The day after Thanksgiving i was on my way back to LSU from home which is about an hour drive. My 99 silverado z71 with the 5.3 blew up due to a cracked head. Over the Christmas holidays i did a motor swap, I put an 04 5.3 in her and it went pretty smoothly all i had to do was put my intake manifold and swap the EGR valve off the old motor on the new one. Everything was great until i noticed a huge spot of coolant under my truck yesterday. I have the old water pump but would rather keep my new one from the new motor but here's my question. I took the water pump off and gasket had a slight wrinkle in it, the water pump doesn't have a weep hole so i don't know if i should replace the gaskets because i don't know how to tell if the water pump is bad or not? So, should i replace water pump or just gaskets? If you read all through this i would appreciate feed back

 

I'd replace just the gaskets honestly, go under there and see if the fan can wiggle around. From what I've seen if the fan can wiggle then it needs replacin

 

I would replace both as long as you have it apart. Why do it twice you will never know but why chance it. Just my 2 cents.

 

I wish i still would've listened to your 2 cents ha. I just did the gaskets and it still leaks. It only leaks when at running temp, and i checked the thermostat to make sure it wasn't leaking but its not. I don't know where the hell else it could leak. The fan doesn't shake any ideas of where it could be leaking from. Its hard to pin point it because by the time it heats up from driving it coolant is smeared around. I feel dumb asking but I can't figure it out doesn't appear to leak from hoses or thermostat

 

Well that's odd, did this gasket get crinkled up or cut anywhere? I guess replace the water pump and see what it does

 

Check around your intake manifold, maybe you didn't get it sealed when you replaced it on the new motor.

 

No coolant in the 5.3 intake. Check the 2 hoses on the bottom of the t-body if they are not leaking then replace the pump with a good quality new one. Do not buy the cheapest one you can find.

 

Alright then I really appreciate the feed back, but i do have one more question my truck is a 99 and the new motor is a 04 are the water pumps the same. The one off the old motor is still good, so i just want to make sure they can be swapped. They look the same but just want to be sure.