M998 Noise issue

[Skitrman]

Trying to get some help locating a noise on an M998. It originally had the 6.2 but was swapped by the refurb people to a 6.5 when it was overhauled. Right now I have an intermittent noise coming from under the dash on the drivers side. The sound gets loud thens basically disappears every couple of minutes. It sounds similar to like a heater motor bearing is what I would compare it to. My understanding though is the heater motor is on the passenger side so I don't think thats what it is. I haven't been able to isolate it as of yet. Has anyone had anything similar?
On a second note, what type of lube does everyone use on all of the different lube points?
Thanks for the help.

 

[BLK HMMWV]

open the hood and feel the Cadillac valve with the engine running.

 

[teteacher101]

Trying to get some help locating a noise on an M998. It originally had the 6.2 but was swapped by the refurb people to a 6.5 when it was overhauled. Right now I have an intermittent noise coming from under the dash on the drivers side. The sound gets loud thens basically disappears every couple of minutes. It sounds similar to like a heater motor bearing is what I would compare it to. My understanding though is the heater motor is on the passenger side so I don't think thats what it is. I haven't been able to isolate it as of yet. Has anyone had anything similar?
On a second note, what type of lube does everyone use on all of the different lube points?
Thanks for the help.

Does it sound kind of like a hiss? If it does then its probably the Cadillac Valve.

A lot of people will want to say "refer to the TM" for fluid info an frequency and you can definitely insue a which fluid brand is better debate much like the "Ford, Chevy, Dodge" debate but the most important thing is the fluid just gets changed with the correct species and quantity an checked after that on a regular basis. Frequency of changes is dependent on where and how much you drive it.

Personally I use 15w40 diesel oil in the engine, Dexron in the tranny an t-case, power steering fluid for well the power steering, Dot 5 for brake fluid, 80w90 in the diff's and hub's, an all purpose grease in my grease gun for all the zerks.

I am not someone who gets hung up on brands, synthetic vs. non-synthetic, etc., etc. That's a personal and wallet preference.

 

[Milcommoguy]

Likely the Cadillac valve (on a HUMMWV?) used to control the fan clutch. It's the normally golden color, round thingie out in front of the windshield, under the hood, drivers side. When by-passing fluid thru internal design, makes a hyper sonic "hissing" further amplified by where / how it is mounted. Can be reduced by remove and wrapping with a piece of damping material ie 1/8 rubber or cork.

Normally not heard a cruse speed or anything else. LOL

TM states... power steering to use Dextron II. Same as in the three speed transmission TH400 and transfer case.

Here's a easy read for a lot of question on HUMMWV.

http://www.survivalebooks.com/free ...il. Multipurpose Wheeled Veh. (HMMWV) 60p.pdf

Use the red stuff,

CAMO

 

[Skitrman]

Thanks for the reply, I will check it today before the snow starts again. I'm not sure if that is it or not. As I originally stated it's not what I would necessarily call a hiss as much as a rotational intermittent wine. I'll post again later if I determine it is the Cadillac valve. If it is the Cadillac valve does it need to be replaced or? Milcompany said the Cadillac valve controls the fan Clutch so is it an electrical switch or does it have fluid passing through it (as being a valve would indicate)? Fluid should be good but I'll check that again as well.

Thanks for the suggestions and help from everyone so far.

 

[NormB]

Question is, really, with all that other godawful racket from the engine, how can ANY of us hear that hissing?

I got wrapped around the axle over this a month or so ago for a few moments. I’ve owned my M1038 going on 2-1/2 years and that was the FIRST time I heard the hissing from under the dash - from the cadillac valve.

I woundn’t have given it a second thought had I not already read something about this here a year ago or so plus I had to replace my valve not long after buying the truck as it had died. Worked when I bought it, then winter, then spring/summer, no fan.

I’d already bought a spare. When you see them on fleabay from the guys who buy spares by the pallet load at auction selling some of their stock and the price plummets from the usual online parts supply house $185 to $75-100, get one.

You may never need it, but better to have it and not need it. I used mine (and bought another. Cheap insurance).

 

[Milcommoguy]

If one has good hearing? you also could hear the alternator "whining" or "singing" under a charging load at varying RPM's. This is due to the three phase stator windings - magnetic field inducing this AC components into a loose laminated stator core parts. Could sound like something turning at varying RPM's... But you have to listen closely. (not a big deal) Many times a bad diode/s or regulator will get it to really whine. AND then it could be a bearing or...???

Now that could be a big deal,

CAMO

 

[Skitrman]

If I can figure out how to post a video clip I will record it when it happens again. I have an 8' Meyer Lot Pro Plow on mine that is a year old. I don't think it has anything to do with it though. I started it up this morning and let it get up to operating temp and it never did it. It seems to only do it while driving/plowing but as I said originally, it is intermittent and the sound is definitely coming from under the drivers side dash.
Thanks

 

[Skitrman]

Here are a couple of Pics of the HMMWV. If anyone knows anyone looking for a nice one it is for sale. Titled and plated in Wyoming.

 

[warcow105]

With all of the noises my truck makes I have no clue what's normal, just that it still runs fine. Until it dies I'm just going to assume that cacophony of loud noises is normal lol.

Mike

 

[1 Patriot-of-many]

This has been covered before, wrap a rubber insulator like inner tube rubber around the Cadillac valve. The hissing sound disappears according to all the posts.

 

[RJTM998]

This has been covered before, wrap a rubber insulator like inner tube rubber around the Cadillac valve. The hissing sound disappears according to all the posts.

Dragging out an old post but the rubber inner tube trick solved my hissing noise. The hissing was driving me nuts. I love all the knowledge on this forum.

 

[Mogman]

Here are a couple of Pics of the HMMWV. If anyone knows anyone looking for a nice one it is for sale. Titled and plated in Wyoming.View attachment 754032View attachment 754033View attachment 754034

Put it in the for sale classifieds in the forum.