I want to change the coolant in my C5. Is there a radiator drain plug & if so, where is it & what does it look like? I see a white, teflon piece that looks like it may be what I'm looking for but I'm not sure. It's located at the bottom, under the lower radiator hose. Looks like you need a square bit to remove it but a wide bladed screwdriver will reinstall it.

If that's not it, will I have to remove the lower radiator hose?

Is there something I'm overlooking? Is there an easier way?

 

Use a 1/4" square drive and turn only 1/4 turn CCW to drain and 1/4 turn CW to tighten. Here's the drain/refill procedure.

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Draining and Filling Cooling System

Caution
With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result.

Important
If the procedure below is not followed a low or high coolant level condition and/or vehicle damage could result.

1) Park the vehicle on a level surface.
2) Remove the surge tank cap:
3)Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
4) Place a drain pan under the draincock.
5) Open the radiator draincock.
6) Allow the cooling system to drain completely.
7) Inspect the engine coolant for the following:
Discolored -- follow the flush procedure below.
Normal in appearance -- continue with the next step.

Notice
When adding coolant, use DEX-COOL® coolant. If silicated coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner-at 50 000 km (30,000 mi) or 24 months.

Notice
Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

8) Close the radiator draincock. Tighten.
Tighten the radiator draincock to 2 N·m (18 lb in).

9) Fill the cooling system through the surge tank.
10) Fill the cooling system with a 50/50 mixture of DEX-COOL® coolant and deionized water.
11) Start the engine.
12) Allow the engine to idle for 1 minute.
13) Install surge tank cap.
14) Cycle the engine RPMs from idle to 3000 in 30 second intervals until the coolant temperature reaches 99°C (210°F).
15)Shut off the engine.
16) Remove the surge tank cap.
17) Start the engine.
18) Allow the engine to Idle for 1 minute. Fill the surge tank to 12.7 mm (0.5 in) above the COLD FULL mark on the surge tank.
19) Install the surge tank cap.
20) Cycle the engine RPMs from idle to 3000 in 30 second intervals until the coolant reaches 99°C (210°F).
21) Shut off the engine.
22) Remove the surge tank cap.
23) Top off the coolant as necessary, 12.7 mm (0.5 in) above FULL COLD mark on the surge tank.
24) Rinse away any excess coolant from the engine and the engine compartment.
25) Inspect the concentration of the engine coolant.
26) Install the surge tank cap.

 

Thanks again.

 

The drain plug can pull out after turning 1/4 turn. Do NOT turn more or you will break it (don't ask), you can get a replacement at NAPA for $5. You probably need to jack up the car to get at the drain plug, but lower it to level to drain. I drained out to within a quart or so.

Use distilled water to mix with dexicool.

 

Great Info Just curious where you got this info? Experience or the manual or even better both

 

Both. Done several head/cam/header and s/c installs which require draining the coolant.

 

Thanks for sharing your expertise on the site Your a good man Charlie Brown

 

I turn the drain plug 1/4 turn to loosen. It backs out just slightly but no coolant comes out of the drain pipe. I tighten it back by turning 1/4 turn & it seems to go into a detent position.

I'm puzzled as to how to get the coolant to come out of the radiator. Do I need to pull the drain plug all the way out after loosening it 1/4 turn? If it is broken, how can I tell? I bought this vehicle used.

 

Billy is the surge tank cap off . I think it might not drain if that is on.

 

I've tried it with the surge tank cap off. I've also allowed it to come up to normal temp in hopes the pressure would build up & allow the coolant to come out.

All I can think of now is that the drain or bottom of the radiator is clogged up with sludge or something OR the drain plug is not operating properly.

I'm going to take it for a spin to allow it to build up max pressure then come back & see if the coolant will come out.

Any more hints/suggestioins?

 

Drove the car a few miles to build up pressure. Coolant still won't come out. Went by a shop located nearby who specializes in Vettes. He says not to use Dexcool. Showed me a jar of used Dexcool with a lot of sludge in the bottom. ?????

Have hear many horror tales regarding Dexcool.

Anyway, I'll be happy just to get the old coolant out....

 

You may have the sludge problem but you should be able to see signs of it in the surge tank. Let the coolant cool down to room temp, try and remove the draincock and see if you can get the coolant to flow out. If not use a small screww driver to carefully probe the drain hole to see if there's a sludge buildup. If so, you're probably in for a full coolant system cleanout at the dealer.

 

OK, here's what I "think" the problem is. It appears the teflon drain plug piece is just a part that engages the actual drain plug via two "****" that drop into holes on the outer edge of the drain plug. My problem appears to be that the "****" are rounded off & don't engage the holes good enough to loosen the drain plug. Therefore, I can't get the drain plug to open. I guess also that it's froze up as it's probably origional & has been in place for about six years.

I guess I'll just have to purchase a new teflon piece in order to see what I'm dealing with.

I fooled around with it a bit more & ended up prying out the teflon piece. The coolant immediately started flowing out. The teflon piece has an o-ring at the end but I don't see what keeps it in place. Do I need to install a new teflon piece so that I don't loose my coolant?

 

Look closely, the Teflon piece should have one or two small prongs coming out of it, you probably broke them off. Like I said, a new one is under $5 at NAPA.

 

This has been the coolant change from hell....

The coolant came out just fine after I pried the petcock out. Upon examining it I discovered it is broken. The pin the sticks out one side was broken off. Because of this, when I loosened the petcock, it would not back out enough to allow the coolant to come out.

I'll get a new petcock today & hopefully get the job completed. It's really not that complicated as long as the petcock isn't broken.

Another issue is some folks say use Dexcool, others say flush it out completely & put the green stuff in it. Opinions?

The coolant in my car is probably origional (I'm not sure as I purchased the car used). It's a '99 & has 42,000 miles on it. The coolant looks fine. It's not milky looking & I don't see any sludge.

GM says to use Dexcool & I've read lots of stuff about it. It seems as long as it's mixed 50/50 & it's kept nearly full, there's no problem. The problems seem to crop up is the system gets low & a lot of air gets in or it's diluted too much with water. Other opinions?

Thanks in advance for the many helpful tidbits shared on these forums.

 

Aluminum block = DEXCOOL.

The regular ethryline glycol (green stuff) will cause unceccesary corrosion. It will also form a gel over time when mixed with DEXCOOL. Stick with what GM recommends. They put DEXCOOL in for a reason.....

 

Use dexicool. It will not sludge up unless you have an airleak, and then you have other problems.

I changed my coolant out after 50,000+ miles and 5 years, it was clean. The Shop Manual says if it is clean you do NOT have to flush it. I did NOT flush it.

Do mix dexicool with distilled water (Wall Mart or grocery store).

 

Thanks for the opinions. I've had good luck with Dex-cool thus far. Will put Dex-cool back in.

 

Regarding DEX-COOL.

GM is currently under a lot of Legal Fire for DEX-COOL related problems. There are at lease 8 class action suits files, look at the info on cwcd.com/pdf/dexcool_complaint.pdf.

I did a Google search for DEX-COOL and found quite a bit that's disturbing.

Bob

 

DexCool may have some problems, but I think most problems people have is due to lack of cooling system maintenance. I have drained Dexcool out of multiple GM cars (Corvette, Camaros, Impala, Malibus) I have owned since 1996 and have never seen any sludge or corrosion problems. However, I usually do not let mine go over 2 to 3 years without changing the coolant even though it is supposed to last 5 years.

A lot of the complaints seem to be intake manifold leaks, which may be just a poor gasket or intake design, and may not be the fault of the coolant. I have had intake and throttle body coolant leaks on other GM cars that still used the green coolant.