Unknown small coolant pipe location. Help! Where does this belong?
 

My teenage son and I are putting back together a 1997 Mazda 626 v6 2.5L after changing the head gaskets. We're having trouble figuring out the location for this metal tube (small coolant pipe)--see attachment. . It has a rubber ring on one end, so I presume that end would connect to a metal hole somewhere. The 10 mm bolt would likely hold it steady (I'm not sure if the direction is correct on the bolt). The other end looks like it connects to a small coolant hose somewhere. I don't want to get too far into reassembly without knowing where this part goes.

Any ideas?

https://cimg2.ibsrv.net/gimg/www.maz...d5f78fc422.jpg

...or maybe it's not a coolant pipe at all. I'm really not sure where it belongs.

That looks to me like a vacuum or emissions line, but that is PURELY a guess. If I were in your shoes, I'd carefully proceed with reassembly and hope that the location became apparent. I imagine that there are lines and hoses hanging loose at the moment; do any of them match the diameter of the tube and could any of them give you a clue?

I wish I had a dollar for every part I've removed with the assumption, "I'll remember where that goes!" Some of them are still sitting on the shelf...

I found the attached image among the diagrams on the Jim Ellis Mazda Parts site (https://www.jimellismazdaparts.com/s...roduct=1887015)
The part labeled 15-520 looks like the part. However, there appear to be several variations for how it attaches. Maybe I'll be able to make sense of it by looking more closely at the engine we've got, but I thought I'd see if anyone else can make better sense of this diagram than I can.
https://cimg7.ibsrv.net/gimg/www.maz...141390def3.jpg

OK. I found where this part attaches to a hose attached to the oil filter. On this car, it is the hose that heads in an upward direction as shown in the upper left pop-up of the diagram that I included earlier. (I wish we would have remembered to attach this earlier before we reinstalled the exhaust manifold!)

y question now is where the non-hose end of this metal tube would likely go. It's pretty tight and difficult to see and feel in that area. Something (either the bolt or the end of the tube) must have attached to the head somewhere or I don't think we would have removed it when taking the heads off. Correct me if I'm wrong, but it seems to me that both the hoses leaving the oil filter would be taking filtered oil to the engine. One hose (the one leaving the oil filter horizontally) is routed to the engine block. Any guesses to where the hose leaving the oil filter vertically (and the tube I have) would be taking filtered oil? Perhaps another place on the engine block or somewhere on the head? I don't know enough about the lubrication system to know the typical routing, but perhaps someone with some experience can help me start looking in the right place. (Or if you have a KL V6 engine, perhaps you could take a quick look at where yours routes.)

OK. New theory. I think this is a coolant tube that is circulating coolant to cool the oil as it goes through the oil filter area.

I have a Toyota that has a throttle body with a coolant line running through it, I assume to keep the throttle body at a consistent temperature. Any chance this tube does something like that? Wish I could give you more informed ideas than that...

I discovered the location and installed it again, which was not easy after having put the timing belt, etc. back on. This tube takes a bit of coolant from the crossover pipe area between the two heads and circulates it around the oil filter to help cool the oil. The pipe runs behind the shield behind the timing belt. We must have removed it when changing the head gasket because it bolts to the front head above the oil filter.