Can anyone actually explain what goes on in a Diesel engine that makes that familiar rattle noise? Why is it so loud when it's cold??

Detonation Clatter is most of it, atomized diesel fuel combusts very rapidly. The cold rattle is advanced timing making the detonation more pronounced to help the engine warm up faster. The injection pump/injectors themselves make quite a bit of noise too, mostly because of the high pressures they operate at.

Yep - and that sound like a ball pein hammer in the 6.2\6.5L cylinder heads is that extreme rapid-oxidation causing the indirect combustion chambers (pre-cups) to bang around inside their little cubby-holes in the heads.
Can be rather disconcerting on a chill Winter morn.........

Cummins and Navstar are direct injection, and give only the normal 'tinny' Diesel rattle of rapid-oxidation between cast-iron heads and aluminum piston crowns - a suh-weet sound, at any juncture............

Has anyone yet removed the dampening stuff that sits on the underside of the hood? I wonder what sound that would make and if I should do it ...

The thermal insulation on the underside of the hood?

I have heard, but can not confirm, maybe TDG or someone else can help with this, that the HUMMEV's (miltary Hummers) don't have the heat problems, ie.. PMD..., that we have. I don't know if they use the thermal insulation banket of if they do something else to get the underhood temps down?
Just what I heard don't know.

Up till very recently, HMMWVV's got the mechanical injection pump - no EFI, no FSD\PMD.

AWWW Well that might explain that then I guess

The thermal insulation on the underside of the hood? Yes, I mean the stuff/fabric or whatever it is on the underside of the hood. It can act as thermal insulation as well, though I think it is supposed to lower the sound of the engine. QM, I can imagine that you removed it to lower underhood temps in the hot area your living --- does it make a difference?

Hmm, I'm going to install new washer nozzles in the hood, and the insulation will be in the way. I can as well try to remove it when I am at it --- maybe this way, I can get some warmth to the nozzles so that they don't freeze or are defrosted once they are frozen :)

The nozzles were not easy to come by, and I couldn't get heated ones that wouldn't require making large slots into the hood.

Geez, what are you trying to do? Wash the whole truck with windshield washer jets?

Hehe :)

I'm not sure yet if all of them will be installed. Three of them make two jets, and 4 of them make one jet.

The story behind it is a bit long: Ever since I own the truck, the wipers and the washer nozzles were not fully functional. It turned out that the tube going to the nozzles was rotten so that most of the water dripped out at the bottom of the fender in front of the wheel on the drivers side, instead of going to the nozzles. To get at the tubing, the inner fender had to be removed, and the battery had to be taken out. A short piece of tubing that goes under the battery to the water reservoir wasn't rotten, thus we were able to route a new tube to the stock nozzles. We tied the new tube around the large engine-coolant tube so that the water will be warmed before it comes out of the nozzles.

But the nozzle on the drivers side turned out to be somewhat clogged and that none of them sprayed very well. Somehow, the drivers side nozzle got broken during our attempts and things didn't work as well as they should.

At the same time, we removed the wiper motor, cleaned out its gears and put new grease to them. The wipers were sometimes functional, sometimes not, and the problem became worse and worse over time. I had been asking around about the wiper problem here --- QM suggested to replace the wiper motor, but they're asking about $250 for it ...

Meanwhile, I aquired some washer nozzles from a junkyard and managed to tie them to the plastic grating that sits in front of the windscreen with wire straps. They look ugly and sit quite loose, but they're functional.

Cleaning and greasing the gears of the wiper motor didn't help. At last, I found that the wiper relay (the blue one) is broken. We rewired the wiper motor, and now it wipes faster than ever before. But by removing the circiut board that usually sits inside the gear-case of the wiper motor, I became unable to spray any water because the water pump was disconnected.

I was very happy that the wipers finally were functional, but after two days on slightly wet roads with a windscreen getting ever more dirty, it became a real PITA that I couldn't see anything through the dirty glass ... One just cannot stop frequently enough at gas stations where they have water for cleaning. --- That kind of dirt is wet when it comes onto the windscreen, but there it dries immediately so that you cannot wipe it off.

To make things worse, each morning when going to work, I'm headed directly against the sun on a small, curvy and dangerous road for the last 5 miles. The sun is shining onto the wet road and its reflection blinds you, and it shines onto the dirty windscreen and blinds you even more, and you can't see anything unless you clean the glass. But you cannot clean it without water ...

On the afternoon of December 24(!), I put out the battery on the drivers side to get at the wire that goes to the water pump. There's a plug in the wire where the battery is. I routed a new wire from the plug into the cabin to a switch. That way, I can turn on the washer pump.

That went very well, but the water pump now runs faster than ever before (the stock wiring sucks, not only there), and water sprayed out of the tubing where we had put together the old tube and the new one. Thus, it was leaking again :(

I fumbled around for hours, in the darkness, until I found something to put the tubes together that wouldn't leak.

Now, what's left is installing new washer nozzles and do a better rewiring of the wiper motor. Then, after more than 1-1/2 years, I'll finally have these things working! It gives me a wiper without interval that I can stop in any position I want and a washer pump that I can turn on and off whenever I want.

The new nozzles should be installed far enough to the front so that they spray the water onto the windscreen while the wipers are in the down position. That way, I can wait for the water to soak the dirt on the windscreen before engaging the wipers :) Some more water helps some more, but the point is that the windshield is quite wide so that I need something to distribute the water all over it.

Usually, nobody cares about the wipers and the washer system because they just work. Only when these things fail you come to know how important they are.

Aside from that - did you try resoldering all the connections on the relay board, and the connector board in the motor housing, including T4-T5-T7, relay, etc?

The rotted hoses are bad enough, but the relay board solder joints are not NASA quality, and often open, adding to the problem(s).

Re-flowing the solder usually recovers the functions.

The connections on the board seem ok. The relay was making a noise as if it was switched on and off very rapidly.

For a long time I thought the noise came from the wiper motor in its attempt to move the wiper arms which appeared to be sticky for unknown reasons. After ruling out sticky wiper arms and sticky gears, I asked around a bit and got the suggestion that the brushes of the wiper motor could be sticky, while my idea was that it didn't get enough current for unknown reasons.

At some day when I came home from work, the wipers stopped working just when I arrived. I opened the cover of the gearcase of the wiper motor and immediately found out that it was the relay making that noise, not the motor.

I took the board off and measured the connectors. While measureing, the relay didn't make the noise but clicked normally when switching on and off. I put the board back on and the relay rattled again. I routed some wires from the battery to the connectors on the wiper motor, and it ran fine.

Not having the interval is a disadvantage, but being able to spray water without the wipers moving is a nice advantage. Also, I can turn on the wipers whenever I want, without the engine running or accessory power turned on. Stopping them in the position I want them is another advantage --- I got used to turn them off in the down position (or anywhere else) very quickly.

Thus, I don't care about the board anymore :)

a self washing truck?

Ja, a self washing truck :)

I've removed the underhood fabric, and now I can hear more of the beautiful sound of the 6.5. The fabric makes quite some thermal insulation, too --- after driving 30kms and sitting for 10 minutes or so while I was filling the tank, the hood was noticeably warm which it didn't get before (it's about freezing outside).

I think removing the insulation can help well enough in lowering the underhood temps to make removing it worthwhile. But it's more or less a one-way thing to do because the fasteners that attach the fabric to the hood break into half before you get them out. I ended up cutting them off with a wire cutter. The fabric can be reinstalled with some kind of replacement fasteners, though.


The heat will help defrosting the new washer nozzles :) I installed two of them today so that I've 4 jets now, and I'll probably install at least two more for some 'fine tuning' the jets. These nozzles are great, they put loads of water on the windscreen and actually deserve their name _washer_ nozzles.

If you can get some of these and have some time to spend, install them. You can do that even with the stock tubing. Also, rewire the washer pump --- it's easy enough and turns it into something like a high-output pump.

I'll add some pics on Friday or so.

I think that keeping a blanket on the hood in the winter could make removing the thermal layer possible(it does freeze here!) but most of my under hood heat is from running the A/C when it's warmer outside like today. Last week it was 25F high today was 70 F

Is the insulation or a blanket really needed to keep the engine warm? When it's turned off, it gets cold anyway, when it runs, it makes enough heat, and having the insulation removed can contribute to keep the intake and eventually the IP and the PMD a few degrees colder.

Maybe the insolation is a good idea when it gets to 0F and below or when idling the engine for extended periods of time. But then, something thicker and more capable of blocking the heat would be better.

I've put some insulation into the back of the cabin this week, 1.6" of so-called 'Styrodor' (kind of hard foam) plates covered with a plate of 0.35 inches of hard wood. It makes for a very nice surface to put things onto and a difference in temperature. Where I've been driving with the blower switch in II, I now can keep it at I. Maybe I'll try to insulate the rear windows, too. It takes ages to get the cabin warmed through when it's cold outside, and the back always remains quite cold. The insulation does help that :) I think it will also help the AC in summer by keeping the heat out and the cold in.

I believe that blanket is more for noise control, to produce a "quieter" diesel truck.

Washer Nozzles

The blue wire right to the battery supplies the water pump. The tube for the washer nozzles goes around the large coolant tube a couple of times so that the water is somewhat heated before it gets to the washer nozzles. I still need something better than the adhesive tape to fasten the tubing under the hood.

nice job now where did you get those nozzles at?

Thermal insulation

THX! I've got the nozzles from a local Bosch-Service. He couldn't find a price for them, so I got them at a very good price. They're sold out now ):h<g>

For reference click here (http://www.vdo.com/siemens/en/prod_washer_nozzles.asp) --- you can also download a catalog (http://www.vdo.com/siemens/sycomax/uploadpool/documents_GBR/download/PDF/Screen%20all_UK.pdf) from there.

Here's a close look at a nozzle:

</g>

Switches in the cabin, left one turns on the pump, right one the wipers. I'm not sure if they will stay there or be relocated to somewhere else --- I used to keep my ashtray where the switches are and can't find a better place for it ... The stock ashtray sucks, you need to lean forward to get at it and never manage to extinguish the cigarettes in it.

These switches are great, aircraft approved and water proof :) They'll probably never fail. The wiring will be changed when the new batteries get connected --- they're installed behind the front seats, 2x135 Ah. (The rear bench is removed.)

Olee did you ever contact your Chevy dealer to have the wiper motor (and electronics) replaced? They are under recall by Chevy for the exact problem you were having intermitant function. I received my notice about six months ago but haven't ever had problems with mine.

[QUOTE=0lee]Yes, I mean the stuff/fabric or whatever it is on the underside of the hood. It can act as thermal insulation as well, though I think it is supposed to lower the sound of the engine. QM, I can imagine that you removed it to lower underhood temps in the hot area your living --- does it make a difference?

Hmm, I'm going to install new washer nozzles in the hood, and the insulation will be in the way. I can as well try to remove it when I am at it --- maybe this way, I can get some warmth to the nozzles so that they don't freeze or are defrosted once they are frozen :)

The nozzles were not easy to come by, and I couldn't get heated ones that wouldn't require making large slots into the hood.

:D For the heated washer fluid, lengthen the washer supply tube and wrap it around your radiator hose. The more wraps you take around the hose the better. Of course this only works when the truck is warm....

):h I have no heat shield/ insulation under my hood. I have to say that it's pretty LOUD.

Olee did you ever contact your Chevy dealer to have the wiper motor (and electronics) replaced? They are under recall Thanks for the hint! But we don't have Chevy dealers here, at least not in that sense. There are a very few GM (i. e. Opel) dealers here that sell Chevys, but they are not very helpful. I even doubt that they get informed about such recalls --- or, if they could get informed, they are not interested in them.

One of them is about 40 miles from here, but it's of the kind of shops you want to avoid by all means ...

Anyway, if I could find more information about that recall, I might become able to convince them to give me a replacement motor. I would keep it as a spare to put on in case the current one totally fails --- I like the current setup more than the stock one, except for having no interval.

:D For the heated washer fluid, lengthen the washer supply tube and wrap it around your radiator hose. The more wraps you take around the hose the better. Of course this only works when the truck is warm....

):h I have no heat shield/ insulation under my hood. I have to say that it's pretty LOUD.
Ja --- I'm still lacking some vent to block the water from flowing back into the reservoir. Thus, most of the water doesn't stay in the tubing and doesn't get so hot.

With the insulation removed, it's louder, but mine is not very loud since I found the cause of the squeaking I had and removed it. I'm not sure if I'll reinstall the insulation --- it greatly helps to reduce the temperatures under the hood.