New engine same old problem. Suggestions?
 

Ok here is the scenario. I had my engine rebuilt for the second time in 4 mos because of a problem in the cooling system or so it seems. Completely the opposite of most overheating problems mine seems to overheat while driving 65 --> on the highway. It seems fine at idle. Well even with the new engine the same thing is happening. I have not retaken possesion of the car from my mechanic because I want this to be fixed before I recieve it. He is the only one that has driven it since the rebuild.

I am looking for suggestions of what could cause this. Since the rebuild there hasn't been any coolant overflow and the stock temp guage has never moved but from monitoring the PFC we are able to see that at idle the temp stays around 90 but when over 60 or 65 the temp rises quickly to 104. I was wondering if it could be the temp sensor that the PFC is reading from. The reason I ask this is because the computer is only 8 mos. old, the engine has been rebuilt, the upper hose was replaced, the thermostat has been replaced with a lower temp one and the water pump has been removed and checked numerous times. Does anyone have any suggestions. Both my mechanic and myself are completely confused. Any help would be appreciated. Does anybody think it could be the PFC beacuse my mechanic says that he has used a thermometer(or something) and the temp doesn't seem to be going as high as it is reading. Also the PFC seems off when it is compared to my boost guage. I double checked the boost guage with a couple of others and they all read another 100 on the idle. I am about to install a temp guage but I was reserving the second pod of my A-piller for an EGT or AF guage. Let me know what you all think. Thanks in advance.

the 100 or so more you are referring to, is it the idle vacuum? If the people you are comparing it to don't have ported motors, then your will be lower, in the 370 range I'd imagine is about average depending on the size of the porting, while their's is around 450 roughly.

Tim Benton

Do you have A FMIC?? Your problems sound like an airflow problem. I do have a fmic (apex) and if my belly pan is not in place it runs quite a bit warmer on the highway, 89c with pan in place, and 95+ without. I also modded my belly pan so there is a dam between the pan, and the bottom of the rad so that no air can go under the rad. Hope this helps
J

It does sound like an airflow problem. On the highway you stay at a constant 3k+ rpms unlike city driving but the airflow should compensate for the higher rpms. If you do have the belly pan in place and don't have a fmic, I'm confused too.

Just to clear up the vacuum situation. The actual guage is reading higher than the PFC. I think I am pulling like 400 on the guage but just a little over 300 on the PFC. The 400 reading that I am getting was verified by a couple other guages as well. This is why I was wondering if all the readings on the PFC could be off a bit considering that it seems to be on the vacuum.

As for airflow, I don't have a FMIC and I know the belly pan was on correctly before the engine was rebuilt. I had to take it off to get a screw that I dropped when I changed the thermostat the first time. It was once again replaced when the engine was rebuilt and I am assuming since RX-7's are all that he works on that my mechanic got it on correctly. Thanks for the suggestions keep them coming.