Bad day for an M52A1

[Gastrap]

I went to the local fire department to check out an engine noise complaint on their M52A1 brush truck, it has a Deuce bed on it with a water tank. The truck wouldn't even turn over when I got there, it could be barred over about 90° either way, but then stopped solid. I was hoping for a simple head gasket causing a hydro-lock, but found the old ENDT had dropped a valve. This is a DNR program truck, so it may just get turned in for something else instead of an overhaul or swap. Anyone just happen to have a good ENDT laying around? This one was a 70's depot rebuild.

 

[GopherHill]

Sorry to hear that. Even if you get a good replacement truck, there is still all the labor and expense of fitting out for fire service.

 

[Valley Rock]

Doesn't seem like it'd be all that hard to pull it around back and yank the head off, if the piston is "okay" and the problem is isolated to the head, then rebuild the head and pop it back on and run it for another 20 years .

Diesel pistons are pretty tough and can take some well above average abuse .

 

[GopherHill]

That is a good idea if labor and time is available.

 

[87cr250r]

I would plan on pulling the pan. The piston and liner will certainly require replacement. In the past I have bought piston, liner, connecting rods loaded together in a pack that you just drop in. If you only have to do one cylinder the cost isn't so bad. If reman is available that's even better.

But, this engine dropped a valve which is usually the result of recession. This isn't normally isolated to one cylinder. I don't know if there is a protrusion spec for this engine. If you can measure protrusion that is great. If not, you're going to want to pull the other heads and inspect the other valves.

 

[Valley Rock]

You can theorize all you want, but you have no idea what that piston actually looks until you pull the head and look at it, or see it with a borescope (if that's possible)

If the valve dropped it's due to a faulty keeper or broken/weak springs which can all be repaired on the non offending head w/o removal of the head itself, so removal of the offending head is all that is necessary and you will have your piston question answered muy pronto .

If they don't want to spend any money on it then buy it for scrap price and fix er on up !

 

[Gastrap]

Doesn't seem like it'd be all that hard to pull it around back and yank the head off, if the piston is "okay" and the problem is isolated to the head, then rebuild the head and pop it back on and run it for another 20 years .

No, it wouldn't be that hard at all, but I can see the piston is trashed. I'm a Deere diesel mechanic by day and I know how these end up... I'll just keep getting in deeper and deeper and then have to put it all back together when they don't want to do it right so they can turn it back in to the DNR. I just volunteered to diagnose it and give a couple estimates in case they bring it in to the shop for overhaul or swap.

Diesel pistons are pretty tough and can take some well above average abuse .

Here's one from another job damaged just from over-fueling it all day on a strip till bar, it doesn't take long to score a cylinder when things go wrong. I've also seen shrapnel from one valve or piston failure travel through the intake and waste another cylinder.

 

[87cr250r]

There is a word for that when parts from one cylinder trash another. It's called communication.

It would be unusual for an engine with any significant runtime to drop valve due to a faulty keeper or valve spring. Those are both infant mortalities. Recession leads to valve drops on higher hour engines.

I'm just saying, check the other valves.

 

[Valley Rock]

Broken/weak valve springs occur considerably more with age as the metal becomes fatigued, we know that, one would presume that since he did not show a pic of broken springs or beat up keepers or mention any of the above that they were "okay" .

Until it's pulled apart there is nothing but speculation .

Man, even if somebody had an engine for that thing they'd have to be close by or the freight would negate the cost !

 

[porkysplace]

You can theorize all you want, but you have no idea what that piston actually looks until you pull the head and look at it, or see it with a borescope (if that's possible)

If the valve dropped it's due to a faulty keeper or broken/weak springs which can all be repaired on the non offending head w/o removal of the head itself, so removal of the offending head is all that is necessary and you will have your piston question answered muy pronto .

If they don't want to spend any money on it then buy it for scrap price and fix er on up !

As he said it gets turned back into the DNR and then most likely sold on GSA, it's not the fire departments to sell .

 

[87cr250r]

"Broken/weak valve springs occur considerably more with age as the metal becomes fatigued"

I would argue against this because springs are an item that get reused during a cylinder head reconditioning. If that is the case, fatigue is not a factor in their life expectancy.

If a spring did fail due to fatigue then the others are close behind and all must be replaced.

 

[Valley Rock]

Cheaper than a new truck?

Free shipping, fleabay, sellet can convert to 24v no charge .


And for the record, a lot of these rigs never make it back to "turn in" they are often cheap sold right from the station, especially with a dead engine, don't ask me how I know .

 

[msgjd]

q

 

[msgjd]

fully dropped like that, there may be more damage than a ruined piston .. But of course taking the head off is the only way to know .. I have gotten lucky when I ran across a stuck exh valve here and there that only got bent a hair by piston, leaving a very slight mark on piston .. I would say worse case scenario is replacing piston, sleeve, valve and valve guide/head .. These parts for the 673 are not hard to obtain nor replace .. If you put another engine in there, I bet there are plenty on here that would take and repair that engine themselves, myself included .. Would love that mack in one of my M51's and have no qualms about what happened to it at the FD

 

[Gastrap]

No more work on this one, they decided to look for a different truck and are searching all the available ones in the program. They had an M1083 for awhile with a smaller tank and turned it back in, that leaves an M818 with a Deuce bed and an M1008 for brush trucks now. The A1 also has 8 bald 40 year old tires on the back, and a bad radiator, pretty rough after all these years of timber work.

 

[msgjd]

they should have no problem selling that truck , ESPECIALLY advertising it as a ENDT673 Mack and not a multifuel .. too bad it's too many states away from me and all outa time for projects, let alone have time to organize one heck of an auction before my boys do

 

[Mullaney]

they should have no problem selling that truck , ESPECIALLY advertising it as a ENDT673 Mack and not a multifuel .. too bad it's too many states away from me and all outa time for projects, let alone have time to organize one heck of an auction before my boys do

.
Yep. I understand the auction. Kinda sad, but I imagine the same thing will happen at my place. I figure there won't be any rush to sell because the house and shop are paid for. Hopefully that will give my poor green toys time to find good homes when I auger in.

 

[Gastrap]

A little update on this thread..

While looking for a replacement truck, the VFD found out a neighboring town had one in storage that hadn't run for 3 years. Upon inspection they found it was an M54A1! They got the OK from the town and the DNR and secured the truck. I found the IP had a stuck rack and 5 plungers, so I swapped the IP from the bad engine and it runs great! Pretty lucky to find another Mack powered truck so close.

The truck with the bad engine will probably wind up on an auction soon, either on-site or at the DNR yard near Ames.

 

[G744]

The Mack-powered G744 production run gave the military the best 5-tons ever.

Not to mention double the MPG over the gassers. Never the niggling things with the Multis.

Some will disagree, and for most of them, their entire 5-ton experience began with the 900's.

In stock configuration, the A1's will outrun and outwork the 800's.

I've driven both many miles, even to put more miles on my '67 than Uncle Sam.

Over 50k (lots for any tactical truck) on her now, and she still churns along just like it should.

 

[msgjd]

The Mack-powered G744 production run gave the military the best 5-tons ever.
Not to mention double the MPG over the gassers. Never the niggling things with the Multis.
Some will disagree, and for most of them, their entire 5-ton experience began with the 900's.
In stock configuration, the A1's will outrun and outwork the 800's.

I will agree 100% the A1's were the best 5T made when it came to hauling loads in the hills, no dispute on that.. With A1's I have passed gassers and A2's on hills having a slow lane.. Most of that was also due to the widely-untaught method of using 5L and 4L, instead of dropping into the slower hole of 3H as most drivers did .. However, I have always been partial to the R6602 gassers in mostly-level territory... They would outrun the A1's and A2's once the gear oil got warmed up.. And of course, the gassers we still had in the BN would always fire up in winter .. We avoided the 800's in winter, and the macks and multifuels may or may not start, depended if there was battery enough and other factors