Starting new project need help

[Hartgreen]

Ok so I just bought a 1967 m715 and now I need to get it running. It’s been sitting in a driveway for a couple years and it probably hasn’t run in at least 10. The brakes go to the floor with no resistance and I’m unsure if the engine is seized. Was thinking of starting by spraying lubricant in the cylinders and letting it set for a few days to get engine ready to start. Any tips here? Any thoughts on the brakes?

[Don Cavey]

The brakes on these trucks are very straight forward, nothing fancy. They use a single master cylinder that actuates all four wheel cylinders at the same time. There are conversions to dual if you do a search. But I elected to keep everything "stock".

Each of the wheel cylinders will need to be rebuilt no doubt or replaced. There are replacements out there and hopefully, your shoes did not get soaked with brake fluid and can be still used. The parts source for stock parts is somewhat dried up now. However, you can get NOS master cylinders from a few vendors and eBay. If the wheel cylinders are not pitted, the rubber is 1-1/16". You can get those from even the NAPA store.

As for the engine, you can start by spraying Kroil or WD-40 and let it sit for a while. You can use the huge harmonic damper attach bolt with the appropriate socket and see if you can bump the engine after it has had the penetrating oil sitting in there for several days. If it has had the carburetor on it, that is a plus since it tends to slow the entry of moisture.

Also, no doubt, the carburetor will need to be rebuilt. They are a very straight forward Holley model 1920. I have had good luck with the military rebuild kits. The rubber parts still seemed to be in good shape.

Good luck and pictures are appreciated!

[jhartings]

Here is a good site for brake parts, etc. I bought my pads and other brake parts from here a few years back.

https://www.boyceequipment.com/m37--m715-parts

[kyken]

Has anyone here used "Marvel Mystery Oil" to help loosen up an engine?

[warwick]

Welcome to the Zone and to M715s they are great trucks.

Are you going to restore the M715 to original? just want to get it running and driving?

Post some pictures of your M715 inside and out.

Up top above the site banner there is a link to the military manuals(TMs) for our trucks download them. The TMs help a lot in trouble shooting and repairing problems.

Search the Zone forums I'll bet 99% of you problems another zoner has had them and there is a thread with suggestion on fixes.

[Von]

Has anyone here used "Marvel Mystery Oil" to help loosen up an engine?

^ Good stuff right there.

I'd go ahead and plan on replacing the whole brake system. With luck your shoes and drums are still good, maybe the steel lines too, but most likely everything else will need replaced or rebuilt.
And a dual reservoir master cylinder swap is a little easier if you replace the steel lines at the same time.

[kwai]

The brakes go to the floor with no resistance

Well the jeep ads do state that the truck is unstoppable...

[Don Cavey]

Going back a few years... When I got my truck, I was told that it ran. There was no carburetor on the intake manifold, not that good because of moisture. The carburetor that I got was from a Chrysler Product engine, not the Jeep. I didn't know that at first. Anyway, my engine was stiff but not frozen. It tried to start but backfired and ran awful. The plug wires were reversed on cylinder 3-4. After I resolved that, it started and ran OK. It did smoke a lot at first. I guess I was in the process of honing the cylinder walls again. After running for a few hours, it stopped smoking and you could easily turn the engine over with the crank bolt on the harmonic balancer.

So, if you get it to free up, you can be good to go and don't be too discouraged if it smokes a lot at first. Hopefully, the reason it was parked was not because of a major catastrophe inside of the block. Check the oil, make sure it is not milky.

And when you get it running, if it has been sitting with no cover over the cab, expect the transmission to have water in it. Water will run right down the shifter and into the transmission. My truck had that issue. It shifted OK but rather sluggish. After taking the oil out (Looked like coffee, extra creme) and replacing it with good oil, gosh, what a difference.

Don't give up! Please let us know, please ask questions.

[Hartgreen]

Wow I hope youre right about the transmission. Or maybe not. I dont know how good it is to have water in it but it sounds like a fluid change will fix me up. I am having some issues with finding the location of the drain and fill locations on the transmission. Any help with that would be great.

[jeepdan]

Welcome
Don's post is spot on with good advice.
Remove all of the spark plugs and free it up by hand. Or at least make sure that it is free by rotating it by hand.
I have read that squirting automatic transmission fluid into the spark plug holes works well to free up an engine that has sat too long.
Once freed up, drain the oil and fill with new oil before starting in up.

Like Don said, don't hesitate to ask more questions. and we love pictures.