Fluctuating temperatures while driving

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challyrtse

challyrtse

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Richland, WA
Okay, I've got a '67 Dart with a stock 318 lower end and heads, edelbrock intake, edelbrock 4-barrell, and dual exhaust.
Recently my car started running hot, on the highway or in town. Sometimes it runs at perfect temperature (from my stock gauges), but then other times it will heat up to the hot end of the gauge, or even peg it out.
Speeding up usually drops the temperature some, but then again sometimes slowing down will cause temp to turn as well.
I have replaced the thermostat (195 F), installed it the right way (spring down into the manifold), sending unit, and replaced the stock 4 blade fan with a new 6 bladed flex fan of the same size (installed the right way, evidenced by much more air flow into the engine compartment!). I even flushed out all of the old coolant and replaced it with new.
The frustrating part is that sometimes the temperature is perfect. Then out of the blue, it starts heating up quick.
Any ideas?
 
you did all the stuff i would have.......possibly radiator or head gasket..issue.....don;t just go and pull the heads...you need to air up the cylinders on tdc and remove rad cap and look for bubbles....or you could pull all 8 plugs and pressurize coolant system overnite and see if it fills up plug holes or loses pressure...only go to 15lbs or you will pop heater core/amongst other stuff I hope this helps....if you need the tools..if you pay shipping I will send you what you need to check it..of course I will need back when you are finished.....PM ME
 
Sounds like you could possibly have issues with a head gasket, thats the way they act . The best thing to do is rule out a possibility of a head gasket or crack somewhere with a combustion leak test . I always do that first at our shop if I suspect a problem there. Napa sells a kit or you could have a shop do it for you.

http://www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm
 
if you have an electrical sending unit look for bare spots that may be grounding out/if you think it might be a head gasket look for bubbles in the coolant with the car running
 
Try taking the raditor out and have a shop flow test it. They get calcium deposits in them and don't come out with flushing.
 
Thanks for the feedback, guys.
I think I will take the radiator to a shop again. I did it about 14 years ago, and recently had to re-solder the upper joint because it was leaking...
Chances are if the rad needed soldering, then it probably should be cleaned and de-limed, too.
I would like to get a shroud, I understand that they can make the car run cooler by 10-15 degrees; mine hasn't had one since I bought it, and it does get hot here in the summer.
Probably won't get time to get it into the shop for a few weeks, so if I don't post back soon, it's because I'm being worked like a rented mule (lol). Enjoy Memorial Day everyone!
 
I got a question about the gauge. Wild needle swings ? Like if you drive to town and stop for gas, when you turn the switch back on does the needle race to pegged 'H' and fall back down to around normal within a minute ?
 
RedFish said:
I got a question about the gauge. Wild needle swings ? Like if you drive to town and stop for gas, when you turn the switch back on does the needle race to pegged 'H' and fall back down to around normal within a minute ?
Click to expand...
Did you check thermostat before instalation? Have had some crappy ones lately. Check in boiling water, had one I checked a few times while out of car and would take different times to open and would intermitly open at different gaps sometimes barley open sometimes open all the way, sometimes took a long time to open. See thread titled is this head gasket? in engine issues section. Just a thought and alot cheaper and easier than head gasket. Good Luck.
 
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