Resolved: Two Boss Hoss ZZ4 Coolant Leaks

[The Mindless Philosopher]

I recently resolved two mystery coolant leaks on my 2001 ZZ4 Boss Hoss that I originally thought was a single problem. About 5 minutes after I'd shut off the trike after a normal run, I'd see a slight drip directly below the alternator. Approximately 10 minutes later, I'd go back into the garage and find a spray pattern beneath the alternator with a trail of coolant leading from it.

There were no signs of bleed-through from the back-side of the radiator fins and no expected hissing or gurgling usually associated with pressurized leaks. After removing the radiator, I discovered coolant puddled on the left side (as I faced it) of the timing chain cover. There were no discernable coolant trails leading to the puddle, but there was a noticeable trail on the block-facing side of the alternator shell. Figuring it to be a problem with the coolant crossover pipe along the front of the block, I removed it and chased down some replacement seals. It took a while, as local auto parts stores do not carry the larger seals, not even in variety packs. All they had were the smaller ones. I finally ran across what I needed on Amazon.

Here are the specifications for the coolant pipe crossover seals:
- Silicone O-ring, 70A rating, Durometer, red, 1-1/16" ID (27mm), 1-1/4" OD (32mm), 3/32" (3mm) cross-section (x2 required)
- Silicone O-ring, 70A rating, durometer, red, 1/2" ID (13 mm), 11/16" OD (17 mm), 3/32" (3mm) cross-section (x1 required)

The seals were definitely shot. Replacing them stopped the spray effect, but it did not resolve the puddling issue on the timing chain cover or beneath the alternator. Remembering that coolant used to seep from the two upper engine mount studs on the "passenger side" of the intake manifold, I pulled them out and wrapped the threads in silicone tape. I was careful to not re-install the studs too deep, as I have been told that the forward-most stud could rub against a pushrod.

Problem solved. No more coolant leaks.