Quote:
Originally Posted by AHall
Since I follow this forum I check my coolant periodically and noticed the cap was extremely difficult to remove. It does not appear the threads were deformed as after I finally removed it I have been able to remove and replace. Fortunately I have no signs of a leak.
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I commented on the difficult to remove reservoir cap a couple of years ago when I first checked the coolant level. I needed both hands on the cap to turn it, and it was resisting until almost all the way off. I used silicone spray on the threads after wiping them down with a damp rag and the cap has been easily turned since. No difficulty with the other reservoir cap.
As with yours there was no deformity of the threads, so no cross threading had been done. I believe the coolant mixture acts as a bonding agent on the threads and causes the turning difficulty. Perhaps the hot environment pushes a vapor up into the threads, coating them? The rubber o rings also add resistance, but it can’t be much. No leaks in my system that I can see, but I’ve had to top up with 4 to 6 ounces of fluid a couple of times over the last 3 years.