I did the water pump on my 2006 Envoy Denali with the 5.3 this weekend. It was not that fun. I have done the same job in the last month on my 1999 Suburban with the 5.7. Here are some comments you may find helpful.
The ACDelco 251-743 Original Equipment Water Pump with Gasket:
This fancy new GM pump looks like a piece of jewelry. Almost too nice to put under the hood. The part listing says you need to buy a new water neck (ACDelco 15-11057).
The new pump comes with new gaskets and two new bolts that will fit the new water neck. The water neck comes with a thermostat (which is not really clear from the part listing). I think if your water pump is an original factory unit, the water neck is different and has an integrated non-replaceable thermostat. So the new pump has the two new bolts that will fit the new water neck (now with a replaceable thermostat). If you are changing the pump, you also want to change the thermostat.
The water pump part listing also says you need a $6 – part number 15-75247 bolt. I did not need this bolt, but I did spend the $6 for it – yay.
After doing both jobs within a month of each other I have concluded the Suburban was very easy (with the help of a YouTube video of course). The Envoy is much more difficult.
There is a video on Youtube that is very good - you basically following approach in this video.
https://www.youtube.com/watch?v=7twQRCTv45U
Step 1: Empty the coolant
On the Suburban you can siphon out the coolant since the radiator cap is on the end of the radiator. This lets you put a small siphon hose down the side of the radiator to the bottom. Only a little coolant spills out once that is done. Piece of cake job, no fuss, no muss – only a little coolant spillage when the pump is pulled off.
On the Envoy, the radiator cap is in the middle. No easy way to siphon the coolant. You have to pull the lower radiator hose. It’s messy and you will take a bath in coolant if you are not very careful and patient. The larger the pan you use, the better. I did not see a drain petcock on the Envoy radiator, there may be one – I did not see it.
Tip: there is a small L-shaped metal plate that will block the lower hose from being removed – two 13mm bolts hold this plate to the frame. You will want remove this plate to get that lower hose off.
Step 2: Remove clutch fan
On the Suburban there is a fan removal tool (a long thin metal bar) that can hold onto 2 out of 4 fasteners on the water pump pulley. With the tool in place you can also can get a big 12” adjustable wrench on the fan nut. You hold the fan tool (and pulley) still and break the fan nut loose. With that fan tool, the job is piece of cake – a 2 minute job.
On the Envoy, there are no fasteners on that water pump pulley. So there is no easy way to hold the pulley other than the drive belt – which does not have enough grip.
Tip: put the adjustable wrench on the fan nut, press down hard on the belt. I used the head of a hammer (inverted) to press on the belt. Then you strike your adjustable wrench with a 2nd hammer. Three hands would be ideal. Otherwise, this is tough maneuver and that fan nut is not going to go easy. After about 20 minutes (after you hit yourself with the hammer a few times) the fan nut will break loose – not fun.
Step 3: Remove upper hose. A hose pick tool is very helpful here. Those GM hose clamps are a tough deal. They are actually molded/tethered into the factory hose and cannot be slid up the hose. They do lock open, but they are not fun to deal with. I think there is a tool for this as well – this would probably help.
Tip: you may want to just forget about the factory upper and lower hoses. If your truck has like 100K+ miles and you are doing a water pump, you might as well just cut the hoses as needed to get them off. This is a good time to put in new upper and lower hoses anyway. You don’t want to do this job again for as long as possible. Remember to get new clamps with your replacement hoses.
Step 3: Remove fan shroud and fan together
On the suburban the fan shroud is two pieces. The upper part is held on with 4 bolts and then it can be removed (don’t forget to remove the little transfer case vent hose as well). With the two piece fan shroud, the job is piece of cake – again a 2 minute job.
On the Envoy, the fan shroud is one piece with just two bolts at the top. There are two plastic locating pins molded into the shroud that engage holes in the lower radiator support. The fan shroud and fan have to be lifted out and removed together as a unit. After you remove the two bolts (and an electrical connector) that shroud will not want to come out.
Tip: the fan shroud is also secured with some … flexible polymer sheet material … down low on either side. Each flexible sheet is held on with two small tabs. You need to release these flexible sheets before the shroud will come loose. There is not much room in there, but you can get that stuff released. Once this is done you can work the fan and shroud out. It has to be pushed past the upper radiator hose fitting on the left side but it will come out.
Also, the Envoy has two metal transmission cooler lines that are actually snapped into a double clip that is molded into the lower portion of the fan shroud. Those lines have to be carefully pried out of that molded plastic clip.
Tip: use a heat gun to warm the plastic clip area so the coolant lines can be pried out with minimal force.
OK, at this point you are in good shape – sort of. The remaining steps are pretty simple.
Step 4: Remove serpentine belt/tensioner
The drive belt is easy to remove – just use a wrench on the tensioner. The drive belt tensioner has three bolts that hold it to the pump.
Step 5: Remove lower hose from the water pump.
Tip: just unbolt the water neck and leave the hose and clamp attached. You are buying new hoses and a new water neck. So you will probably be throwing the water neck and lower hose in the garbage anyway.
Step 6: Remove heater hoses from left side of pump.
These also have those GM spring clamps molded to the hoses. You will be re-using these hoses. Luckily they are small and can be worked loose. A hose pick tool is very helpful here.
Step 7: Remove water pump:
There are 6 bolts holding the pump on. They are all the same size. They are not very tight.
Step 8: Re assembly
At this point it’s just a simple matter of cleaning up the gaskets and reversing the process to install. Not a big deal. Follow all the torque values for each set of bolts. The water neck is 11 ft-lbs. Those 6 bolts holding the pump to the block – two passes – 1st pass 11 ft-lbs, 2nd pass 22 ft-lbs. The three bolts holding the tensioner – 37 ft-lbs. Don’t just hammer the things to 400+ ft-lbs with your air tools – no good can come from that.
Step 9: Bleeding - literally
I don’t know what to say about this. I did the job and then started the truck. No heat and the temperature started to climb over 220 … I shut down the truck. In the Suburban, I never had any problems getting the system bled. You leave the cap off and then the coolant flows.
The Envoy never bled itself. It was very clear that coolant was not flowing. There is a vent hose that is attached to one of those heater lines on the left side of the water pump. It connects to a pipe sticking up vertically out of the intake manifold under the throttle body. I removed this hose to “vent” the system – and no go.
I ended up draining the truck and removing the thermostat. I had a spare thermostat so I swapped that in. I refilled the coolant. This time I left the vent hose off – I heard it whistling as I filled the radiator. Started the truck … no heat and the temperature started to climb over 220 – Yay!
So now I know it’s not the thermostat (two in a row can’t be bad). Either the pump was bad (not likely) or the system is still not bled. So I made sure the truck was cool and took it for a short drive. Once it warmed up I mashed the gas pedal … and wait for it … the heat came on. The truck was happy after this. Revving the engine got that coolant flowing. So other than this “procedure” don’t ask me how to bleed this system – mashing the gas pedal is probably not the right way.
So if you want to do a water pump, these are the things you need to know. That video is really good and gets you most of the way there. These tips should save you some time as well.
The ACDelco 251-743 Original Equipment Water Pump with Gasket:
This fancy new GM pump looks like a piece of jewelry. Almost too nice to put under the hood. The part listing says you need to buy a new water neck (ACDelco 15-11057).
The new pump comes with new gaskets and two new bolts that will fit the new water neck. The water neck comes with a thermostat (which is not really clear from the part listing). I think if your water pump is an original factory unit, the water neck is different and has an integrated non-replaceable thermostat. So the new pump has the two new bolts that will fit the new water neck (now with a replaceable thermostat). If you are changing the pump, you also want to change the thermostat.
The water pump part listing also says you need a $6 – part number 15-75247 bolt. I did not need this bolt, but I did spend the $6 for it – yay.
After doing both jobs within a month of each other I have concluded the Suburban was very easy (with the help of a YouTube video of course). The Envoy is much more difficult.
There is a video on Youtube that is very good - you basically following approach in this video.
https://www.youtube.com/watch?v=7twQRCTv45U
Step 1: Empty the coolant
On the Suburban you can siphon out the coolant since the radiator cap is on the end of the radiator. This lets you put a small siphon hose down the side of the radiator to the bottom. Only a little coolant spills out once that is done. Piece of cake job, no fuss, no muss – only a little coolant spillage when the pump is pulled off.
On the Envoy, the radiator cap is in the middle. No easy way to siphon the coolant. You have to pull the lower radiator hose. It’s messy and you will take a bath in coolant if you are not very careful and patient. The larger the pan you use, the better. I did not see a drain petcock on the Envoy radiator, there may be one – I did not see it.
Tip: there is a small L-shaped metal plate that will block the lower hose from being removed – two 13mm bolts hold this plate to the frame. You will want remove this plate to get that lower hose off.
Step 2: Remove clutch fan
On the Suburban there is a fan removal tool (a long thin metal bar) that can hold onto 2 out of 4 fasteners on the water pump pulley. With the tool in place you can also can get a big 12” adjustable wrench on the fan nut. You hold the fan tool (and pulley) still and break the fan nut loose. With that fan tool, the job is piece of cake – a 2 minute job.
On the Envoy, there are no fasteners on that water pump pulley. So there is no easy way to hold the pulley other than the drive belt – which does not have enough grip.
Tip: put the adjustable wrench on the fan nut, press down hard on the belt. I used the head of a hammer (inverted) to press on the belt. Then you strike your adjustable wrench with a 2nd hammer. Three hands would be ideal. Otherwise, this is tough maneuver and that fan nut is not going to go easy. After about 20 minutes (after you hit yourself with the hammer a few times) the fan nut will break loose – not fun.
Step 3: Remove upper hose. A hose pick tool is very helpful here. Those GM hose clamps are a tough deal. They are actually molded/tethered into the factory hose and cannot be slid up the hose. They do lock open, but they are not fun to deal with. I think there is a tool for this as well – this would probably help.
Tip: you may want to just forget about the factory upper and lower hoses. If your truck has like 100K+ miles and you are doing a water pump, you might as well just cut the hoses as needed to get them off. This is a good time to put in new upper and lower hoses anyway. You don’t want to do this job again for as long as possible. Remember to get new clamps with your replacement hoses.
Step 3: Remove fan shroud and fan together
On the suburban the fan shroud is two pieces. The upper part is held on with 4 bolts and then it can be removed (don’t forget to remove the little transfer case vent hose as well). With the two piece fan shroud, the job is piece of cake – again a 2 minute job.
On the Envoy, the fan shroud is one piece with just two bolts at the top. There are two plastic locating pins molded into the shroud that engage holes in the lower radiator support. The fan shroud and fan have to be lifted out and removed together as a unit. After you remove the two bolts (and an electrical connector) that shroud will not want to come out.
Tip: the fan shroud is also secured with some … flexible polymer sheet material … down low on either side. Each flexible sheet is held on with two small tabs. You need to release these flexible sheets before the shroud will come loose. There is not much room in there, but you can get that stuff released. Once this is done you can work the fan and shroud out. It has to be pushed past the upper radiator hose fitting on the left side but it will come out.
Also, the Envoy has two metal transmission cooler lines that are actually snapped into a double clip that is molded into the lower portion of the fan shroud. Those lines have to be carefully pried out of that molded plastic clip.
Tip: use a heat gun to warm the plastic clip area so the coolant lines can be pried out with minimal force.
OK, at this point you are in good shape – sort of. The remaining steps are pretty simple.
Step 4: Remove serpentine belt/tensioner
The drive belt is easy to remove – just use a wrench on the tensioner. The drive belt tensioner has three bolts that hold it to the pump.
Step 5: Remove lower hose from the water pump.
Tip: just unbolt the water neck and leave the hose and clamp attached. You are buying new hoses and a new water neck. So you will probably be throwing the water neck and lower hose in the garbage anyway.
Step 6: Remove heater hoses from left side of pump.
These also have those GM spring clamps molded to the hoses. You will be re-using these hoses. Luckily they are small and can be worked loose. A hose pick tool is very helpful here.
Step 7: Remove water pump:
There are 6 bolts holding the pump on. They are all the same size. They are not very tight.
Step 8: Re assembly
At this point it’s just a simple matter of cleaning up the gaskets and reversing the process to install. Not a big deal. Follow all the torque values for each set of bolts. The water neck is 11 ft-lbs. Those 6 bolts holding the pump to the block – two passes – 1st pass 11 ft-lbs, 2nd pass 22 ft-lbs. The three bolts holding the tensioner – 37 ft-lbs. Don’t just hammer the things to 400+ ft-lbs with your air tools – no good can come from that.
Step 9: Bleeding - literally
I don’t know what to say about this. I did the job and then started the truck. No heat and the temperature started to climb over 220 … I shut down the truck. In the Suburban, I never had any problems getting the system bled. You leave the cap off and then the coolant flows.
The Envoy never bled itself. It was very clear that coolant was not flowing. There is a vent hose that is attached to one of those heater lines on the left side of the water pump. It connects to a pipe sticking up vertically out of the intake manifold under the throttle body. I removed this hose to “vent” the system – and no go.
I ended up draining the truck and removing the thermostat. I had a spare thermostat so I swapped that in. I refilled the coolant. This time I left the vent hose off – I heard it whistling as I filled the radiator. Started the truck … no heat and the temperature started to climb over 220 – Yay!
So now I know it’s not the thermostat (two in a row can’t be bad). Either the pump was bad (not likely) or the system is still not bled. So I made sure the truck was cool and took it for a short drive. Once it warmed up I mashed the gas pedal … and wait for it … the heat came on. The truck was happy after this. Revving the engine got that coolant flowing. So other than this “procedure” don’t ask me how to bleed this system – mashing the gas pedal is probably not the right way.
So if you want to do a water pump, these are the things you need to know. That video is really good and gets you most of the way there. These tips should save you some time as well.
