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Overheating, HELP!

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Posted by: StangRuner50

I just bought my first mark viii, and Im on my last nerve already. the car has been overhearting since I got it. However it stays in th middle of the heating range for about the first 3-4 miles of driving, and then it starts to climb. Ive replaced the thermostat and the degas cap. Ive also added a bottle of purple ice. I jut double checked to make sure I burped the system completely and all was well. if you let the heat run for about 3 minutes, it cools down when you shut it back off, but then goes right back up. Theres no water in the oil. fan is running. and I dont see any kind of sepage out of the whole on he water pump. I dont know what to do next aside from drive this damn car into a lake. any help would be greatly appreciated. Ive been reading alot of post on here about some of the overheating issues with these cars and there seems to be a lot of them. Only thing I can think left to do is change out the degas bottle, but wanted to see if you guys had any ideas first. Thanks. Shawn

Posted by: StangRuner50

also, ac started blowing hot air, so I went to charge it today its reading 150 psi! any ideas?

Posted by: Calabrio

Are you absolutely positive that you got a perfect seal on the thermostat housing? It's sometimes a tricky thing to get that thermostat and gasket seated correctly.

First thing I'd recommend is looking under the car for any indication of a coolant leak, even a tiny one.

Is the radiator leaking? A common place for failure is where the aluminum is pressed into the plastic tank.

Is the thermostat housing leaking? As mentioned, it's rough to get a perfect seal? I used thermostat housing sealant to insure it?

Is there an oil leak? The oil filter adapter gasket can fail. Not only does it permit oil to leak, but it sucks air into the cooling system.

And, burp the system again. Sometimes it take repeated attempts to get all the air out. And while it's running with the cross over tube open, bounce the car up and down to shake loose air bubbles.

And finally, is the fan turning on? Does the radiator fan turn on? Does it turn on when you turn the A/C on? If not, that'll cause the car to run hot.

Posted by: 93' Blue on blue

I hear our cars can be tricky to bleed. When you changed the thermostat did you fill and bleed at the cross over tube? If it were me i would try bleeding again, ignition on with heater set to max. If still no joy would re check these things: radiator for obstructions, thermostat function, all hoses, water pump belt tension, fans. Failing those then maybe a coolant pressure test and or coolant drain/flush. Hope these suggestions help.

Posted by: StangRuner50

thanks for the suggestions guys. The guy I bought the car from said he just put a new radiator in, and it does look pretty new, as well as all of the hoses. Yes I did fill from the cross over tube. I think im going to take the new thermostat out and make sure its working. Do you RVT to seal the housing? and what do you do just run a bead around the o-ring. Im a 5.0 guy, this whole 4.6 thing is giving me a headache. Thanks for the help guys.

Posted by: unity

I will repeat 93, did you burp the system? You dont just fill it as the crossover tube, you fill, run, fill, run, rock the car, fill, run, etc.... until no air EVER comes back into that tube!

Posted by: StangRuner50

when I burped it I let it run for about 10 mins with the heater on 90. when coolant came out, I closed it off, and shut off the car. Ill try the bounce technique and see if it works

Posted by: turborich

About the A/C, You said 150 PSI. Is that on the low side or the high side? With the compressor on or off? Your low side should be around 35-45 psi and the high side will varry but 250-350 PSI is about normal. This is with the car running and A/C turned on MAX. Your radiator fan should be on as well.

My 95 Mark didn't overheat however it did run very hot all last summer. Around 230-240 degrees. It really ran hot on the freeway. I tried it all! Towards the end of summer when it was cooling down I installed a plate type trans cooler and a air dam which had been missing. This summer in the 115+ heat it has been running nice and cool! I think the air dam helped out alot.

My friends 94 however also ran hot. it has a air dam and we installed a tranny cooler. It still runs towards the top of the gauge. 230 degrees or so. Go figure???

It seems that some of these cars run cool and some run warm. By the way, I tried the 40 below stuff in my buddys car per instructions. It made no difference! JUNK! I am running about 40% antifreeze & 60% distilled water in my car.

Posted by: unity

Quote:

Originally Posted by StangRuner50

when I burped it I let it run for about 10 mins with the heater on 90. when coolant came out, I closed it off, and shut off the car. Ill try the bounce technique and see if it works

This is NOT a 1970's Chevy.

Turning the heat on while trying to burp the air out does nothing. The Mark VIII uses a continuous flow heater core, its ALWAYS hot and nothing obstructs the flow of water, unlike older cars that often had a vacuum valve that opened.

This is what you do. You open it up when the engine is cool. Rock the car really good so the coolant drops down. Add more coolant and rock some more. Once you have done this you will reach a point where no more will go in. Put the cap on and tighten a bit. Now start up it and run it for maybe 10 seconds. DO NOT REV IT, NEVER REV IT WITH LOW COOLANT - it will create foam, foam is deadly. After running it repeat above, add, rock, fill, rock, fill, etc.. then run again. Just keep repeating til you have no more air to escape. I also rake mine off roading to make sure any air pockets at the backs of the heads gets free. I then let it cool and fill if needed.

In short, air in the crossover tube will prohibit the flow of coolant. When this happens coolant does not flow through the engine AT ALL.

Im gonna be blunt: At the method and rate you are heating yours up your on you way to needing a new engine. This is an aluminum block and it does not take much to warp and destroy it. One over-heat is enough to do damage.

Posted by: Roadboss

All you need is to have a clean surface and use only the "O" ring. I'd make sure you have the correct thermostat and installed right as well. One other thing that I would mention is that there is quite a bit of differenceces in temp readings from car to car (probably due to temp sensor variations). Some of our cars will show 2 whole letters difference at operating temps.

Posted by: turborich

Quote:

Originally Posted by Roadboss

All you need is to have a clean surface and use only the "O" ring. I'd make sure you have the correct thermostat and installed right as well. One other thing that I would mention is that there is quite a bit of differenceces in temp readings from car to car (probably due to temp sensor variations). Some of our cars will show 2 whole letters difference at operating temps.

Without going by the letters on the gauge, What temp should a Mark VIII run at if properly maintained and in good mechanical condition with the factory T-Stat? Around 210 Degrees or so??? Or am I way off?

Posted by: mespock

Did you out the T-Stat in, in the right direction?

Posted by: JoeyLincolnMK8

rock the car??? unity,what do you mean by this? I do not know that term, nor ever heard it used before. can you explain please?

Posted by: unity

Quote:

Originally Posted by JoeyLincolnMK8

rock the car??? unity,what do you mean by this? I do not know that term, nor ever heard it used before. can you explain please?

Definitions of rock on the Web:

a lump or mass of hard consolidated mineral matter; "he threw a rock at me"
material consisting of the aggregate of minerals like those making up the Earth's crust; "that mountain is solid rock"; "stone is abundant in New England and there are many quarries"
United States gynecologist and devout Catholic who conducted the first clinical trials of the oral contraceptive pill (1890-1984)
(figurative) someone who is strong and stable and dependable; "he was her rock during the crisis"; "Thou art Peter, and upon this rock I will build my church"--Gospel According to Matthew
rock candy: hard bright-colored stick candy (typically flavored with peppermint)
move back and forth or sideways; "the ship was rocking"; "the tall building swayed"; "She rocked back and forth on her feet"
rock 'n' roll: a genre of popular music originating in the 1950s; a blend of Black rhythm-and-blues with White country-and-western; "rock is a generic term for the range of styles that evolved out of rock'n'roll."
pitching dangerously to one side
cause to move back and forth; "rock the cradle"; "rock the baby"; "the wind swayed the trees gently"

Posted by: Roadboss

It should run about 10-20 degrees higher than thermo stat. The Mark Vlll stock system is very efficient which is also demonstrated by the fact that the fan actually turns off when up to cruise speed. The fan itself has one of the larger CFM specs as well. Without getting into letters NORMAL is normal, just as long as the pointer stays in side of it and reacts accordingly, adleast this is my observation and a few years of experience.

Posted by: unity

Im going to add that you can not compare the Gen II reading to a Gen I. The Gen I is "real" where as the Gen II is "calibrated" and controlled by the computer at all times.

Posted by: JoeyLincolnMK8

Quote:

Originally Posted by unity

well... i guess you need two people to rock the car. one person pushing down on the rear and another person to push down on the front. makes a lot of sense to me! thanks

Posted by: StangRuner50

unity, why is foam deadly? It is my understanding through research that it is normal in a case where there is air in the coolant system. my car has been spitting out foam when I try to burp the system? please enlighten me on this. Now Im having a bigger problem as the car wont start. Im going to start another post on that though.. Thanks for the help guys.

Posted by: StangRuner50

oh, and turborich, its reading 150 on the low side with car on and ac at 60degrees

Posted by: unity

Foam is just as bad as air but is also super-heated coolant that can travel and therefore can get into palaces that air may escape from, such as around the water pump. Really foam is a sign that there is major air in the system, not just in the crossover tube. Also foamed coolant can start to break down into a more "pure" form and gun up the hoses and water pump but that usually happens if you have pure anti-freeze in there with no water blend.

Posted by: rmac694203

The PSI should not get that high. The high pressure switch should kick the compressor off if it gets that high.

Posted by: StangRuner50

I dont unerstand why it would get that high in the first place. low side is the fitting on the fire wall right

Posted by: Psychostang

Low side is on the accumulator. If your readings are correct, then you have a restriction in the system. Your Overpressure switch is shutting down the system.

Posted by: turborich

I would guess a failing compressor or a clogged orifice tube. 150 is WAY TO HIGH! Perhaps it is also way overcharged. What does the high side read?

if you dont have a decent set of gauges one can be picked up from harbor freight tools for around $35-$40 on sale.

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