ZF Trans. Running hot

[northshoreone]

My BW 250 ZF on the Port motor is running hot...20 plus hotter than the other one at 135 degrees vs 120 on the other side. When I slow to idle after running it creeps to 150! I have flushed it out forwards and backwards, checked for any water flow blockage and have found nothing. The center mark in nutrral is off on that trams. Is off just a 16th plus inch towards reverse. I have a hard time believing that would cause clutch slippage and heat. Oil level is on the mark and only a year old. Thoughts anyone?

 

[racclarkson@gmail.com]

It sounds likely your cooler needs more than flushing with water. Sounds like scale buildup. Temp rising some at throttle down is normal because raw water flow immediately drops. Fast idle will cool everything off faster than idle. Scaled engine heat exchangers will do this as well. But I would bet you're going to need to de-scale. Have you done the motor heat exchangers?

 

[Cricket]

Shoot the gear casing on both with an infrared heat gun in various spots to see if they're the same, write it down to be sure.
Swap heat sensors from one gear to the other, see what they read.
Hook up a manual temp gauge and see how that reads.

Those temps don't seem very high at all to me for a gear, but I'm a TD guy.
Btw, the oil should be changed at 1 year no matter the hours.

 

[racclarkson@gmail.com]

The temps are not hot. Swapping is a good idea, but the spike at slowdown tells me gauge is good.

 

[SEVEN]

I agree on the scale build up.

 

[Pascal]

I d start looking at raw water flow incl restrictions or impeller. Or an air leak on the intake side.

It may sound counter intuitive if the engine is not showing any sign of running hot but every time I ve had any of the above, th first sign was the gear running warmer.

 

[northshoreone]

Engine heat exchangers removed and cleaned a year ago and both engines running within a few degrees of each other. I have verified the temp. With a heat gun. The ZF tech that checked both trans a year plus ago said that the should not be run higher than 140 degree's which I thought was pretty low. The supply hose to the trans cooler is new silicone the return is not but looked fairly new so I didn't replace it at the time. I didn't remove the far end of the return line to check for blockage, thought of that last night...so will do that. When I replaced the supply side hose I did find some large zinc pieces in the elbow on the supply side of that trans removed them and flushed trans in both directions. If descaling is needed what should I use? ZF tech when asked a year ago said acid wash like flushing the AC units was not a good idea per him......

 

[Pascal]

How old is the impeller? Checked for impeller pieces at heat exchanger intake?

In addition to my comment on gear temp being the first telltale sign of a raw water flow issue, the symptoms were worst at low speed. In my case when spending a lot of time running at idle speed the temp of the tranny with less water flow would creep from 125/130 up to 160/165 over maybe 45 minutes. These are on the bigger ZF (forgot the model) mated to 1400hp 3412Es. As soon as we d start running at 1000rpm temps woudl quickly come back down.

 

[jim rosenthal]

I just had the gear coolers for my ZFs cleaned. I took them to T&S Marine in Crisfield, MD. They did the aftercoolers manually, but the gear coolers they just dropped in a bucket of acid and then pressure washed them. They waited until they were dry and painted them and gave them back to me.

 

[racclarkson@gmail.com]

Revives the discussion re removing HE for cleaning or cleaning in place. I tend to not disturb stuff that's working to keep from disturbing other stuff. Therefore, when I clean the HE in place I also get intercooler, transcooler and everything in the loop. That's why I asked if you did the HE's in my initial response. Something as mild as barnacle buster set up in a loop through the gear ought to have you shined up in a couple of hours. Send me a PM if you need the setup. Robert

 

[bobk]

Revives the discussion re removing HE for cleaning or cleaning in place. I tend to not disturb stuff that's working to keep from disturbing other stuff. Therefore, when I clean the HE in place I also get intercooler, transcooler and everything in the loop. That's why I asked if you did the HE's in my initial response. Something as mild as barnacle buster set up in a loop through the gear ought to have you shined up in a couple of hours. Send me a PM if you need the setup. Robert

Barnacle Buster is 40-80% phosphoric acid. Not really mild, but is fine for the HE cleaning.

Bobk

 

[northshoreone]

I checked the entire return hose and found no issues. The impellers are not quit two years old so I replaced them today. The bad part is I have to leave tomorrow and won't have time to see if the new impellers helped the issue until I return in July. If that's not the cure flushing with an acid solution will be next! When I had the heat exchangers cleaned the were removed and taken to a radiator shop for cleaning an testing. The trans. System didn't take part in that. I am a bit concerned that barnical buster may be a bit too strong for that job. Thoughts......

 

[racclarkson@gmail.com]

And then 4:1 water to acid.

 

[northshoreone]

Thats about what I use to flush the AC system about a gal. Of pool acid in a five gal bucket and circulate it with a small bilge pump set up. I have the system plumbed to either flush with the dock hose or flush with the acid wash. I have shut offs to each compressor so I can do one at a time. Works great to keep the AC going here in FL!I have some extra 1 1/4 hose and an adaptor to fit them to my bilge pump flush set up so it wouldn't be hard to do.

 

[racclarkson@gmail.com]

I became inspired. My gear temp gauges have never worked. It never bothered me. They don't get hot and I know the high temp alarm works. (Here is the part where you resist giving me your opinion on this practice.) Well I ran new wire and hooked up the gauges. One the thing is the gauges top range is way too high, 320. Did a two hour cruise today and got 105 indicated. Shot them with infrared thermometer. Holy carp, 170! Didn't make sense, I could hold my hand on them, no problem. Then shot raw water pump, 123! Well the water temp here is 77 degrees, and the impeller plate was very cool to the touch. Changed battery, no change. This piece of crap (Southwire) came from lowes. Who makes a RELIABLE infared unit?

 

[northshoreone]

I talked with ZF and they said that it is common for the Port Trans. to run hotter than Starboard. They said it is common for them to run between 15 and 25 degree's hotter. They also said that until it runs hotter than 175 degree's not to worry about it! Its well within its normal temp. range. With that being said it seems that my concerns about the heat changes are not really a concern at all. I will still report back after I have a chance to run it again and see what if any changes in temp. there are after changing the engine impellers. I asked about a slight oil leak at one of the sensors and they said to pull it and go to ace hardware to find a O ring to fit it! It seems that they ship the Transmissions to Hatteras with only a plug in the sensor hole and each boat manufacture installs their own sensors! FYI.....

 

[racclarkson@gmail.com]

Did they happen to say why the port runs hotter, or is it just that there are two of them?

 

[northshoreone]

They didn't really say other than something about one running in reverse and the other running in forward. Not sure why that would make a difference in heat generated in one vs the other though. Like I said, I will report back after I run it with new impellers in the engines. There had to be a reason for the creep in temp. on the port trans. vs no creep in the starboard trans. Stay tuned.....

 

[Top Hatt Craig]

They didn't really say other than something about one running in reverse and the other running in forward. Not sure why that would make a difference in heat generated in one vs the other though. Like I said, I will report back after I run it with new impellers in the engines. There had to be a reason for the creep in temp. on the port trans. vs no creep in the starboard trans. Stay tuned.....

New to twins, when I read that our Twin Disc run one in forward and the other in reverse to provide counter rotation, it bugged the heck out of me knowing one is shearing its fluid way more than the other, and the engine running the trans in reverse is working harder than the other engine.

 

[krush]

New to twins, when I read that our Twin Disc run one in forward and the other in reverse to provide counter rotation, it bugged the heck out of me knowing one is shearing its fluid way more than the other, and the engine running the trans in reverse is working harder than the other engine.

You know more about transmission design and their capabilities than Twin Disc, who's been in the business for quite some time? These transmission are designed to operate this way. In the old days, it was the engines that ran opposite direction.