Overheating = heater valve. I had no vaccum to the heater valve, which it turn was always pumping it to the heater core and cutting it off from the other path it goes...oil cooler and radiator?

i knew it was going to be something insignificant

I just ran my washer fluid vac line to it to keep a constang vaccum on it and it runs great now. 190 as of now but i dont have a thermo in there, gotta get 1 in to repressurize the system and well see what the temps are after that.

 

reminds me of when i first got mine the stereo didn't work so i took the whole thing apart and checked all the wiring, then two weeks later checked the blown fuse good to hear you finally figured it out

 

Um, no.

The heater core bypass valve just bypasses the heater core. At worst you'll be running coolant into the heater core. They both come out the same way. Just follow the lines. There's a T junction down on the frame rail where the lines merge. It runs back to the radiator on the hot side and back down the tank into the water pump and through the engine again.

 

ah but what if there was a blockage in the heater core?

 

even if the core was completely blocked the car was still pumping coolant thru the radiator...

 

Yep, in the water pump, out the water neck (thermostat).

On older cars the heater core didn't dump into the radiator hot side, it dumped back into the water pump.

 

yup still overheats..guess it was just because it was cold. Ok then im really stumped...but just out of curiousity..which way should the fans be spinning?

 

counter clockwise if u were standing in front of them looking towards the front of the car

 

ok yea they are spinning the right way...dammit

im at my wits end..i can not figure out what causes this thing to keep overheating...

 

what have u checked/replace so far

 

1.radiator is new...stock single core aluminum
2.water pump has been replaced 2X and its the right rotation
3.Thermo is good and been replaced 2x I put it in again today and made sure it was opening before i did
4.Both electric fans are on all the time and are in the right rotation
5 radiator hoses are good
6.Air dam is there
7.Coolant lines are all in the right place
8. No leaks around the intake
9. Deff not an airpocket..this has been going on for months
10.belts not slipping
11. 900 rpm idle in D..so i assume the water pump is turning fast enough
12. Put the stock crank pulley back on to spin the pump faster
13. Intake manifold gaskets are on the right way...no water passage blockage
14. No vac leaks (however the line to the heater control valve isnt getting vaccum?, but im sure that would be a small leak and couldnt cause it to overheat)
15. No lean codes, pulled 1 plug and it looked tan, if anything the car is running alittle rich)
16.No coolant leaks anywhere
17. Not using water to my knowledge

..i probably missed some stuff i checked, but anyway it overheats at idle for those who dont know..and if itll shoot up under full throttle too sometimes

 

u checked for leaks visually or with a pressure gauge?

 

visually i dont see any. I didnt use a tester.

Ive also done the radiator cap and im running more distilled water then coolant and water wetter on top of that.

 

just to make sure u have no leaks, do a pressure test.

 

How hot is it running? Are you getting that reading using the stock gauge? The stock gauges from what I know are not very accurate.

 

250 + on an aftermarket gauge

Seems to only begin to heat up at idle and depending on the temp outside will cool down when i move. Like today it was rainy cloudy and cold and it would go down to 175 while driving and had hit 200 after sitting for quite awhile

 

so around 220 the fans kick on and it still gets hotter?

 

fans are on all the time from start up (both of them)

I have them on thier own seperate relay that can make them come on at 180 or i can turn them both on with a switch

 

faulty coolant temp switch?

 

just replaced the temp sensor with an ac delco one.


Ive concluded that it has to be a flow probelm or my radiator is too small or something

 

I've seen a factory sized radiator cool ~450 hp or so.

Do you have sufficient air flow across the radiator? What gauge is it? How are you sealing the threads? Are there any visuals that it's actually overheating?

I agree, make sure you try a pressure test.

 

yea the radiator is getting proper air flow across it. Then fans are on all the time too so it shouldnt be a problem at idle either but it is. Im using a gauge from autozone rigged just to run for now so i can keep the temps in check. Its pretty accurate, the gauge was 190 and i had one of those thermal guns shot on it and it was reading 187 degrees.

Its a mechanical gauge too, and the threads arent be sealed in anyway, just screwing it into the block. Yea it has shown signs of overheating, rockers screaming in pain, coolant boiling into the resvoir etc etc

 

Ever completely flush out your cooling system (thoroughly)?

 

well ive done the radiator, and changed teh thermostat multiple times i figured ive blown almost any original coolant out of there, but if i wanted to drain it throughly, what do you suggest?

Ive drained it completely from the radiator, but never from the block i guess

 

yea complete flush would be good. maybe a blockage inside the block is causing insufficient flow.

 

I believe it's prestone that makes a pretty neat little back flushing T that plumbs into your cooling systems heater hose line or something like that. I you don't want to do that, I just yanked the blocks drain plugs and ran water through the water neck.

 

well im still battling the overheating issue. Today i realized my 2nd fan wasnt on..checked the fuse at the relay and it was busted. It then occured to me that running these 2 pretty large fans on one relay is a bad idea and that they might just not be getting enough power. Im gunna run another relay to the other fan tomorrow and see what happens.

 

did a complete flush today with that prestone gadget thing. I dont see any improvement...anybody else got any ideas?

 

Do the TPI's have a coolant sensor for the gauge and a seperate one for the ECM? If so, you might try replacing the one you haven't.

 

i ditched teh factory gauge sender and have an aftermarket gauge in its spot...and the coolant temp sensor is a brand new a/c delco

 

If you're not burning any antifreeze out of the exhaust and the pulleys/belt is good then the only other thing I could think to try is taking it to a shop to have it flushed, in case your prestone kit didn't do a good job. Besides that huge list you posted, a cracked head/gasket is the only thing I could think of but you'd see white smoke in your exhaust.

 

the motor is freshly rebuilt so i have trouble believing that my motor is clogged. My last bet is that my fans are going...but thats about the best ive got. I had the sniffer test done to make sure there were no gases in the coolant or whatever and it came up clean..so i believe the head gaskets are good and of coarse..no white smoke. Im gunna install ls1 fans and see what i come up with

 

Maybe check first to make sure the fans are getting enough voltage and that the alternator is putting out enought too (Fans not spinning fast enough). Otherwise I got nothing. Sorry mang.

 

thats what i was thinking... i had both of them rigged to 1 relay...so i was thinking it wasnt getting enough power. But now the fuse is blown to the 2nd fan so i figure the primary is getting all the power...but i havent seen any improvement. Even with the primary on and the heat on full blast...shell still overheat

 

Was it supposed to have two relays? If so, replace the fuse and get the relays back how they were supposed to be. Cheaper then buying an all new fan set up probably...Even with one fan going you shouldnt be hitting 250*

 

yea the factory set up of the fans stopped working..i tried everything to get the factory setup to work again. SO i bought a fan relay kit and wired em to that using a seperate harness and everything (leaving my factory one in tacked). The relay kit was designed to run two fans..but i dont think ones THAT big. Its a cheap advanced auto one...but its worked great so far. I figure i blew the fuse on teh 2nd fan bc it was drawing too much for the one relay to handle

 

i didn't notice if this was asked or not,... how far away from the radiator are the fans?

 

stock mounting i assume..i didnt change anything. Im still running the stock fans as of right now. Ill get back to you today though and measure it just to be sure

 

ok i got the other on a relay..no change. SO now ive got two fans on all the time..and then the heater on too and it still overheats. So its deff getting proper airflow...its got to be a plumbing problem.

 

im stumped as well. but going by this, would make me think at idle airflow is not sufficient meaning both fans are not turning fast enough. especially if the temp goes down once u move. just to be sure, the fans are blowing air TOWARDS the engine right? not away?

 

yup rotation and direction are good

what makes me think that its a plumbing problem is that if i beat on the car..itll start to heat up even while moving. If i cruise in OD at around 50 mph...itll be fine

ive never realize the "beat on/heat up" situation until today since the cold weather is gone..it's evident now since its hot out

 

how did the fluid look as u were doing the flush. any sings of gunk?

 

nah looked good to me

 

where are the master techs in this board?!?!?! lol

i wonder if its possible for coolant to flow too fast, and not stay in the radiator long enough to cool down. beating on it the RPMs will be higher than just cruising.

 

Without running tests or seeing results in person, it's just words around the block, nothing more. I still want to see results of a pressure test.

Coolant can and can't flow too fast. It can flow to fast if it's an open-cycle system (no thermostat to control flow). Then yes, the coolant will not stay in the radiator long enough for proper heat transfer to occur. If, though, the thermostat operates properly, then no, the faster the coolant moves, the better.

 

ok ok ill do the pressure test soon, i gotta get the gauge from autozone...im so tight on money that i just hate leaving 80$ there ...even if i do get it back hah

Ill get it done tomorrow or sunday and ill post the results

Thanks for sticking with me on this one guys, i appreciate it

 

Autozone's Loan-a-Tool program was created for a reason. See if they have a pressure tester you can loan out.

If you can, get one with the cap adapter as well. Inspect the cap seal and sealing surface while you are at it.

 

yea theyve got 1, i just gotta leave money with them first..im broke heh. But I just applied for a job there...maybe ill get it and then borrow it

 

I ran into a similar problem with my '95 Jimmy(4.3CFI/4L60E/4WD/4DR).I had flushed the cooling system,replaced the belt and hoses - this later to be my problem.Then for a couple weeks after she would run to warm on the highway.Well it turned out to be the lower hose. When I replaced the lower radiator hose I didn't transfer the spring that keeps the hose from drawning down/collapsing.Not paying attention to the details can come back to bite you.
And on the replacement airdam for the 3rd Gens.What a difference in size between the original one on my '83 Z28 to the good used one I got off a '86 Z28.This will definitly pull in more air at speed.But I think i'm going to get a spare to have on hand just in case.

 

hmm i noticed today...very hard to to see...but my passanger intake gasket may look like it has a small leak...ill grab a picture and show you guys..tell me what you think