AITG

I used to have about six U models with tip turbines. Occasionally the silicone gasket around the intercooler element would fail and make a vacuum cleaner-like noise. Pulling the intercooler and replacing the gasket usually fixed it. The corners of the gasket are thin - I was never able to get a used one to seal properly.

If I'm looking at the picture correctly it appears to have an air operated clutch?

At 70 I have arthritis in my lower back and a leg that doesn't have full motion thanks to a motorcycle accident. I got a GOOD Physical Therapist to teach me how to fix my shoulders and go to the gym several times a week to work out and lift weights. Thanks to all that, I can still change truck tires (R and R only - never have dismounted and mounted) and do my own maintenance on the motor home. That said, I still take way too long to get up off a creeper. OTOH, 25% of the people I went to High School with never made it this far. I won't complain.

The top light is actually a clearance light. The typical front turn signal on R models is a double-faced round assembly that is on top of the fender. I suspect that the reflective surface around the light isn't large enough to meet some spec in the FMVSS, therefore the additional reflector. Or, there were a bunch of leftover reflectors in inventory?

The little studs that held the light to the fender were subject to corroding as well as the light itself. A quick fix was a sealed Truck-Lite bulb that came with a protected plug and pigtail. A hole saw and you popped in the grommet which was also in the light assembly kit. That fixed it permanently.

I saw your comment on installing a radio and speakers: check to see if the truck is still positive ground. Mack held on to the positive ground system well into the 70s. The only real issue - besides not reversing the battery cables - was radios. Any of the aftermarket radios were negative ground and just reversing the red and black power wires resulted in making the chassis of the radio hot. Many bad things followed, as you can imagine. I do remember converting several trucks to negative ground but it's been too long to recall if the alternator had to be replaced.

Thanks for that information. Do you know if a specific fleet wanted this setup? I remember seeing a U model with a 903 Cummins once... I think some fleet on the East Coast wanted them for some unimaginable reason.

I saw this truck in an old data book but I always wondered if they ever actually built any of them. It seemed like a better choice than the Scania motor but they weren't exactly popular either.

Short answer: no. Long answer: the 300 and 315 engines had an air to air intercooler that was mounted to the intake manifold. The turbo drove a fan called a tip turbine that blew ambient air over the intercooler. This required a dual element air filter - one filter for engine air, another stacked on top for turbine air. IIRC, there is also an internal change in the pump that increased output pressure as well. So technically, if you had a 315 engine to scavenge a bunch of parts and access to the correct air cleaner and all the associated tubing, all you would need from there is time and money.

Awesome!! Thanks for your help.

In the late 70s / early 80s Mack sold an ESI service kit consisting of two oil filters, two fuel filters and a water filter. Does anyone remember the colors of the filters? I know that the fuel filters were different colors but I can't remember what they were. Thanks.