overheating issue

[hamjet]

(bought 72 gmc several years ago. had a rebuilt original 307 with like 30 miles on it. has a set of 99 truck heads on it. truck sat for several years with motor covered).... I keep reading this over and over, did you drive this around for a while before you stored it or did you get it and park it for years. if thats the case, are intake gaskets wrong or maybe put on wrong? perhaps blocking the water passage to the top rad hose? just reaching...."remove the t-stat, drain the block, pour water in the top rad hose where its unhooked from the rad. and see if it comes out the bottom of the block,"

[rich67]

Originally Posted by Ironangel

Looks correct...But NEVER use Teflon tape on those sending units...They need to ground to the block to function properly...There is a conductive pipe dope that can be used that seals and conducts... I'm curious by the way to find out what the issue is with that motor of yours...I'm thinkin, bad water pump or a rats nest in the block somewhere...? Hang in there Pard, you'll figure it out!

thanx for the tip feller. actually i didnt. motor was already assemled when i bought it. but handy knowledge. there is actually about a 1/2" of threads that were in the head without tape. dont think teflon even reached threads. not sure why its on there. i didnt get to water hose the block or anything actually as the hydrant at my shop was froze. but i did blow air thru everything that i saw. wrong head gaskets. hmmm. pretty good thought. i thought about pulling a head to inspect last nite but didnt want to ruin a gasket til last resort. if they used the good ones i think they are reuseable. if not them dam things are gettin expensive! lol

[FirstOwner69]

Originally Posted by 67 cst swb

My only input would be:
Do the coolant holes line up properly?
Did they use a head gasket that blocked the holes?
But... I think your use of a garden hose and flushing the motor may have answered that...
just throwing in another thought here...
All the above thoughts I think were on track.

That's why I asked the unanswered questions in post 11. I am not an expert or mechanic so I can't vouch for the accuracy of my comment below, but it is something to consider. I may be all wet (no pun intended).

I have a GMPP 350 with Vortec heads like the 99 heads in the OP's 1st post. GMPP told me that I should run a bypass hose from the pump to the intake. The reason they gave is that the old style 350 blocks (not sure of other SBCs) have a coolant passage cast in the block up to and through the right head, but Vortec heads do not have the holes so the coolant flow is blocked and the heads aren't adequately cooled during warm up. I would also think the heated coolant may have difficulty getting to the thermostat to open it. I also have factory A/C with the heater shutoff valve so that may have entered into their recommendation.

[rich67]

Originally Posted by FirstOwner69

That's why I asked the unanswered questions in post 11. I am not an expert or mechanic so I can't vouch for the accuracy of my comment below, but it is something to consider. I may be all wet (no pun intended).

I have a GMPP 350 with Vortec heads like the 99 heads in the OP's 1st post. GMPP told me that I should run a bypass hose from the pump to the intake. The reason they gave is that the old style 350 blocks (not sure of other SBCs) have a coolant passage cast in the block up to and through the right head, but Vortec heads do not have the holes so the coolant flow is blocked and the heads aren't adequately cooled during warm up. I would also think the heated coolant may have difficulty getting to the thermostat to open it. I also have factory A/C with the heater shutoff valve so that may have entered into their recommendation.

sorry i didnt get a reply to yours the first time. i missed it. i had heard that before about the vortec heads but had forgotten about it. and was unsure if it was all years or just some. i can run a bypass hose easy enuff to try it. thank you sir.i also have factory a/c but none of the engine bay stuff has been installed yet. so that shouldnt be a factor. thanx again, rich

[rich67]

Originally Posted by hamjet

(bought 72 gmc several years ago. had a rebuilt original 307 with like 30 miles on it. has a set of 99 truck heads on it. truck sat for several years with motor covered).... I keep reading this over and over, did you drive this around for a while before you stored it or did you get it and park it for years. if thats the case, are intake gaskets wrong or maybe put on wrong? perhaps blocking the water passage to the top rad hose? just reaching...."remove the t-stat, drain the block, pour water in the top rad hose where its unhooked from the rad. and see if it comes out the bottom of the block,"

no i never ran it but previous owner did about 30 miles he said. when u say the bottom of the block you mean one of the drain plugs on the side of the block?

[FirstOwner69]

Originally Posted by rich67

no i never ran it but previous owner did about 30 miles he said. when u say the bottom of the block you mean one of the drain plugs on the side of the block?

Sorry to respond to a question to someone else, but since he's not online... I'd assume that's what he meant. Drain plugs on both sides.

[hamjet]

I just got on, no, I meant take the bottom radiator hose off and see by pouring water in where the thermostat goes and see if water comes out the bottom radiator hose. it should flow all the way to the bottom, comming out the water pump...

[hamjet]

Hi rich67, did you find out anything yet?????

[88Ironduke]

Just out of curiosity when you removed the serpentine system, what kind of pulley was on the water pump?

If it was smooth pulley that might just mean it receives the back of the belt and rotates the opposite direction of the crank shaft rotation. This would explain the failure to circulate zero coolant. The water pump look right, and be right for a serpentine system but not standard V-belts. The vanes of the water pump would be manufactured accordingly to circulate water for its respective system. Just my .02 cents.

88Ironduke

[NobleSix]

i am curious to know if you have made any progress on this issue. pretty solid thinking from the previous posters.

[swamp rat]

Unless i missed it i didn't read (speed reading maybe?) anywhere where you replaced the water pump with the correct rotation water pump, a serpentine setup uses a reverse rotation impeller inside the same housing, it will not allow the water to flow properly if you are now running V-Belts.

[bigmac73]

any new updates, I also have a vortec top end set up and i do not have a bypass hose , i drilled a couple of small 1/16 holes in my thermostat to allow air to escape and water to flow

[ARC190]

I've got a 190* thermostat as well. When I warm it up the temp climbs all the way to the mark just below the red and then drops to normal operating temp (takes about 20 seconds to drop). It's been like that since I got the truck over a year ago. Have you tried seeing if that happens, or does the temp just stay up?

[Poppa Wheelie]

If your coolant is still cold and the temp gauge is peaking, your gauge or sender or both are not working right.

Cooling systems are pretty simple. If pump, radiator, cap, and hoses are good, and you said you tested the t-stat, it has to be right. Let the motor idle with cap off, when motor warms the coolant enough, the t-stat will open, and the coolant level in the rad will fall. Re-fill the radiator and install cap. If both hoses get warm, its good.

I suspect faulty gauge and/or sender.

[Boog]

If I recall right a temp gauge uses a different sending unit than a temp light. That truck may have had a factory temp light originally and someone replaced it with a temp gauge setup. You have no way of knowing if it has the correct sending unit in it now.
Ditto on the water pump. A reverse flow pump looks just like a forward flow pump. The vanes inside are reversed however.
If you removed the upper rad hose at the rad and start it up water should push out of the open end of the hose when the thermostat opens. That's the normal direction of coolant flow on these trucks. If you have a 4 row radiator you won't notice as much coolant flow into the radiator due to the extra thickness of the radiator tanks.

[rich67]

im sorry folks ive been away from my puter for awhile.lol i just all the posts tho and was dam good reading. heres an update. first of all the serpentine pulley was smooth by the way. i replaced with new short snout factory correct water pump. i ran bypass hose and still the same. oh and mine doesnt stop climbing(heat guage) until i shut truck off. so i got disgusted and tore motor down. driver side head around number 7 cylinder was full of looked like large paint chips. had almost formed a cacoon lookin deal. so new gaskets and heads back on. intake sometime today. im guessin stuff came out of rad when it heated up. only flushed with water first time. but been cleaned with acid now. rad was used and i have a 3 core back in it now. cleaned and tried a four core to try to solve issue but it was used and leaked so back to the 3 core that doesnt. hope i responded to all posts. thanx everybody for yor knowledge! i appreciate it, rich

[OJ1988]

Did you get it back together?

[rich67]

Originally Posted by OJ1988

Did you get it back together?

I did get it all back together and it did the same thing. Got disgusted and pulled it out of the shop and have been taking a break from it. Bout have my sanity back enuff to start on it again.been busy.