Transmission overheating
Thread Starter
3rd Gear
Joined: Oct 2022
Posts: 3
Likes: 0
Transmission overheating
Hello, I have a c5 base with a automatic transmission that has 126,000 mile. Ok so I got a btr stage 2 cam, value springs, new water pump, dewitts radiator, new timing chain, headers, catted x-pipe and cat back. While I had that work done I told the shop to replace transmission filter. Well my problem is when the car is in park it can sit and run for about 45 minutes and not get over 215 for coolant temp, or transmission temp. If I start the car from a cold start, and put it in gear and hold the brakes, like I would be in traffic, both the coolant temp and the transmission temp get up to the 260's and give over temp alarms on the dic in about 15 minutes. If I'm driving the Temps are fine, and I've checked for trash on the condenser and in-between the radiator. Level of trans fluid looks to be ok. What should I be looking for, could it be in the tune, I was told in did absolutely need stall converter because it doesn't push through the brakes. Please give me some ideas. Thanks
Drifting
Joined: Sep 2009
Posts: 1,862
Likes: 594
From: Prescott, Arizona
With both coolant and transmission fluid temperatures going up that points to a fan activation problem. The fans should preclude temperatures much over 230- if there is no air still trapped in the heads from the water pump change. Air trapped in the heads would ordinarily present high coolant temperatures when driving, especially over 35.
First, get the fan activation verified.
Here is the description of how the fan system works:
Cooling Fan Control
The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. The ground path is provided at G102.
During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.
The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).
As an example, my car is an A4 with a DeWitts with both engine oil and transmission coolers, B&M finned aluminum transmission pan with extra capacity and an auxiliary transmission cooler in front of the condenser. I come off track when, around 10 laps at 100 degrees F outside air temperature the transmission temperature hits 250.
First, get the fan activation verified.
Here is the description of how the fan system works:
Cooling Fan Control
The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. The ground path is provided at G102.
During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.
The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).
As an example, my car is an A4 with a DeWitts with both engine oil and transmission coolers, B&M finned aluminum transmission pan with extra capacity and an auxiliary transmission cooler in front of the condenser. I come off track when, around 10 laps at 100 degrees F outside air temperature the transmission temperature hits 250.
Thread Starter
3rd Gear
Joined: Oct 2022
Posts: 3
Likes: 0
It's got something to do with the transmission it only does it when in gear and at a stop, like in traffic. It not air it the heads or the rest of cooling system. If it was air in the system it would do it in the 40 to 45 minutes I can leave it running in park and it never get much higher than 210
Instructor
Joined: Oct 2018
Posts: 206
Likes: 47
From: southwest coast florida
I would redo the entire transmission refill, new filter, new synthetic fluid procedure...making sure to do the exact correct steps as shown in the manual. Making triple sure you have the correct fluid level in the tranny.
