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2004 Silverado Crew Cab Solid Axle Swap (LLY with ZF 6 speed)

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As I was searching for a water pump I noticed that Sinister Diesel sells one with the gear TIG welded on. That would totally explain why it seems like the pump is working somewhat, but not very good.

I may just pull the existing pump and weld the gear onto the shaft, but I do have an OEM pump that will be here Sunday if my current pump doesn't look so good.
 
r3dd0g said:
I should have guessed it wouldn't be so easy...

I guess I'll order a water pump and see if maybe that fixes it or if I'm just chasing my own f*cking tail.

Fan clutch still doesn't lock up, truck runs slightly cooler (probably due to the thermostats opening earlier) but the temps are still off, 150 outlet temps on the rad, 170 inlet.
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Unless
r3dd0g said:
As I was searching for a water pump I noticed that Sinister Diesel sells one with the gear TIG welded on. That would totally explain why it seems like the pump is working somewhat, but not very good.

I may just pull the existing pump and weld the gear onto the shaft, but I do have an OEM pump that will be here Sunday if my current pump doesn't look so good.
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Hope that’s your problem?
A lot of work if not.

What is the temp outside where you live? Our trucks hardly ever run the fan. But we are Alberta you are Arizona.
 
It's about 105°F today. I believe when I had my truck tuned they raised the rev limiter (I had asked them not to, but that didn't happen). I guess this is what causes the impeller or drive gear to slip.

There are some companies that sell welded ones, but then they started having issues with the welds cracking so some companies started pinning them instead... Apparently AC Delco quality is so sh*t now that they don't pin them any longer as they would fail anyways. The current fix is to "upgrade" to the LBZ or LML (can't remember) water pump but that requires a special housing. Those pumps have a lightweight resin impeller that won't slip on the shaft.

I'm learning way more about this stupid cooling system than I want to.
 
r3dd0g said:
It's about 105°F today. I believe when I had my truck tuned they raised the rev limiter (I had asked them not to, but that didn't happen). I guess this is what causes the impeller or drive gear to slip.

There are some companies that sell welded ones, but then they started having issues with the welds cracking so some companies started pinning them instead... Apparently AC Delco quality is so sh*t now that they don't pin them any longer as they would fail anyways. The current fix is to "upgrade" to the LBZ or LML (can't remember) water pump but that requires a special housing. Those pumps have a lightweight resin impeller that won't slip on the shaft.

I'm learning way more about this stupid cooling system than I want to.
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I can see why your concerned, 105 haven’t seen that much in my life but the fan would be running for sure.
 
I have the think back to a truck we had in the shop last summer. I think it was a LLY, mint dual my truck with under 100k on it.

Issue was it needed something very basic (don’t recall what it was) but after we touched it the damn truck would start ringing the overheat alarm running up to 240-250 degrees. So out came the parts cannon and my tech fired with both barrels having replaced the t-stats, water pump and new cap. Still did it.

But I noticed a pattern that picks up on what you mentioned about the impeller spinning on the shaft. I was buzzing the truck up a good sized grade out of town. The customer noticed it only overheated with a load/trailer on it. Not wanting to hook up to a trailer every time we thought we were done I just lugged it in a lower gear to keep the load up at the same speed. Sure enough with it in third it would overheat without the trailer.

I had a temp gun and I was pulling over and taking readings at the hoses and both sides of the radiator as well as the t-stat housing. Let the truck idle as I checked and the temps fell right back in line. I don’t remember the numbers I was getting but I do think it was along the lines of a slipping impeller.

Turned out the tech improvised on the water pump replacement and got an aftermarket unit because we were a couple days out on the correct oem part. When I found out this tidbit I said maybe we stick with the oem stuff and had him get the housing too. The housings can Get eroded out over time and reduce the pumps ability to push fluid.

Gm pump and new housing was the ticket. 4 horse trailer with full living quarters up the same grade in 90 degree temps never went past 220 degrees.
 
The issue is, AC Delco makes the OEM pumps and they're crap now. I just put an AC Delco Professional pump in back in 2019 and it's slipping.

Also when I did all my temp tests I shut the engine off as soon as I stopped so I could get more accurate readings.
 
I’m not surprised quality on all things gm has gone to crap. We did that one last year and it made it far enough to not come back. But who’s to say if that pump slips on the customer this summer. Happy I’m not there to find out.
 
I put the new AC Delco OEM pump in and it seems like everything is working right now. I even put the OEM fan clutch in and it's locking up when I stop if coolant temps are close to 200.

What a pain in the a$$.
 
You can see on the pump I removed that it looks like the impeller slipped further onto the shaft and also it looks like the tips of the impeller blades were touching the housing (although I didn't see any damage on the housing).

IMG_20220530_154008506.jpg


If the OEM pump slips I'll order one of the upgraded pumps next time.
 
fastazz81 said:
It’s pretty simple it has a cover you pull and insert a lock . I found it a pain to get the o rings on the plumbing above the pump not to leak.
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I had just replaced all those o-rings when I was doing the head gaskets. I just unbolted that tube from the pump and left it inserted into the crossover pipe.
 
Well, the drama continues. Now that I've driven it a bit I'm realizing something still isn't right. Once the temps heat up past 200, it really doesn't want to cool back down and will drift right up to 225 again.
I've got 3 different fan clutches that all behave similarly.
-The brand new AC Delco OEM Fan clutch, it locks up after you park it and will also lock up if you stop the truck and idle at over 205, but it really won't lock up unless you slow down. While driving up to Payson (no trailer) we saw 228 before we let off and got the fan to lock up. Even when the fan locks up temperatures don't drop dramatically like I would expect (like they used to).
-The old Hayden one that was working fine right up until it stopped locking up (what I thought was the original problem), it behaves almost identical to the AC Delco one.
-The old NAPA fan that used to lock up around 200 and was super annoying to use on the trails as it was constantly locked up. This one works the best, but still really won't lock up fully unless you stop, then it unlocks as soon as you rev up the engine.

It really seems like the water pump is slipping again already when it gets hot, which would be very annoying. I'm really out of ideas and tired of throwing money at this problem.

The water pump had a paint line across the shaft and impeller, so I should at least be able to tell if it was slipping.
 
I decided I was going to disassemble it, already found a bunch of steel on the magnetic drain plug for the radiator, way more than last time I took it apart so I think I'm on the right track, albeit a frustrating one.

The weird thing is, most of the sites say this shouldn't be an issue unless you're pushing over 4000RPM which I'm not...

I think I'm going to try my hand at welding the old one myself (I'll return the one that's in it currently). This will at least let me drive it around enough to find out if that fixes the issue.
 
Here's what the drain plug looked like, way more metal than I've previously pulled out of it.

1655066042702.png

But when I pulled the pump, I'm not sure it actually looks like it was slipping.

1655066096775.png

The paint stripe is still lined up, but the shaft is slightly recessed into the impeller and it looks like the pump has contacted the housing like the old pump.

I welded my old pump (submerged in water except the top of the shaft/impeller) and installed it temporarily just to test.

1655066229137.png


We took it for a test drive (the NAPA fan clutch was reinstalled), it seemed to be a little better, but it still got up to 221 once (112 today for reference). The fan clutch still doesn't lock up while driving, only when you slow down or stop. Also now the "Coolant Temperature High" alert on my dash comes on at 219, which I've not seen previous to today, even when it was above 225. I'm ready to just light this stupid truck on fire.
 
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