So, I had what I thought was a reputable shop swap out a crankshaft in my 4.08 LS engine. When they first fired up the car (I was there to witness) it didn’t really have much coolant in the engine, I saw him add 1.5 gallons of coolant after the engine thankfully shut off before it seized up. My question is if you run the water pump without a sufficient amount of coolant will if fail? I have the car back now and it is overheating now. I tried for about a half hour to get any air pockets out of the cooling system, I do believe that there isn’t any more air in it. While trying to bleed I noticed when I had the rpm’s at 1500 to 1800 hundred the temperature would start to drop a few degrees and when I let off it, it would rise again, so it seems to me that when the water pump is spinning faster the temperature drops . This to me seems like a damaged water pump. What do you think about this issue?

 

You need a new "reputable" shop. These *** hats shouldn't be working on anything but maybe replacing light bulbs in a lamp....

 

So what is hot temp wise? What does the temp gauge show? My Silverado runs day in day out at 205-210 degrees.
I believe the water pump has sealed bearings so it does not require coolant for lube. Can't believe it matters to the impeller if there is coolant in there or not.
I read you think you have all the air out but it can be a bit tricky. I finally broke down a bought one of those vacuum radiator fillers things for my LS swaps. Got it from HF for about $80? Works great.
Have checked the thermostat and what temp is it? When I replace a LS thermostat before I install it I drill 3 1/8" holes in the flange part to get a bit coolant flow before it opens.

 

As far as the temp goes, before I brought it to these guys it ran at about 190-200 degrees, even in hot weather. Before I tried bleeding it, it got up to 240, at that point I shut it off. Started bleeding it and got it down to 220, but while trying to bleed it I raised the rpm up to 1500-1800 and the temp would drop a few degrees. It seems that spinning the water pump faster drops the temperature. I’m using a 187 degree thermostat. Also the only thing that has changed is I am now running VR20-50 rather than 10-30.

 

‘Why would you put 50w oil in an LS engine? 50w oil is for dump trucks. Oil flow is required to properly keep your bearings cool and oiled….50w is much too thick. Higher weight oil does not protect better, but will likely hurt the engine long term. 30w will bleed off bearing heat much better than 50w in an LS platform. Unless this build has rather large bearing clearances, dump the 50w and get 30w back in it. That’s step number one.
The shop that ran the engine in with low coolant has me puzzled as to why. If the upper cylinders and heads are not surrounded by moving coolant, the heat transfer can not take place and piston skirts, piston domes, valve guides, valve stems, and headgaskets all get very hot, very fast. You’re right with your seized comment. I’d be concerned right away with headgasket seal. You’re gonna have to do a pressure test on the cooling system first. That will give you an indication of headgasket condition. I’d then have to wonder if the rings aren’t hurt, and do a compression test second. Man shops that let their mechanic staff do stupid stuff like this **** me off. Zero reason to put coolant in the engine later, rather than beforehand. Running it for a minute or so isn’t a big deal, but if they ran it for several minutes, a gallon and a half low, while new….oh boy.

 

Spinning the water pump impeller faster is exactly what engineers do if an engine is running on the hot side during development.

 

So they let the engine get hot hot hot, THEN decided it was down almost 2 gallons of coolant, so they dumped 6 quarts of coolant in it??! On a new engine? WOW!! That's like tightening a bolt til it starts stripping the threads, then you back it off a 1/4 turn!! You need a new shop. Even an average quality shop would be miles ahead of the ***-hats that did this. Id be mighty pissed off if I were in your shoes. Sheesh!!!

 

Also, running 50wt oil in an LS engine isn't a good idea, unless you're road racing it at high rpm, and are seeing 275°+ oil temps. Thicker, high viscosity oil actually runs hotter than thinner, low viscosity oil. Run 0w-40 Mobil 1, or equivalent....

 

Thanks for the advice.