Hi everyone, I have been working on a ZF trans in a hyster container handler. I went out to troubleshoot the trans for overheating. I found main pressure to be low 120psi and forward was at 100 psi, it's suppose to be 240 at idle and 260 at high. So I removed trans rebuilt it fully and dyno tested. All okay on our dyno. We also sent out the cooler to be flushed and checked. I reinstalled the trans and test drove the machine. It's not going into the red on the gauge in the cab but its pretty close. It also reading pretty high on the temp gun 93celsius. I also noticed the coolant temp is getting up there to. The engine temp with the heat gun is at 103 celsius when the trans is near the red. I also notice in the cab on the gauge the engine oil pressure is low at idle and picks up at high. I checked all the pressure on the trans and all are good. Also checked the flow in and out of the cooler it's good. I think it could be three thing thermostat not opening fully, water pump isn't circulating the coolant enough or the engine is creating a lot of heat. If anyone has any more suggestions or ideas on what else I should check that would be great.
What is the temperature drop across the trans cooler? Did you check the converter bypass valve when it was apart? What kind of condition was the converter in, any excess wear?
Is the trans cooler air cooled, or engine coolant cooled? If it's air cooled, the engine heat isn't much relevant, EXCEPT that they both point to low air flow-fan belt, gunked radiator, fan flipped backwards? In either case I would be looking at the temps going into and out of the radiator, both air and coolant, and the oil temps. If the radiator is too hot top and bottom, to me the airflow is inadequate, Nige would say the water passages are gunked up internally, your call. If the bottom is cooler than you'd expect (more than ten C cooler than top) I'd look at the water flow-tstat, plugged radiator passages, water pump.
The trans cooler is coolant cooled. When I put a heat gun to the radiator top section it reads 75C and At the bottoms 32C. Also found this black gunk inside the radiator. Going to put a new water pump in and send the rad out flushed. Thanks for the info.
Yikes! I hope that's not the same stuff Randy dealt with in his fuel tank in an epic thread here. "Bars leaks"? asphalt that would only soften with acetone. Cooking a transmission is a little more expensive than getting the radiator fixed right in the first place. What did the coolant side of the oil cooler look like? I pulled that 10degrees out of my ass, but I'd say 40+degrees means something is blocked.
A good rule of thumb for a coolant (engine) radiator operating correctly, in other words not blocked in any way, is maximum 10-12 degrees of difference between the temperature of the inlet and outlet hoses. Signficantly more than that as in this case and the radiator is plugged internally so low coolant flow through the rad but the fan is cooling what little gets through pretty well. Significantly less difference and it's likely plugged externally/fan issues so low heat transfer from the coolant to air flowing through the rad. Personally I wouldn't be just doing a rad clean and water pump change but also a complete cooling system flush with whatever was the most agressive cooling system cleaner I could find. What comes out might frighten the feck out of you .......