2015ChevyExpress2500

Hey there guys. I just bought a used commercially owned 2015 Chevy Express 2500 4.8 V8 w/ 104,000 miles. It runs really strong, has a very clean body, so far so good(fingers crossed). The Carfax states it was taken to Stevens Creek Chevrolet in San Jose, Ca for service. I went to the dealership for intel. In fact 5 months ago the engine seized and the previous owner had the entire engine replaced for a little under $8,000. So it basically has a new(probably used) engine. The only problems I noticed was a very light buzzing noise coming from the 12 volt plug on the dashboard in the start of acceleration...

My first plan of attack was to change the oil. Last weekend, I put Mobil 1 Advanced Full Synthetic and a nice Mobil 1 filter. My goal this weekend is to change(but not flush) the vans coolant. I have the new updated 1996-2019 Haynes Repair Manual and of course the directions are very general. I haven't checked if there's a drain valve on the left side of my radiator yet. Any advice/instructions would be greatly appreciated. Also, is it okay to use pre-mixed auto store DEX-COOL? I'm just doing this fluid change for good measure, after this I will change the transmission oil/filter... Thank you very much, any advice is greatly appreciated!

tech2

should have a drain plug...spray it with penetrating fluid before trying to turn it out. if the lower rad hose is easy to access... leave the drain plug and remove the hose...it will get more coolant out than the drain plug. As long as the old coolant is at 50% or higher concentration...using premix is fine. if you do go with a concentrated version...mix with distilled water as hard water will reduce the effectiveness of the corrosion inhibitors. keep the concentration between 50 and 70%.

ideally the best way to fill is will a vacuum filler....pouring it in manually will require thermocycling to get all the air out.

mountainmanjoe

I didn't bother with drain plugs. I pulled the bottom rad hose off the water pump and stuck it in a bucket/pan. It drains the rad and it's less messy.

Coolant is cheaper in concentrate.

This is how I did my coolant replacement:
https://chevroletforum.com/forum/exp...e4/#post430529

2015ChevyExpress2500

Thanks for the information. I'm an amateur at diy maintenance. I think so far I'll be good at emptying the coolant from the lower radiator hose, and then the cylinder bock drain plugs right? That sounds easy... What I don't understand now is do need to remove the thermostat( I don't think I do if I didn't flush right?)?

Also I don't have vacuum filler, and don't know what thermocycling is... The Haynes Manual says to (for 2003 models and up)
-place heater controls in maximum position
-Disconnect upper radiator hose and the bleeder hose from the radiator, then using a funnel slowly fill upper radiator hose until a steady bubble free stream of coolant flows from the bleeder hose.
-Reconnect the upper radiator hose and bleeder hose to the radiator
-Add more coolant to the radiator through the filler neck, then add coolant to the reservoir
-Run engine until normal operating temp is reached then allow to cool
-check levels

If someone could give me their own step by step directions, that might help me/give me more confidence. I know I'm asking for a lot here... Any advice is greatly appreciated, thank you so much.

mountainmanjoe

I didn’t bother with the thermostat to drain the engine block. The plugs are too difficult to get to. Unless your coolant is really sludgy I wouldn’t worry about it. As I wrote in my post, I used a garden hose to push fresh water into the block through the heater port. Good enough.

thermocycling just means getting the engine up to operating temperature so that the thermostat opens. I don’t think yours has a heater valve so it doesn’t matter if you turn it on or not.

2015ChevyExpress2500

mountainmanjoe, I will use your method. Just a couple of questions before I do this on the weekend...

1. Can I keep my van on the ground, I don't have a big enough jack? I kinda fit under though...

2. Will the coolant still drain properly with the thermostat in place?

3. Do I have to do anything special with the reservoir tank hoses, or do I just remove and move the hoses aside?

4. First you flushed the heater core/engine block by attaching a garden hose in one end of the heater inlets and flushed it out the other until clear...

5.You then used a cheap flush kit because I guess you wanted to flush it even more, could I just stop here, or do I need to even use a flush kit????

6.Correct me if I'm wrong on the wiring of everything for using a flush kit if needed... The coolant will be coming right out of the radiator return inlet(right in front of the thermostat/water pump) which is connected by the lower radiator hose to the radiator. You leave this open during the process. You then leave the "return from heater hose" in/connected. Now this is where I'm very confused. The fifth picture with the connections for the flush kit confused me. The top of the T is obviously the garden hose.

-Is the hose on the left of the T connection the "out to heater" hose????
-Is the hose on the right of the T connection going back the the "out to heater" inlet????? Why is there a hose connected to the "out to heater inlet" is that going to the T?????

I want to do a proper job, because I understand how important my cooling system is, any advice is appreciated, thanks!!

tech2

if you backflush with h20. to get the proper final concentration; when you fill...use concentrated coolant 1/2 the volume of total system capacity...top off with distilled water.

mountainmanjoe

I didn’t lift the van because I didn’t need to get under it. I just slid a big deep pan underneath.
I was able to reach everything I needed from above.


The radiator drained out through the bottom hose. The siphon effect might have pulled something out of the motor, but as I said I used a garden hose to push the rest out. The thermostat only blocks the rad return.

I removed the reservoir for cleaning and because it’s in the way. It takes 2 seconds to yank off the hoses.

you can flush the heater with just the garden hose but you need the adapter to flush the engine block.

coolant goes through the engine and out the top hose to the rad, then down and out the bottom.

it doesn’t matter where you T in.

2015ChevyExpress2500

Okay thanks for your help guys. I flushed and filled the van yesterday. Man, those hoses don't come off easy, it tool me a while to get the lower hose off. Luckily I had an old pair of Robogrip pliers for the big crimp clamp.

Also, there wasn't nearly enough coolant in the van, and the coolant that drained out looked really weak.

I found Prestone concentrated Dexcool coolant on sale, so I picked up 2 jugs.
After flushing with my hose w/ the flush kit, I filled the radiator w/ 2 gallons of distilled and brought the van to temperature, then drained it.

I filled properly through the upper radiator hose(w/ the bleeder out), and was only able to put in about 10-11 quarts(the vans capacity is 12.4quarts), my theory about this is that I wasn't able to fully drain out 100% of the water leaving maybe 1 or 1 1/2 quarts of water.

My only worry is that the current coolant in the van is somewhat weakened or possibly there is a little hose/distilled water in the system. I'm not to worried though because I mixed the Prestone perfectly, it's a good quality coolant, and I guess the coolant should have stuff in it to prevent corrosion. The current situation is way better than what was in the vans system before. Thanks for the help!