your airdamn under car sounds like no airflow or something stuck between your rad/cond