Hi guys,

I am planning on changing out the coolant this weekend at the same time I change the thermostat to a 180 degree one. Also, I don't know what's in the system, so I am setting it back to CoolDex.

1) Am I correct in assuming that the radiator doesn't have a cap, and that the expansion tank is pressurized?

2) If I back-flush the system (using the Prestone's old 'flush and fill' kit), which heater line should I "Tee" into - the one going to the thermostat housing, or the one going to the bottom of the radiator?

3) I am also considering that it might be easier to use a pump to force a 50-50 CoolDex mixture into the system via the heater-hose "Tee" than to fill the system another way.

4) How do you fill this thing up if you don't have a radiator cap? Do you fill through the thermostat opening?

Any advice would be greatly appreciated.

Sincerely,

Rob :)

You fill it through the remote tank on the firewall. It looks like an overflow jug but if you will notice it has a pressure cap on it. On mine there was an 3/4 hose connecting it to the radiator. You may have to pour it in kinda slow due to this. Also don't forget to open the bleeder valve on the thermostat housin when you start. I kept pouring until I got a steady stream out of that valve, then closed the valve off.

Hi guys,

Here's a picture of the two heater hoses going into the passenger compartment through the firewall. Can you tell me which one is the heater inlet?

The metal one that turns into green hose is the input to the heater core.

When I cleaned my system I removed the thermostat and put the housing back on.

Disconnected the upper radiator hose from the radiator.

Put my garden hose in the radiator.

Ran the engine. While the hose was feeding the radiator the engine pumped out everything through the upper radiator hose.

When the water comming out was as clean as the water going in, I put the t.stat back in, reconnected the upper radiator hose, drained out the water and put my 50/50 dexcool/ deionized water in.

This was a messy, but fun way to clean my system.

I even called the water company and they told me that anti-freeze was good for their treatment facility, so it was OK to let it go down the drain, just don't let a puddle accumulate that an animal could drink from.

I think that green/metal hose is the A/C hose, not the coolant hose.

As far as that old coolant . . . here kitty, kitty, kitty. :)

The cap on the plastic tank on your firewall is your radiator cap and the point where you put your coolant in.

I think that green/metal hose is the A/C hose, not the coolant hose.

As far as that old coolant . . . here kitty, kitty, kitty. :)

That green metal hose shown there is a heater core hose, in or out I'm not sure but for sure a heater hose. Thats the one that got a hole in it wen I did my cooling system mod.
Good luck and up date us

Thanks MDT,

That's a great idea!

By the way, I've been searching fruitlessly for the draincocks for the radiator and the block. Would you guys enlighten me as to where they are? Photos would be priceless. I tell ya, the Helm manuals are for the birds on a lot of things. They try and cover so much that they end up not telling you a lot. They just say "open the draincocks all the way, and put the coolant into the radiator after you take off the cap." :rant:


Hmpf. The factory manual on my Toyota is a whole lot better. It has diagrams and exploded views for just about everything.

Sincerely,

Rob :)

. . . . .
By the way, I've been searching fruitlessly for the draincocks for the radiator and the block. Would you guys enlighten me as to where they are? . . . . .


Can't speak to a block draincock, but the radiator draincock is on the drivers side bottom. If you peer down right alongside the tank you'll see a white plastic valve - that's it.

FWIW, I don't use the radiator draincock - period. Too many times in the past I've used it on GM products and it's been nothing but trouble. They either break or don't seal back up. Your mileage may vary. I drain the system via the lower radiator hose.

Oakie Dokie. I finally got around to doing this the other day. Boy what a mess! First off, it appears that one of the studs that holds the thermostat cover on was seriously cross threaded. I was barely able to get it out with the 1/2" ratchet and a good socket. It was clear that the last person to mess with this had cross threaded it, and just forced it into the aluminum to make it work. What a mess.

Something that started as a 45 minute maintenance turned into an all-afternoon ordeal. I needed to buy a tap and die that fit, needed to buy a new threaded stud (by the way, the one that holds the fuel drain valve is a really weird stud. It has a nut welded on the middle section! Unlike a normal threaded stud, which simply has threads on both ends and a blank spot in the middle (for you to grip while turning it), the GM item has threads on both ends and a flange nut in the middle!

MDT's method of disconnecting the upper radiator hose and letting the water pump pump all the old coolant out is simply brilliant. I have actually had problems (as many have warned) of having the plastic drain valve fail on you. It makes a huge mess, because you need to pull the radiator and then take it to a repair place to have it desoldered and fixed. Ack! Anyway, the old coolant (which appeared to be regular Prestone green) all pumped out nicely. I continued to idle the system (with the thermostat out), until the water was clear and clean.


After the trying time with retapping the aluminum crossover, I was able to install the new stud, and then put everything back together. I filled the system by disconnecting the lower radiator hose, letting all the water drain out, and then pouring new coolant into the top of the radiator. I know the system holds 6 gallons, so I knew that if I could get 3 gallons in, I would be at 50/50.

The 180 degree thermostat was really different from the old one. The old one was extremely constricted. (I'll take a photo and post it for you guys to stare at). The new one clearly has a lot more flow - it is of a much more open design.

Anyway, after buttoning her up, and bleeding some air out, I took her for a spin late at night. The temps were down considerably. I can see that instead of averaging 200-210 degrees, it is now around 190. Over the next week, I continue to add coolant, and burp the system of air with the bleeder. The temperatures here soared to around 100-102 degrees, and I took the Tahoe out and drove it up a steep hill. It topped out at 215, but quickly settled back to 190 as soon as the hill was over.

It's running a LOT cooler, and I have a little more flow and safety margin now.

Thanks for all the tips and tricks! You guys are great!

Sincerely,

Rob :)

Turn on the cabin heater to get it filled with coolant.

TurboTahoe,
Not sure if you owned this since new, but my 95 Yukon was equipped with green coolant and I switched over to Dexcool at about 50,000 miles. That was an improvement, but my method of flushing was a bit different. I used all distilled water in the flushing process because I've seen one too many cooling systems contaminated by horrible tap water. Do a search on www.webshots.com for 6.5 diesel and you'll see my water pump / timing gear photos (name there is damork). You may not be able to see it real clear, but the cooling passages are very clean. When I first switched to Dexcool I was running 195F thermostats and saw temps like you see. I then switched to a Robershaw 180, and it would hold at 180 except when real hot and climbing hills. When I went to the HO water pump and dual thermostats (dual Robertshaws), it hugs 180F most of the time, I don't think it has ever went beyond 195 under any conditions since.

With respect to your coolant line that is green and connect to the crossover manifold - if you still have the quick connector you might consider replacing it with a pipe nipple as the quick connectors leak. I bought a nipple from GM for a old 6.2 which has the orifice in it to regulate the right flow through the heater core - price was under $5. I don't have the part number now, but I owned an 83 Jimmy with a 6.2 and it had one. The only other thing you need is some 5/8" hose, clamps, then cut off the aluminum pipe and slip the hose in place.