I have the 91 z28

It is very hot here in the summer, daily is in the 90s and the car will overheat when AC is on and i am sitting at light, etc..... if i turn the AC off, car will not overheat BUT I WILL! lol... Lately it has been in the mid 90s with heat index up to 105....

I also tested with the heater on and it will not cool down either. However it does look like the car will overheat faster when set to AC compared to Heat....

both fans are coming on and i have no idea what the problem is....

This is not a stock motor, it is a ZZ4 Crate motor rebuilt with forged parts and bored .030 over... It has a K&N ram air hood and intake...

Here is what has been done:

1) New Radiator hoses
2) New Water Pump
3) 160 thermostat with (1) 1/8 hole for slow movement
4) Primary fan changed to a Permacool 3000 cfm fan (doesnt seem any faster)
5) New Radiator
6) New Radiator Cap
7) New Distributor + Wires

Previously the Timing cover and intake front gasket was leaking but those have been fixed.... no leaks anywhere now...

Car does run cooler longer from start but it just cannot handle stop and go traffic in this horrible heat...

please help!!!!
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Also, Why are the coolant lines going under the engine block??

Does anyone have a coolant flow diagram for this car, i would love to see how the cooling system really works... I have a chiltons book but it doesnt show jack about this....

 

Unless I missed something, you don`t say that the fan switch was replaced. If not, remove your thermostat, drill 3 more 1/8 holes around the perimeter (4 holes seems to work best) and replace the fan switch with one that comes on at 185 or less and turns off at 170 or less. If you still have the stock fan switch, it does`nt come on until the engine gets up to about 225. Also, add 1 bottle of water wetter and use 30% anti freeze to 70% distilled water. When the car is stopped, shift to neutral. Do you have an oil cooler on your car? If the lines you are asking about connect to the passenger side radiator, those are the cooling lines for the trans, if there is an adapter plate above your oil filter, you may have part of an old oil cooler on your car. That`s all I can think of now. Good Luck.

 

ECU was reprogrammed a couple of times and during this the tech set the primary fan to come on at like 182...

yea i noticed the 2 coolant lines going to the oil adapter...

well i moved the aftermarket fan to the front of the condenser and put the stock primary fan back... we will see if this helps

also i did add water wetter and new coolant to the system since i had to remove the radiator again... argh...

still need to test this.... im also thinking the headers are making the coolant lines 2 hot???? the coolant lines by the heater core are right next to header....... this possible? Im thinking of taking the heater core lines out of the picture if still more issues... so i would run the oil adapter line up directly to the intake, bypassing the heater core stuff..... ?

 

Do you have a wrap around your headers? from what i hear that'll dramtically drop your under hood temp. also your new rad, is it stock style 2-3 core? i would suggest 4 core rad. Also when you say over heat are you going by the stock tach? or aftermarket or just know cus of the lovely boiling sound? p.s. if you get desprate just shove a big block of dry ice near the rad

 

No i dont have any wrap around the headers... i should have done that when i had my engine rebuilt.... the heat is shown because the lower steering shaft boot is melted and you can see the grease... lol.. not good... so i am looking into doing this soon but i hate taking the headers out of this car... such a pain in the a$$!!!!!!

the replacement radiator is a stock replacement so whatever stock is is what i have....

I am going by the stock thermo gauge... i would say its accurate when its hot cus if you pop the hood at 220+ you def feel the heat... ouch...

 

Stock being 2 core at best if i remember correctly, get a 3-4 core more cooling fins better flow ect... (I'll check for part number(s) for you monday night at work) i wonder if ne one make brass rad... gives off heat soooooo much better
and i hear you on that 220 deg heat!!! crap my stock 305 feels like a super nova when i pop that hood at times!!!

a pain in the @$$ it is with the headers but time well spent I would think

 

I THINK THE CONDENSOR IS IS GIVING OFF TO MUCH HEAT AND THE FAN IS SUCKING THAT HOT AIR THROUGH THE RADIATOR. I HAVE THE SAME PROBLEM. I THINK I WILL REPLACE MY CONDENSOR BECAUSE ITS NOT DISAPTING HEAT PROPERLY AND ADD A FAN ON IT TO HELP COOL IT IN HOT WEATHER.

 

Did alot of work on car this weekend:

1) put 3000CFM infront of condenser and set it as a PUSHER

2) Added Water Wetter to new coolant

3) since fan took up half of condenser on drivers side, i had to move off the tranny cooler and made a custom bracket that has it hanging between the bumper and condenser...

4) Replaced MAP senser plug because it was falling apart

5) Replaced vacuum hoses for cruise control, those were falling apart

6) Took out drivers side header (pain in a$$) and wrapped it good with header wrap

7) Installed new O2 sensor and reconnected my air/fuel gauge

8) Took out lower steering shaft as the header heat pretty much destroyed the upper boot and grease was exposed.. .etc... (gonna have to put a used one back in since this part is discontinued like most others)

9) Took out drivers seat as it needs replacing

10) Need to replace temp gauge connector as wire was exposed and it doesnt hold on anymore... I also noticed the black wrap for this wire got exposed to the header and was melting it...

 

How did the fan on the condesor work out?

 

havent tested yet.... still waiting to replace hower steering shaft and put in my new 4th gen seats (not shipped yet) ...

 

How did the extra fan work? Have you tested it. I put a shroud on that covers the whole rad. Core made from aluminum sheet metal $22. From home depo. Works better than with factory shroud about 10 to 15 degree temp drop with a/c on. Got the dimentions from summits fan shroud.

 

so you noticed a 10-15 temp drop since installing it?

I got the lower shaft installed, just waiting for the seats to arrive tomorrow to finish up... i guess i will look into the sheet metal

 

I bought a 36x24 sheet and 2 1x1x36 pieces of angle aluminum( L shape) cut one piece in half to make two 18" for the sides and cut the other one to 26" for the bottom. When you cut the sheet metal don't cut any off the height cause you will bend it over and screw it down behind the hood latch. As for the bottom it should fit snug in the gap where the factory shroud is, once you take it off you will see the gap. The only tool I used was a grinder with a cutting wheel. It easy took me 30 min. To make . You can do it. I'm wating on a 10" fan to come in to put on my condenser, 16" wouldn't fit unless I remove those 2 bar in front the condenser. Don't want to remove them but if 10" fan don't cut it I will.

 

Well today was the first day driving the car again, well last night was... no problems last night but today already, car starting creeping past the 220 mark.... this was with the 3rd fan on PUSHING air through the condenser.... once unplugged it went back to 220... next test is this afternoon in the 90+ heat... prob change the wires on the 3rd fan to push heat away from the condenser....

I think the prob is one or more of these :

1) the OEM fans with no shroud are just cycling the hot air
2) the coolant lines going to the oil adapter which run right NEXT to the header exit to Y-pipe get way 2 hot
3) the passenger header is making the coolant lines to and from the heater core 2 hot

** Passenger header has not been wrapped yet (pain in a$$)

ANYONE ELSE AGREE ON THESE?
**** Can i eliminate the coolant lines to the oil adapter??

What has been done since last post?

1) Drivers side header wrapped in header wrap
2) New O2 sensor
3) New MAP sensor Plug
4) New vacuum lines for cruise control
5) 3rd fan installed infront of condenser, currently set to PUSH through condenser
6) Water wetter added and more water than coolant added in system
7) OEM primary fan reinstalled
8) Transmission cooler moved off condenser to new bracket
9) 99 Camaro SS driver and passenger seats installed

Any help is appreciated

I am currently thinking on getting the LS1 fans with shroud next....

 

I purchased an LS1 setup from Hawks for $100 shipped.... should have by weekend.....

Afternoon test... started to go past 220 slowly during lunch so when i got home i disconnected 3rd fan in PUSH mode.... i decided to take a chance going back to work and set the fan to PULL mode to see the results... so far i am shocked... it got close to 220 but eventually went near 180-190 and stayed in the area....

im def not holding my breath yet but a small sign of relief so far...

 

I don't know what area your in. On the water wetter bottle I read the dyno test, it works best with 99 percent water and water wetter. If your in an area where it wont freeze over i would try it. A block heater during winter??? drain in every winter/summer and change the mix???just ideas that may help. lemme know what you think

 

also forgot to mention i replaced the temp sensor plug...

So i left off the 3rd fan today for a test to see if it really is making a difference... at around 1pm this definitely was a test as it is so hot out.... car slowly started to get to 220 and then slowly start to get warmer.... I got to the highway while it was alittle over 220 and got to work alittle past 220 and decided to plug back the 3rd fan in and it slowly started to cool down....

I originally thought that I had the fan in push mode but i think it was in pull mode at first, which didnt help.... I feel no air when its running now so looks like PUSH mode is helping the situation... atleast keeping it around 180-200 in hot conditions... more days to test/watch tho...

hopefully will have ls1 fans tomorrow to further keep the problem gone...
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if this is really the case... can a clogged or bad condensor really cause this car to overheat???

 

Have you tested your temp guage ? I put a mech. Guage in my car and my elec. guage has like delayed reaction. Still waiting on my extra fan to come to put on the condensor. After I put the shroud on it pretty much stop rising at 190 195. I would like to get it as close to 160 as posible which I need need to go with hypertec thermo master chip .

 

A clogged condensor wouldnt cause the car to over heat. A clogged radiator will. Check the basics, but also, hes a shot in the dark, this happened on the wifes cavalier. The tensioner was bad, so once the belt got soaked with water, it would slip. Put on a new tensioner and belt and it was all good.

 

5 days since last post... Car luckily so far only has been maxing out around 210 with AC on it this hot humid FL weather... This is with the 3rd fan on. Without the 3rd fan on it will continue to slowly overheat....

I hope to install the LS1 dual fans with shroud by next weekend to see if any improvement without 3rd fan running.... will update with more info then...

 

So what happen with ls1 fans.?

 

well i am still awaiting to get them from the place... they sent me LT1 fans and its been a pain to get them to ship me the right ones....

still hasnt got past 220 though with 3 fans

 

This thread was last updated some time ago but another member asked about a follow up...

I finally installed the 4th Gen fans (with shroud) couple weeks ago and the car has not gotten past 210/220 F when its 104 heat index in florida this year

I also still have the permacool fan infront so it does have 3 cooling fans

 

Thanks, Doing research on this site i came upon a post about anti-freeze and water mixing, according to a member if you have too much anti-freeze the car will run hotter than normal so thats something to think about.

https://www.thirdgen.org/forums/cool...-required.html