to start off I recently put a rebuilt stock motor in at the end of last year. last motor with hotcam in it ended up blowing so i started the rebuild. Now that it has been installed I have noticed that the temp gauge will go to the third dash mark on gauge cluster before fans kick on. the scan tool reads that temp hits 228 when #2 fan kicks on. it drops down to 205-210 ish before the #2 fan turns off.

Hasn't officially overheated and gushed out coolant but it concerns me because my last motor never went past the 190-210 mark as far as i can remember.

related items replaced during rebuild included: Radiator (old one restricted), T-stat (oem 185 degrees), rear cylinder head coolant crossover with banjo bolts (I believe that is correct term), and radiator cap (oem with safety vent release). also currently has no catalytic convertor.

used old water pump only had 1k-2k on it before last motor blew.

Tests performed include pressure testing cooling system ( no drop in pressure at 20psi over 20 mins) and a Block test with engine Idling/2k revs from cold start all the way to when thermostat opens with no change in block test fluid color. also no smoke out of the exhaust and no coolant/oil mix in radiator or under oil cap.

ideas where to go next would be greatly appreciated thank you

 

You're pretty close to normal on temps, and when the fans come on.

 

I don't see any problem with your current setup. If you want cooler temps install a 160-degree thermostat and a fan switch OR PCM reprogramming for earlier fan activation.

Was your old motor/combo stock I am assuming?

 

What are you calling the #2 fan? Both fans should be running. Maybe that has something to do with what you are experiencing, but the temps are really not an issue. Please verify car and year you are working on.

 

sorry for the late response, the vehicle is a 94 trans am lt1 6s. prior set up was with hotcam, 16rr, full bolt on etc. now everything is stock besides headers back and moroso cold air. I have a new issue however.

The hi temp I can live with for now ive gotten more comfortable driving it knowing that it will not boil over. But now I am trying to get it smogged before I can register it again (no-op for 3 years). my issue now is that im having a surging problem in all gears during acceleration. for example if I take off from a dead stop it feels like the motor is losing power then gaining power. I have checked vacuum leaks with carb clean around manifold and vacuum hoses, sprayed igniton wires for arcing/checked for burnt wires, and checked live data on my scanner for anything out of the ordinary. any ideas on my next step would be appreciated

 

You indicate you have "T-stat (oem 185 degrees)". Stock t'stat is 180*F. Do you have the correct "LT1" piece?

 

My mistake on first post about oem temp, I found the receipt and this is the thermostat i have currently installed.

MCS Murray Temperature Control 4218 - Standard Thermostat | O'Reilly Auto Parts

 

my ethos scanner was only reading that fan #2 was engaging, I found that relay for #1 fan was missing. replaced it with new relay now they both work.

 

LOL. That should help.

 

Appears to be the correct part:

http://shbox.com/1/tstat.jpg

 

well I still have issues with the car. I tried to smog it and it failed on nox. here are the overall results.

15mph Failed
CO2% 13.8
O2% 0.7
HC 21
CO% .01
NO 959 (max 689)

25mph Failed
CO2% 13.8
O2& .7
HC 22
co% .01
NO 985 (max 706)

I have checked BLMs and they are seem to be changing quite a bit. some days I will idle and it will be around 128 on right and left, other days it will be 160 on the right and 145 on the left and then slowly make its way back to 128.

I noticed that C02% is 13.8 which to my knowledge should be 14.7 to be stoichiometric. I have checked for vacuum leaks ie carb clean around vacuum lines and intake after MAF and have found nothing. also when the BLMs spike the car runs really rough. if i go WOT it bogs and clears up all the way to 5k rpms.

where to go from hear?

 

"Stoichiometric" refers to the A/F ratio.... that's what is 14.7:1 (14.7 pounds of air combine with 1 pound of hydrocarbons), not the CO2 content.

High NOx is a sign of running lean, and/or running too hot. The low CO and HC indicates it's not running rich. High NOx may also indicate your EGR system is not functioning.

You indicated the BLM's "seem to be changing a bit". Do you mean that within any given BLM Cell the numbers change rapidly, or are you just seeing the BLM's change as a result of the PCM moving between the cells as RPM and MAP change?

 

As far as the egr goes it does have a new valve and the vacuum line from the manifold to.the solenoid and the solenoid to the valve are connected and free of any cracks/leaks.

The blms i notice change while idling from the moment i turn it on it may be at 160 blm at idle and letting it warm up (only idling) it will drop back down around the 128 range on both banks.

 

update

I let the car idle today with the scan tool hooked up and after 5 mins or so all numbers seemed ok ie O2 sensors switching from hi-low, blm around 128-131, maf at 8-10 gpm.

But at about 15 mins my CEL came on with code 44, left bank too lean, so I switched back over to live data and found the left bank O2 hovering around anywhere from 4-140 max mv while the right side was between 53-912 switching normally. blm on left at 160 while right was at 128. I also held the throttle at 2k rpms which at that point the left O2 stayed around 4-12mv max, it never did get above 12 mv the whole time I had the motor at 2k rpm.

while it was doing this I sprayed carb clean around vacuum lines, intake manifold, and Left header to see if I would get any change but nothing. this is driving me crazy with my wedding this weekend and only 30 days for a free retest on smog I want to get this thing running right!

Any help would be really appreciated

 

Have you checked the timing? I know its hard since the stock balancer doesnt have marks on it but timing can make it lean, lean will make it hot. Could you have missed the mark putting the motor back together?