Torque settings for oil cooler

[asteven221]

The oil cooler on my IRM229 gearbox developed a leak, so took it to bits, cleaned everything up, installed new seals and a gasket and have nearly rebuilt it.

As I have had a bad experience over tightening brass bolts before, I am ultra cautious with this oil cooler. To be sure I bought a torque wrench at the weekend which has a range of 5Nm to 29Nm. Before using it on the oil cooler I decided to test it first and I am not sure if it's working! Maybe someone with experience could advise me - please?

I got an M6 bolt, locked it tight on vice and then set the torque wrench to 5Nm and put the socket on the bolt and applied pressure to the wrench expecting it to release quite quickly with the lowest setting. Needless to say it didn't release no matter how hard I applied force. In fact it eventually snapped the bolt! Thank goodness I didn't try it on the oil cooler.

It's has to be a faulty torque wrench? Yes? No? Should a setting of 5Nm be reached without a lot of pressure?

Also, I can't find a definitive torque setting for the bolts on the cooler but research for M6 8-8 suggests 7.5Nm. Do others reckon that's about right? The ZF manual doesn't give the settings nor does the Volvo manual.

Thanks a lot for any advice given.

 

[kashurst]

You are right to be cautious around brass bolts, they are easily snapped. I do it by feel with small screws/bolts, approximately fully home plus 1/4 a turn ish (hard to describe)
5nm is not a lot of torque. torque wenches I have used don't release - they "click" when you get to the required torque. If you keep pushing they will continue to tighten. Have another look at your torque wrench.

 

[cryan]

As stated above, torque wrenches tend to click and not give way. Some modern ones beep and older ones fold. Its hard to describe in words how much you should nip up threads in bronze/brass/alloy but a rough guide would be that if you hold the spanner between thumb and fore finger at the end holding the bolt you should not tighten it any more that whats possible by pushing the other end of the spanner with your pinkie. Obviously a rough guide. Some folk have stronger wrists that others
If using a torque wrench you could phone the manufacturer for settings. Guessing settings is completely pointless to be honest. Remember your generally only trying to nip the o-ring seal not flatten it so not much force is needed.

 

[asteven221]

Thanks for the advice. I didn't realise that the torque wrench would stay "locked" and keep tightening regardless of torque setting. I will test it again and listen carefully for a click.

Thanks again.

 

[elton]

Thanks for the advice. I didn't realise that the torque wrench would stay "locked" and keep tightening regardless of torque setting. I will test it again and listen carefully for a click.

Thanks again.

You should be able to feel it "click" through your hand.