at my wits end !!!!!!!!!!!!!!!!!

ok heres the scoop.....
i have a very big dilemma and i am at my wits end.
My 1971 mav grabber with 302v8 it keeps overheating.
i have bought a new water pump,thermostat x 3, new radiator, new hoses upper and lower,flushed the engine many times, have bought an electric fan for auxilary,and even put the 28 below new style antifreeze, put a pressure tester on it and no leaks......
please let me know what can i do.... i've never even considered selling it untill now. please help me before i can't take anymore. i love my baby. thanx for any advice . ~dan~

 

Do you have a fan shroud? Seems like that is the only thing you haven't tried. Also, are you sure you don't have a bad head gasket or so? I had to have an emmision tester put the tailpipe probe into the overflow canister of my Mav, and check for combustion gas. Sure enough, bad gasket. Give it a try.

Earl

 

hot & bothered

So ubder what situations does it over heat? Stop & go, rush hour traffic in Phoenix on a 110 deg day? Just driving down the road? All the time? How old is the engine? Any mods to it?

 

I lean towards Mr. Branham's fan shroud comment.
Is the radiator cap good. If it doesn't hold enough pressure it will overheat.
Another thing that might be considered is overbore on the block. Did the problem start out of the blue, or was it after a re-build? SBF blocks can go as high as .040" or .060" over on the bore, but the block loses some cooling ability. Depending on core shift it could lose enough cooling ability to make it nearly impossible to keep streetable.
Next thing I noted, you say that there are no leaks under pressure. Did you bring the gauge on the tester up to cap pressure and let it sit for a couple minutes and see if the pressure stayed up or went down? If it went down, then you could have a leak in the system that is internal.
Just some ideas.
Dave

 

hot time tonight

Well now here is some of the ways most people never look at that can make it also over heat.
To small of drive pulley on the crank.
Plugged exhaust system or to restrictive for the engine.
Rust plugging up the water jackets, maybe even some old core plugs inside, flushing won't get this out either.
Radiator to small. One row,
HiPo engine with a LowPo cooling system.
Restricted air flow into radiator area.
To small of vanes in the water pump.

 

What mixture of Antifreeze and water are you using? I have a hunch that you are running almost 100% antifreeze. That'll make you overheat.

 

on a hunch

last night after alot of thought i drained all my antifreeze.
when it got to the bottom.......i noticed that all the cores were stopped up. it has a brand new radiator cap (13lbs) 50\50 antifreeze and water, no performance mods except intake and carb, stock air flow ( even took off the ac unit and condenser,) it would only happen every once in awhile. going down the road at 60 mph or sometimes when i would stop at a light. it did good there for awhile but now i'm pretty sure thats my problem, a stopped up new radiator. today i am going to pull the drain plugs and flush the system that way...hoping the rust and sediment will come out..and as for the radiator i am getting a new one....and it was a 3 core. thanx for all comments. keep em coming and thanx for all the help. ~Dan~

 

oh almost forgot.....

it does have a fan shroud, and has a 3 inch exhaust with flowmaster straight back so it's not restricted. the pressure tester stayed the same under 17lbs after 10 mins. thanx for all the help. ya'll are friends ..~dan~

 

plugged system

sounds like you have lots of rust in the block breaking loose and ending up in the radiator. You might consider pulling all the core plugs out of the block and running some thru the system. Or just pull the back two, one at a time, and run water thru it to back flush the system. It might not be much fun to do, but overheating ain't no fun either.

 

when i first bought my 64 fairlane it would overheat at an idle or over 50mph. anywhere in between it was just fine. took the radiator to a shop and had it cleaned out. cured the problem.

 

Hot under ze collar?

BlackMav,

I agree with everyone here, especially Ratio411 with his comment about a bad radiator cap.

I had this same problem on "Pegasus" after putting in a CHP 302 V8. It would overheat pretty quickly. After swapping out a new radiator, hoses and floshing the system, absolutely no change! It still overheated!

In filling the radiator after the nth time, letting the engine cool, I re-checked the water level and you couldn't even see it in the radiator (no leaks though). An additional 2 quarts was needed to top it back off. After this, it was still running hot, but not as hot as it had been.

After considering driving it into the nearest pond in frustration, I checked the radiator cap and noticed that the 25+ year old cap had cracks, etc on the little rubber gasket. Figuring "what the heck", I went and bought a new Stant radiator cap...

Whoalla! The engine now purrs along at 190 degrees all day long regardless of the outside temp. Apparently the old cap couldn't hold the pressure and and effectively lowered the boiling point of the antifreeze/water mixture (higher pressure=higher boiling point).

All of this after over $200 in other parts just to find out it was a $6.00 radiator cap! Now that has to put me in the idiot's club in a hurry! (and maybe the time I tried to pull out of my garage with the hood up, but I won't mention anything about that!!!)

Some other things to check... Tranny fluid! If the fluid level is low then the torque converter will get hotter than hell and transfer that heat to the block.

Also... A bad (new) water pump! I bought four defective pumps from AutoZone before I gave up on them and got one from the local O'reilly store that worked! I don't buy anything from AutoZone anymore! Seems the vanes on the supposedly "new" pumps were simply spinning on the shafts! ALWAYS check that new pump before ya put it on!

Hope some of these suggestions helps!

Good luck and keep us posted
Tracy

 

I don't know if you changed your rear gear, but I noticed that when I changed my rear gear ratio to 4.11, I couldn't cruise at such a high speed for a period of time or the temp gauge would climb. 4,000 rpm was the max to go on the highway or it would overheat.

 

Comment about water pumps from Auto Zone. Look at what you are getting before you leave the store. The cheapos are stamp steel impellers and have no backs on them. The good ones are cast iron with the backing like the factory units.

 

yet another push on flushing the block good.
my 74 sat off and on, the previous owner didn't drive it much.
The owner before that was an old man, he drove it on weekends.
Kept it in a barn.
the block is nasty, I've flushed it often... its run down to I keep it under 3000rpms on the highway until I get my new engine in there.
Nothing short of dipping the block is getting this crap out of there, its too hard.
Mine is so far gone I can't see any way to clean it without disassembling the engine.
alot of it looks like aluminum corrosion, until I got it the only aluminum part was the T-stat housing.
letting a car sit is bad, mmkay?

 

Re: Hot under ze collar?

LOL! but you DID mention it!

Tracy! I'm gonna point and laugh at you the next time I see you! LOL!

And when I do see you again, I'll avoid telling you about the time I set some guy's truck on fire by obliging him when he asked,

"I can't tell how much gas I've got in here. You got a light?"

So I pulled out my trusty Zippo, put it about 3 feet away from the spout (what "I" thought was far enough away) and struck the flint.




Damn that was a nice truck!


(we ALL have 'stoopid' stories )

(and 'sorry bout getting off topic).