time to ask the gurus. overheating.

kawdude

kawdude

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History first..... 68 newport covertible 383 2bbl 22 inch radiator. sat since 89, cooling system dry. i bought the car, lubed the cylinders, new plugs runs very well. Checked brakes, and all fluids, new oil and filter, did some repairs on floors new tires. I have flushed the radiator, flushed the block the best i can with a garden hose through the top and bottom rad hoses flushed radiator added prestone flush, ran till got warm, shut off let cool, ran till warm etc a few times, flushed all again, new hoses, new thermostat, new spring in lower hose, new water pump, new rad cap (16) tried a 7 pound cap, new heater hoses, new sunpro temp gauge, drive the car 5 miles or less, car overheats, top hose hard as a rock, pushes water out into a catch bottle i put on, when it cools down draws water back into system. i pressure tested the system tested ok, left pressure tester on warmed car up, thermostat opens, rev car pressure does not increase. water does not seem to me to move alot in the radiator after the thermostat opens. i been a mechanic most my life but im stumped on this....

Any ideas?

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Sounds like you have a hunk of dirt or other crap somewhere that's causing a blockage in the circulation, OR you are running too light of a rad cap. Is your car air conditioned, or do you have the A/C-spec water pump? What is the thermostat? 165*? 185*? You might consider running the correct water pump (the A/C and non-A/C are different internally, with the number of impeller fins being different) and run a 16# radiator cap. Try the cap first. That's where I'd go, based on what you have done, so far.
 
You've done absolutely everything possible.
This is one for Click and Clack.

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Last edited:
Ah the Tappet brothers!!!
 
I tried an old 16 pound cap,an old 7 pound cap a, new 16 pound cap, tried all of the above loose, the car is a convertible no air conditioning. put on the only water pump autozone offers. Thermostat is a 190 and new, tried it with no thermostat.....

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Possible headgasket rusted out or maybe spun bearing? My motor sat almost 20 years. Did everything thing you did and mine also ran hot. She had no oil pressure so I assumed why it ran hot. Took motor apart sure enough 2 spun bearings cracked piston and busted rings. Sadly you may be looking at same issues. Oddly ir honestly seem to run fine besides overheating! What is your oil pressure like? Mine was only 10 at idle. After rebuild sits 40+ at idle.
 
Maybe an air flow problem, Is there a shroud .....? clogged fins in the rad ......? GM fan ....? (GM fan can be bolted to the water pump but is a reverse rotation from a Mopar).
Beyond that you may need to pull the heads and check the passages for restrictions.
 
Taking these 2 facts into account:

kawdude said:
i pressure tested the system tested ok, left pressure tester on warmed car up, thermostat opens, rev car pressure does not increase. water does not seem to me to move alot in the radiator after the thermostat opens. i been a mechanic most my life but im stumped on this....
Click to expand...

kawdude said:
It will suck the lower hose flat if theres no spring in it. I thought i had it when i found that. Nope...
Click to expand...

I think the radiator is causing the problem, no flow visible with open thermostat and a new lower hose without spring that goes flat tells me the pump can't get it out of the radiator.
 
68-300 said:
Taking these 2 facts into account:

kawdude said:
i pressure tested the system tested ok, left pressure tester on warmed car up, thermostat opens, rev car pressure does not increase. water does not seem to me to move alot in the radiator after the thermostat opens. i been a mechanic most my life but im stumped on this....
Click to expand...

kawdude said:
It will suck the lower hose flat if theres no spring in it. I thought i had it when i found that. Nope...
Click to expand...

I think the radiator is causing the problem, no flow visible with open thermostat and a new lower hose without spring that goes flat tells me the pump can't get it out of the radiator.
Click to expand...

Makes sense now that you mention it. Think of a thick milkshake trying to get it through the straw. I guess i didnt think that cuz water flows through it seemingly well when i put the garden hose to it. I have another radiator think ill try that one today.

Posted via Topify on Android
 
I would try radiator first but may very well be a head gasket those steel shim gaskets take a beating with a dry system get a couple of pits heading toward the cylinder and it doesn't take much the rock hard hose before it gets hot is a telltale sign.
 
I'm very mechanically challenged so take this with a huge grain of salt. I've heard from guys that have done major work on engines i.e. head removal or rebuilds that upon start up they overheat. The culprit turned out to be air in the system. Just wondering if flushing with a hose puts air in the system. Not sure how to expel it though.
 
(GM fan can be bolted to the water pump but is a reverse rotation from a Mopar)



commando1 said:
You are un - frikkan - believable.....
Click to expand...

True story ........ I found that condition once. After a lot of head scratching. (Actually it was a ford fan on a Chevy corvette), but the symptons were the same. Figured it out while standing in front of the car with the engine running ...... Air was blowing OUT of the grille.
 
kawdude said:
Makes sense now that you mention it. Think of a thick milkshake trying to get it through the straw. I guess i didnt think that cuz water flows through it seemingly well when i put the garden hose to it. I have another radiator think ill try that one today.
Click to expand...

A quick way to check rad flow rate is to fill the rad, then disconnect the lower hose from the rad. Water should gush out. If it just flows at a slower rare the rods have a restrictive build up in them.
 
Had a friend in the Navy put a buick 231 in a vega then used the fan from 4 cylinder, never noticed 'cept the overheating as soon as you would drive and to make things worse was the hood opened backwards so you never stood in front of grill found it one day I was revving engine he walked by grill with shorts on, ding light bulb moment, new fan problem solved.
 
Hose dont get hard till thermostat opens...

Ran and revved engine with pressure tester on and thermostat open did not gain pressure..

Fan is correct. sucking....

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