Coolant Took A Vacation

[aleigh]

Working on the (other) LMTV

Well last night I took the LMTV out to the grocery store (ha!) and noticed in the parking lot that it was spraying a fluid on the inside pax side wheel well. I thought it was hydro or maybe a oil leak - oil level was good, coolant was good, so I drove it home. When I got home ten or fifteen minutes later, all the coolant had departed, or anyways the tank was empty. Temp gauge and all that was normal on the trip home, although I am not sure what the temp gauge is actually measuring (e.g. an empty coolant line vs. the block temp).

What is that they say, start worrying when it stops leaking?

It sprayed all over everywhere so I need to clean the engine off and run some water through it to try to see where it is leaking. At first glance it looks like maybe one of the fittings on the front pax side of the engine.

Have I ever mentioned how I really wish I had a remote start/kill switch like an A1? Climbing into the tipped cab is stupid even with a ladder. I also noticed when I opened up the tank there's a lot of scales in there, around the filler. It looks pretty nasty actually but the rest of the tank looks clean. Not sure if it just collects in the neck because there's a void or what. I've never had to open it before since I would just normally check the sight glasses.

 

[AZK9]

Sorry to hear you're having this problem. Mine is just a deuce, but because my radiator went bad...
I've actually learned a lot about the entire system. Once I had 'opened up' everything, I was pleased
to discover that everything inside was very clean.

I suppose it's possible that the previous owner used 'high mineral' water to mix with the antifreeze.
That might leave the scale you're seeing. Good luck with your repairs.

 

[Suprman]

Flush the system. The overflow tank is aluminum if its starting to corrode you dont want that circulating in the cooling system. If you flush and get water in there then you should be able to use a pressure tester to see where the leak is coming out. Or just pressurize the overflow tube with air.

 

[aleigh]

It's not that the tank is corroding I don't think, it's that material has been building up in the neck. It looks more like they used regular tap-water and the minerals crystallized. If I look inside the tank it looks bare and clean.

 

[mkcoen]

I'll keep my fingers crossed it's something simple. The amount of relief I felt yesterday after figuring out I just had a broken hose clamp on the turbo versus something majorly wrong is indescribable. Here's hoping you have the same luck

 

[aleigh]

It was something simple - I poured a couple of gallons of distilled water into it until the tank was full and fired it up. It was leaking pretty good out of one of the fittings, which turned out to be finger tight. Tightened it up and it holds water fine now. I've got pictures to post but now my problem is my cab won't come down. Hydro thing kind of pumps - you know pop pop pop like it does - every few seconds and it seems like it's building up a lot of pressure. Valves get hard to turn on the hydro board - then it feels like it releases the pressure and it'll pump up a few more times before it gives up.

Spare tire crane came down fine, won't go back up. Oh well. Off to the TMs I guess.

 

[aleigh]

Sounds just like http://www.steelsoldiers.com/showthread.php?148665-Cab-and-spare-hydraulics-problems-M1078-LMTV

 

[aleigh]

Sigh, "If you see puffs of "smoke" coming up then your internal pump seal is bad and will need to be rebuilt.".

Yep.

 

[aleigh]

Spamming my own thread...

Yeah so it's some kind of valve on the low (relief) side I am all but certain. If I pump the manual jack I see the lift cylinder move ever so slightly and then it springs back. And the manual jack is all springy too, it's just building a ton of pressure on that side. Probably explains the oil puffing out the seal too.

 

[Lmtv772]

...

 

[mkcoen]

Mrosupply.com has the seals.

 

[aleigh]

The part I don't get is why would the seal in the air pump be causing back-pressure on the low-pressure side? I can understand why it would be blowing out of the pump on the high pressure side if there was another unrelated problem on the low side and the pressure was too high - and I think that is happening, I am getting blow-by due to some other problem.

I have the same symptoms when I use the hand pump. A few pumps and then it comes up to tremendous pressure. Been going through the TMs but they do not seem to cover this case. I'd love to take it all apart - except, I am worried about loosening up a fitting at 2500 PSI. The TM wisely tells you to drain the pressure at the start of all the procedures first but doesn't actually say how! Or if it does I haven't found it yet, and I've been over both the troubleshooting tree for hydro and all the repairs.

PS before this happened, I had at least one leaky valve on the hydro panel. I had been avoiding fixing it because it's a pain in the ass to get the panel out and now I think I am getting what I deserve.

 

[Lmtv772]

...

 

[aleigh]

I tried that and for sure - no.

I know people make mistakes and it's good to point things out but I have the basics covered - there's plenty of fluid, and I've operated the valves lots of times, I know how they work.

Something is clogged on the low side. Just so we're all clear what I mean by the low side is I mean the circuit past the cylinder. So here's exactly what happens -

Pick a circuit, any circuit. Pick raise or lower. Initially the pressure is relatively low. The air pump will get in a few pumps, or, you can pump it with the manual pump some number of times. Then it becomes very very difficult to pump. I can see the cylinders trying to work with the power strike but then they bounce right back to the previous position. In terms of the cab falling, that requires the low side to relieve pressure, and it isn't. So it won't, it is just stuck there.

The behavior is the same on all the circuits - tire, suspension jacks, cab. My real pickle here is the fact my cab is stuck sort of halfway. If I were to go crack a fitting and dump the low side pressure, there's nothing to regulate it anymore and I don't see why it wouldn't just freefall and cause damage/death. The way it's sitting it's probably going to fall forwards but it's got a ways to go before it bottoms out. Presumably when you let the cab fall into position some widget is providing the backpressure so that it does not free-fall - whatever that thing is, I am guessing, may be what I have broken or clogged.

Plus, I understand getting high-pressure hydro in your body accidentally from messing with pressurized fittings is outright dangerous.

PS - as an experiment I tried winching the tire crane against the cylinder with all the valves set right. It about lifted the jeep I was using off the ground. I feel like this simulates letting the cab free-fall but seemed less dangerous to try. So I think that if I winched the cab backwards until it passed CG and fell like "normal", it wouldn't. I think it's just going to pressurize the low side and not budge more than a little.

So - Fluid is not getting "out" of the circuits and back into the tank.

It's kind of a lousy situation to be in if only because I don't see an easy safe way to jerry rig it. I would feel a lot better about everything if I could either get the cab full up or full down but it's the halfway situation that is freaking me out. I'm really glad this happened in my driveway and not on some trip.

 

[aleigh]

So I pulled the return line on the tank and with the valves all lined up and under pressure, it only drips. drip drip drip. So I guess either the hose is clogged, unlikely, or there's something gimped with the selector valve in the manifold... If you spin that valve enough you can take pressure off the circuit, but there doesn't seem to make a magic "slightly" position that makes it work.

 

[Lmtv772]

...

 

[aleigh]

I've been through the TMs backwards and forwards. My problem isn't per-say taking it apart, it is how to get it so I can take it apart. Which includes the filters at the top because I cannot be certain they are not pressurized. Or that depressurizing the system accidentally by removing them won't cause problems.

Like I was mentioning earlier, my cab is in an intermediate position. Before I can do anything about the manifold I have to get the pressure out of the system and get the cab either full up or full down - I don't really care which at this point. What I am worried about is if I crack the fittings under pressure without getting my skin injected with hydraulic fluid, that the cab will free-fall. This is because I don't understand if it is the hydraulic ram itself which provides the backpressure so that the cab will settle at a slow speed, or, if it is something else in the system. If the cab will free-fall when I bleed the low-side that's going to be a disaster whichever way it falls. I am easily recalling the story of that soldier who got killed when his LMTV cab fell on him in basically this same situation.

My best bet so far seems to be to setup rigging, off a winch or whatever, to try to hold the cab in place and then to find some way to bleed the lowside. And then I can use the winch to settle the cab down into position. Just eyeballing it I am pretty sure it's going to fall forward.

As I mentioned the TM tells you to bleed the system prior to maintenance but fails to tell you exactly how to do that. I think this is a situation they were not anticipating. It does seem like if I roll all the valves around I can get the pressure out though. Maybe. I say this because if I do it then at each position you can pump easily until the pressure comes up. So I'll probably try that, to settle the system out before I crack a valve.

 

[Suprman]

There are check valves in the manifold.

 

[aleigh]

I think you might have meant 19-20.10 in -20-4. That's the one that details the three little check valves on the side. So you're saying that's what provides the backpressure to the ram, so if I just crack the hoses to bleed them it'll fall?

There are the "cartridge valve" things too. 19-20.12

 

[Suprman]

I don't see why you couldn't carefully bleed the pressure down. If the spare tire check valve is the same maybe you can swap it in place of the cab one.