Jizzo17

I wasn’t necessarily looking to cheap out. I just didn’t know if there were any other options available.

Got a call back from the radiator shop today and the tubes were clogged to where it was only performing at around 25% cooling capacity. They flushed it out but the scale was so severe there were several holes that appeared. When one was fixed two more would pop up. I was quoted 2300 for a new radiator core but I was hoping someone on here might have another avenue for me to look into.

Okay thanks will do. do you advise taking the entire oil cooler off before I blow air into it?

I just took the forward facing end cap off. It’s the one that bolts to the water pump. The system will pressurize because it will blow the cap off the radiator if you remove it when it’s hot. i don’t have new gaskets but I can cut some out or get my Mack dealer to order some. I bought this truck from a lumber yard with 560k+ miles. I added the plus because the odometer stopped working at some point and there’s no telling when that happened. So I’ve become increasingly familiar with this truck the longer I’ve owned and operated it. But this is my first time with this type of oil cooler.

Here is a picture of the oil cooler tubes. I ran a wire through several of the holes and there is some sludge inside. Could I just blow air through them or can they be replaced?

Thanks. I thought so. Would it be possible for it to be plugged as well?

What is the round tube that the water pump forces water into? It’s in front of the 3 oil filters on the driver side of the engine.

I was afraid it might be the radiator. The old pump has a date stamped ‘86 on it but was not pitted and turned fairly easy when separated from the fan clutch. The fan clutch itself still had resistance. I have the radiator detached to the point where I was able to lean it forwards and pull the pump and fan out as one unit. So a few more hoses to unhook and I can lift the Rad out. Being as the pump was original I would bet the radiator is also original to this truck lol i am getting coolant flowing throughout the cooling system. Would plugged tubes still allow that?

How would I check for this? I may end up ordering a new water pump and slapping it on regardless. Would a new fan clutch be recommended as well?

I’m having a coolant issue on my 1985 Mack r with a em6-300. VIN is 1M1N179YXFA099577. I have flushed the coolant system at least 8 times with cascade powder. It was finally running out clear when I drained it so I put my new thermostat in, new water filter, and filled the radiator with the red coolant and distilled water at around a 55/45 ratio. It was holding temp at 180* with a few test runs I made but I was hauling gravel today and it got up to 230+. I wasn’t concerned at first thinking it might be a faulty gauge or sensor, but it started puking water out of the radiator cap. I parked it and let it idle but it still never came back down below 220. The fan feels like it’s pulling a good amount of air through the radiator. So I’m led to believe it may be the water pump. Has anyone else had any similar issues? thanks.

Okay thanks guys. Do I need to pull both seats out to get that floor pan off?

It is just a straight 5 speed. It won’t do it all the time. There is just a range of engine rpm and travel speed that it wants to pop out. Which is very close to the rev match to float into and out of gear.

I was hauling gravel yesterday in my 85 r model and under load 4th gear kept popping out when accelerating. I could apply just a few pounds of pressure to the gear shift lever towards me and it would stay in like normal but if I held it forward it would keep trying to kick out. Is there an adjustment that can be made to the linkage that will fix this or am I going to lose 4th soon?

I found a 90 that I need but it came out of a 75 Mack with a 5 speed. And the owner says it’s more like a .85 to one ratio. Does this sound like it could work for my truck?

@mechohaulic the ratio is 1:1. Tag may be there somewhere but just scraping the dirt off with a pick I couldn’t find it. There also wasn’t a washer in there when I pulled it apart. The only thing that came out were the two broken pieces in the picture.

The ID is 13/16. I’m not sure what ratio it is

Here is a picture of my the instrument cluster. The mileage also doesn’t move which is probably because the broke pieces I found inside the 90.

So the 90 is the problem. Where the rod is supposed to seat inside of a collar that has broken into two pieces and fell out when I took it apart.

1985 Mack R600st(?) VIN is 1M1N179YXFA099577 The tach and speedo in this truck is the style with the big clock in it. I am having issues with my speedometer not working at all and the tach bouncing rpms until it catches when I am in the throttle sometimes. I think there is a piece broken inside of the tube that feeds the cable running to the dash because I can turn one end and it won’t move the other any. Is there any way to have that piece rebuilt or can it be replaced? (I will attach a picture of the piece). I am also going to replace the cable. I am replacing the yoke seal coming out of the transmission so I decided to resolve this issue as well

@Geoff Weeks I’ll attach a picture of the wiring. You can see the 4wire and the 7. The blue wire the previous owner had run to a trailer brake controller that was under the steering wheel but it’s no longer there. So I just ran attached it to the left turn signal for the time being.

@Geoff Weeks, that junction box is where both the tail lights and the 7 pin plug for a trailer both meet. The 4 wire is ran from the rear up to the cab on the driver side then along the under side of the cab to the passenger side where it pops up through what looks like a factory hole in the cab corner floor. The 7 is ran from that box inside the cab to a hole somewhat behind the drivers seat. Where it exits between the glad hands. @cruiseliner64, thanks. Me and my brother think so too. We are planning to put a rear axle out of a wrecked truck in it so we can convert it to 10 lug and so the same for the front. But that later on down the road.

Link to the pictures since I couldn’t get them to upload

Found the junction box behind the passenger seat. Tucked in behind a black plastic cover. Thanks again for the help and here are some pictures. It was originally orange as well and the odometer shows 250k which I would think is about right for how clean it is.

Hello everyone. I recently purchased a Brig to use as a farm truck and am trying to get the tail lights and a 7 pin plug for a gooseneck wired in. Unlike my 85 Mack, this truck does not have a 14 point junction for the wires on the engine side of the firewall. It is set up with a glad hands and the 7 pin connector for a trailer and I could just tie in to that but I was hoping to do it a little bit cleaner than that lol. This truck does have the Cummins and 7 speed with a low ratio single screw rear end. Any help or wiring diagrams would be appreciated.

On my truck it’s the right turn that is the stop light. But the issue I’m running into now is that when I wire the red wire from tractor up, which is also the brake light, it flashes both my rear tail lights as if my hazards are on.