Finally got some beautiful weather-85* and decided to cruise around town yesterday. Drove for about 20 miles. About a mile from home noticed an intermittant loud clacking from engine, but only when I got on it. Eased her into the garage and shut it down. It was then that I noticed overheating, with steam blowing out the relief tube. (No gauges just idiot lights, none that lit off).Let it cool for about 10 minutes then decided to start up and back out to hose it down. When I turned it over I heard loud clanging noise and shut it down again. Noise resembled a fan blade hitting something. Fan is free and clear. I waited a few hours refilled the radiator, removed valve covers. Lifters seem okay. Buttoned her up and started the motor. No unusual noises just idling a little rough. I'm looking for answers as to why she overheated and what kind of damage may have been done. I did free spin the water pump and had definite gurgling in the radiator so I'm 90% sure waterpump is still good. Motor is a factory stock 307, Radiator is new 4-months old.50/50 coolant and water. Sorry so long just wanted to make sure I covered everything. I want to take the car to Seattle on Saturday for the King Charlies show, so any advice would be appreciated.
Thanks, Rob

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70 Malibu 307 http://www.chevelles.com/showroom/17again.jpg

Not sure.... I would first suspect a stuck thermostat. I am not sure what the clangin noise was.

Are you sure your idiot lights work? I would change your oil as a precaution - inspect the oil for any coolant...good luck.

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Ron Cook TC Gold #1276 ___ ACES #5136
1969 300 Deluxe HTSS396 (http://www.chevelles.com/showroom/bow_tied4.jpg) The L35-325HP 396cid (http://www.chevelles.com/showroom/bow_tied3.jpg) 69 Memory Lane (http://www.chevelles.com/showroom/bow_tied.jpg) 1971 Malibu 2DR HT (http://www.chevelles.com/showroom/bow_tied_71Malibu.jpg)
CanAm Chevelle Club (http://www.canamchevelles.com) _____________"Take my advice, I'm not using it."

Do you have a fan shroud? If so it firmly attached so that it won't flop against the fan blade? Look for scrapes. Also, check all the rest of the drivetrain tin, starter heat shields, trans inspection cover, etc to be sure everything is tight.

Also, if you have an auto trans, it is always a good idea to check your trans fluid. Whenever the engine overheats for any amount of time the trans fluid can burn and clog up your filter. Been there.

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1967 Malibu
1967 Impala SS396 Conv.

"In theory, theory and practice are the same,
but in practice, theory and practice are different."

[This message has been edited by garyB (edited 05-14-2002).]

Just got home from work and will be headed out to the garage shortly. I am running a shroud and there are no scrapes on it. T-stat seems to open when engine is warmed up. I've only had the car since last August and this is the second time it has overheated. Originally thought the rad cap was bad, it was only a 7lb cap and blew out now I have a 16lb cap and it has blown http://www.chevelles.com/forum/confused.gif The idiot lights work, every time I start it cold the temp light comes on until the t-stat opens. Any other ideas on where I should be looking?

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70 Malibu 307 http://www.chevelles.com/showroom/17again.jpg

What timing are you running? What colour are the plugs? Could there be an air pocket in the block letting the coolant steam? With rad cap off, can you see the coolant flowing inside the rad? Just thinking out loud here...

I'd pull and check the water pump for sure. Run a compression check. "Clanging" noise possibly detonation? I have had experience with overheated engines sevearl times--best to not do anything except shut it down and let it cool down all the way with maybe a electric fan blowing on it to speed the process a little.

My $0.02

UPDATE: replaced thermostat, discovered "clanging" noise was coming fom muffler-Detonation? slight backfire? Checked dwell set at 30* timing was at 2*advance,brought up to 8* ensured idle at 650 rpm in drive. I don't have the proper means of checking water temp, but I did use a Raytek thermometer aimed it at the manifold near the t-stat housing and it registered 202*, top hose temp showing 185*. I'm sure these aren't too accurate but I'm trying. Went for a road test and I have a lot of detonation when I accelerate. Letting the engine cool then I'm going to pull the plugs and check them out. Any direction or advice is appreciated. By the way shouldn't the radiator return hose from the manifold be solid-(not real mushy) when the coolant is flowing?
Rob

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70 Malibu 307 http://www.chevelles.com/showroom/17again.jpg

You may have found the problem--mushy hose. The hose is probley sucking flat at speed stopping most of your water flow. Replace it with a new one.