right now my car is getting up to an operating temp of over 220. I talked to Tuned Performance (who did the tune and changed the temp the fans kick on) and he says theyre supposed to kick on at 200 and 268 super hot. the passenger side fan wont come on unless i jump the relay (tried a couple different relay's and it didnt help). I know it has a lower temp thermostat, it also has all new sensors in the heads and i think i replaced one of the sensors in the front of the intake manifold. anyone have any ideas on why its not kicking on? Tuned Performance suggested maybe the gauge was wrong, but i can't remember which one that is to see about replacing it.

also, the heads i'm using have too large of a hole to accept the sensors themselves, so i had to use a brass adapter, do you guys think that could be the issue too?

any thoughts or help is appreciated.

 

you can have your temp gauge calibrated,or just replace it with a NOS one.i swapped out mine with one i got from franzen chevrolet.they commonly go wonky on our cars . you can also check your operating temps with one of those infrared temp guns.good luck

 

I'm not too sure it has gone wonky. I pulled the 305, put in a newly built 350 and then this started. I do have an infared thermometer, where do I want to point it at for the most accurate reading? Just the rad cap?

 

take readings from the top and bottom of your radiator,also the thermostadt housing, the intake manifold,and the heads.it would also be a good idea to take readings from your exhaust. if you have headers you can get an idea of the temp of each cylinders operation. if your readings from the engine are ,near 220 and you have the proper 195 thermo .you are ok

 

The factory 2ndary cooling switch should turn the fan on at 242?...IIRC, there is no control for that (2ndary fan) in the PROM as far as I know....maybe you misunderstood him?

I'd replaced my 2ndry switch with an on at 195/off at 180..as the 2ndry relay over rides the primary, both fans turn on at 195.. ECM never gets a chance to control the primary relay

 

do you know wehre to pick one of these up at? i'd normally go to my local napa store, but they usually just give me the stock part for the car.

i'm wondering if the lower temp thermostat has anything to do with it? or maybe the new heads are running hotter than its supposed to?

 

I got mine at some speed shop in the Bay Area years ago, but IIRC, it was a Hypertech.

I'd bet a quick online search would find the results.

The switch (looks like CTS) is under and between #6 and #8 plugs

 

PS...

As I recall, the ECM turned the primary fan on at 220-225 (or so) so no worries about running too hot...yes, it isn't nice to see the gauge that high, but that's how GM made them for emissions...mainly for idling.

Thing is, if your running 220+ down the highway, you have other problems as well.

 

Here's the one I got...my numbers were off a tad...age thing...at Summit:

http://www.summitracing.com/parts/HYP-4028/

 

hmm...ok, thanks for the info. i'll have to see if any places around here can get it. summit says its not available. wouldnt hurt to have the other fan on earlier anyway lol

 

Here's a list of other possible switches. I finally went with the one for the TurboBuick, (SW555) on 210 off 200

SW555
SW505
SW500
SW502

https://www.thirdgen.org/forums/cool...tched-pns.html

Make sure your thermostat is at least 10-15 degrees cooler than your turn on temp. AS an example, a 190 thermostat starts to open at 190, but won't be fully open until 200. If your cooling fans turn on before the thermostat gets open, not sure you would ever get up to temp properly.

 

thanks guys, i ordered the hypertech sensor. hopefully for $50 it fixes the problem lol. i may have to look into a new temp gauge sensor, cuz Tuned Performance told me the primary fan is supposed to come on at about 180 degrees, but yet it shows it not turning on until it reaches over 220 degrees. wouldnt be the first time a brand new sensor has proven to be bad....had an oil pressure sensor (near the intake manifold) tell me i had about 60psi in a 305 with 160k miles while at idle.....when i told the store they said "gee i wish my car had that good of oil pressure" lol

 

have you verified the actual running temp of your engine?? is your coolant recovery tank boiling?? do you have any indication that you actually have a overheat condition?? a proper fan switch is a good idea,as mentioned however you should not rely on the gauge reading till you have verified your operating temp. NOS gauges are readily available should yours be inaccurate. I went thru a similar problem with my 86 IROC. investing in a IR heat gun answered more questions than I had thought to ask.its a handy tool

 

i havent gotten a chance to yet (i work 12's and my car isnt at home and i wont be back with it till monday) but i'm going to check it then. i did want to keep the motor running cooler so the secondary fan switch is a good thing. i havent seen my coolant tank boiling over, but my rad cap did have boiling coolant starting to force its way out before i jumped the relay to get the secondary fan on.

 

I think the secondary fan temp switch doesn't trip until around 220..... and that will turn on both fans......

Isn't the primary ECM controlled? OR is this a custom setup?

 

Did you check the radiator behind the A/C condenser coils??? Mine were completely filled with crap.

 

i believe the primary is ECM controlled because Tuned Performance said he set it up to turn on sooner with the PROM chip he wrote for me.

also, i did not check to see if its filled up with crap, but i had this rad in my car for the past 10 years of owning it. the car had a 305 for all of the past like 3 weeks when i swapped in my 350 i just got done building. the rad and the temp of the motor never gave me any issues like this. i put all new sensors for the coolant everywhere but i still have to double check to make sure that they're not faulty too. i am just not too sure how the motor would be running that much hotter, if it is in fact the motor.
i wasnt supposed to use a different radiator between 305 and 350, right?

 

I did a 350 swap in 2002 and did not change the radiator. I did change mine when I started having overheating problems, and I used a stock replacement one.

 

ok, i figured there wasnt a difference in rads between the motors. i do see that summit makes a bit larger rad, i may look into that in the future if i can't get the temps to even out to where they used to be. tomorrow i will be checking it with a thermometer though to be sure.

 

today i got over to my parents house where the car is. started it up and let it run for a while to use my laser thermometer thing on it. i found the gauge is in fact wrong like you suggested. the fan kicked on right at 180 degrees where Tuned Performance said it would, although the inside gauge said the car was well above 220 (maybe around 250).

so that raises a smaller question, i had gotten a new temp gauge sender when i built the motor from Napa. I went online, saw they list like 5 or 6 different temp gauge senders, all at different temps. anyone got a part number so i can order the correct one?

 

its probably NOT the gauge sending unit in the left head. more likely ,its a bad gauge .which you can replace with a NOS one. I got one for my 86 from franzen Chevrolet.but there are other sources as well. its not a bad idea to replace the sending unit too. but more often than not its the gauge that goes wrong. hawks third gen.can sell you a replacement gauge if you cant find one elswhere

 

The gauge was working perfectly fine before I switched out the senders. I would normally agree, but even how the sender attaches is different. Before it was sorta a "T" at the end and the plug slid over the end, the new a has a regular straight male piece that the parts guy said "should work" which makes me leery its wrong.

 

Shouldn't be a problem, the autozone pn is TU66 and it's a blade terminal. I've sold one to a gal with an 88 camaro and we never got the part back. My car still has the goofy T terminal. If you find an original with the T terminal please post. Should mine go out my headers and the bracket to my ac are rather close to the temp sensor. The spade connector may put the wire too close to the bracket and I'll have melting issues.