About 2 years ago I took my L67 out of my fiero and replaced head gaskets as well as all of the other necessary gaskets to replace the heads and supercharger. I purchased the head gaskets from zzperformance and made sure to get the left and right head gaskets and carefully lined them up when installing them. At this point I also bought a new thermostat cap from the help section at advance. When I put everything back together I noticed that my car would come up to temperature and the fan would turn on but the inlet at the radiator was cold. I can run the engine without the thermostat and the fan cycles like it should. The computer seems to be programmed to turn the fan on at 185* and turn it off at 175*. When I run the engine with the thermostat in I see the PCM reads the temperature goes up to 185*F and kicks on the fan at that temperature. The temperature keeps rising until it gets to 191-194 and then it levels off. The temp can reach 200-201* but that is the highest I've seen the temp in 100* summer weather.

I have replaced the thermostat with 180* stant thermostats a few times at advance thinking I am getting the wrong thermostat. I have also replaced the radiator and the water pump and am still experiencing this problem. Has anyone else had this problem with a 3800 swap? I'm using a modified fiero thermostat housing and have blocked off both of the 3800's normal heater core ports. This all worked just fine before I took the engine out and put it back in and I believe I had the computer re-programmed by Darth to accommodate the correct MAF sensor as well. Any help you can offer would be greatly appreciated!

Thank you!

[This message has been edited by JamesCurtis (edited 08-09-2013).]

I don't think a 180* thermostat is fully open until it it around 190*. If you want it to run cooler than that I would put in a 160* and see if it brings it into the range you like. There is a lot of water in the tubes to the front, so it may just take a little time to warm it all up. When the Tstat opens it gets cold water from the tube from the front, and there is a lot in there. Larry

What do you mean by blocked off the original heater ports? You do need the LIM heater outlet connected to heater core or atleast looped back for it to flow properly.

It's normal for it to get a little bit hotter than the tstat for the reasons the previous reply stated. I wouldn't go with a 160 tstat unless the car is just setup for racing, a better idea would be to get or make a drilled 180 tstat.

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86 Fiero GT 4spd - L67 swap: VS cam, GenV. Needs exhaust (ETA 9/13) Build Progress
98 GTP - Some mods

[This message has been edited by sco77 (edited 08-09-2013).]

^^^ Agreed, I saw similar coolant temps when I ran a 180 thermostat in my GTP.

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Project L67 Fiero

quote Originally posted by sco77: What do you mean by blocked off the original heater ports? You do need the LIM heater outlet connected to heater core or atleast looped back for it to flow properly. It's normal for it to get a little bit hotter than the tstat for the reasons the previous reply stated. I wouldn't go with a 160 tstat unless the car is just setup for racing, a better idea would be to get or make a drilled 180 tstat.

It's blocked off. I can reconnect this circuit but I've seen a number of people do this in PFF threads(I know that doesn't necessarily mean that makes it the right thing to do). If I am damaging the engine then I would like to know so that I can remove these caps and tap them to complete the circuit. Right now my heater core is fed by the modified fiero thermostat and uses the built-in return on the passenger side coolant line on my 88 gt. I would be suprised if Ryan at Sinister Performance would incorrectly program the fan on/off temps for as common of a modification as a 180* stat is. What are your fan on/off temps set at on your 3800's running 180* thermostats?

[This message has been edited by JamesCurtis (edited 08-09-2013).]

Perctly normal....

quote Originally posted by MstangsBware: Perctly normal....

Can you elaborate? I don't think that having my radiator fan run 100% as soon as the engine warms up and then never turning off until I turn off the car would be considered perfectly normal. Right now my engine sits at 190-200* when warmed up and my radiator fan is set to turn on at 185 and off at 175. Do I need to have Darth adjust the radiator fan settings? I have informed him I'm running a 180* thermostat and he didn't think that this was normal either. What are your fan on/off temps for your thermostat?

[This message has been edited by JamesCurtis (edited 08-10-2013).]

Guess you could get it to turn on at 205 or 210, but then your car will probably cycle between 190 and 210 as the fan goes on and off and the Tstat opens and closes. I think better to have the fan running before the Tstat is fully open. Larry

quote Originally posted by JamesCurtis: Can you elaborate? I don't think that having my radiator fan run 100% as soon as the engine warms up and then never turning off until I turn off the car would be considered perfectly normal. Right now my engine sits at 190-200* when warmed up and my radiator fan is set to turn on at 185 and off at 175. Do I need to have Darth adjust the radiator fan settings? I have informed him I'm running a 180* thermostat and he didn't think that this was normal either. What are your fan on/off temps for your thermostat?

What u described above is exactly what I have seen in all the 3800 swaps I have done. Even running a 185* stat as the stat really doesnt open to 190-194 in my experiance . Once the fan comes on as programmed the remps never make it back down to allow them to **** off.

I just wanted to update this post with the resolution. I ended up moving the fan output wire to the high output from the pcm which changed the fan on/off from 187/183 to 194/190. My fan now cycles as I would expect it to. The weird thing is that I have two stant superstat 180* thermostats and one would fluctuate between 194 and 196 while the other would fluctuate between 185 and 189. I used the thermostat that fluctuated between 185 and 189. Thank you all for your help!

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