Homeowner replacement of a Grundfos pump

[Chicago Al]

I'm a homeowner (and former owner of a small apt building) with zero training, but I can figure out how to DIY a lot, and this forum has been amazingly helpful to me in many such tasks over the years.
We have a hot water boiler in our house, a 15 or so year old Triangle Tube Prestige, which has had some work done but has actually been okay for us. The house is only 1600 sf and has two zones, both with Grundfos 15-58 pumps inline.
The pump for zone 2 is noisy and has been so for several years. It sounds like...well, like a motor with bad bearings, like a jar full of marbles swirling around. It has not gotten worse over time but eventually it'll go out and in the meantime it's annoying as the sound travels through the pipes.
I just got a price of just under $1000 to R&R the pump from a local HVAC company, same one as has done a couple of 'annual maintenance checks' for us. That seems like a lot considering I can see the pump sells for $130 even to retail customers.
So I'm very tempted to replace the pump myself. There are valves on either side of it, there are four bolts, and the electrical is simple enough (I re-ran the wires from the Taco control box to our thermostat last year).
Would this install be as simple as it looks or am I potentially letting myself in for a world of hurt? Would the whole system need a flush or to have the air bled out after this? (I have no idea how that works as we never do it.)
Thanks for any advice and for reading this far!

 

[Breplum]

The pump swap is very straightforward with the valves in place at the flanges. Bleeding air can be tricky.
You likely want to own a large, flat head screwdriver to help the flanges separate and of course new flange gaskets.

 

[Sponsor]

 

[Bgard]

I would not remove the pump from the flanges! Just remove the four Allen head cap screws that hold the motor head assembly to the valoute, turn off the isolation valves on each side of the pump first, this is an o- ring seal and very simple to do, leave the four cap screws just a little loose, turn the supply side valve on a little and the water should purge the little amount of air out, when water comes out tighten the cap screws down and open both valves, turn the pump on for a few minutes and the air purger in the system wil remove any air remaining.

 

[Breplum]

Yup, I understand now. Sounds like a worthy approach.

 

[Chicago Al]

Thanks Bgard! I don't see the motor for this model (Grundfos 59896341 P1) being available separately, but the whole thing is less than $150. If I understand you correctly, this method would save having to mess with the flanges, the wiring, etc. I like this idea!

To make sure I've got it right:
1. Get the new pump, but remove the motor body from it (four allens).
(Turn boiler and power to pumps off)
2. Shut the isolation valves and remove the old motor body from the pump.
3 Install new motor but leave the four allens slightly loose.
4. Open lower isolation valve slightly, till water fills the pump.
5. Tighten the allen screws.
6. Restore power to pumps and boiler, boost thermostat so system goes into heat mode for a while to test and for air purger to work.
7. Bask in the admiration of my adoring wife. (Hopefully)

I have to read up on purging air; we never do that on our system and it works great (with the exception of this noisy pump) so either it doesn't take on air or the air purger handles it. I'll look into that, I should know about it anyway.
I really appreciate the advice!

 

[Breplum]

Yes, should go well.

 

[Fitter30]

Turn boiler off and controls. Close the valves when cool, take pic of back of pump change pump and gaskets. Like for like. Open valves.

 

[Bgard]

Yes that is the procedure