Two Questions relative to 1994 LT1 engine:

1. Recommended procedure for flushing cooling system? On some of my other cars I have purchased a flush kit where I cut one of the heater hoses and insert a plug such that the garden hose hooks up and flushes the system. I assume there is a better or more efficient method for my C4.

2. Replacement antifreeze? I noticed on one thread that there appears to be several options/opinions here and definitely disagreement. Is there an antifreeze product out there that all agree on?

My C4 arrives either tonight or tomorrow......I haven't gotten a good night sleep in a couple of days waiting for the big arrival! My youngest daughter in college has no idea that I am getting this and I plan to pick her up at the airport in it the next time she flies home.....ha ha.....not easy staying one step ahead of teenagers but well worth the effort!

Thanks for responses on the two questions.

K.C.

 

I just ran high pressure water thru the radiator and flushed out all the coolant by running it then emptying it out until it was pure water. Put on two new hoses, thermostat, radiator cap and resovoir. I also did the heater core at the same time. I like Prestone antifreeze. Use 50% antifreeze and 50% Distilled water. Do not use tap water. The chemicals in it will cause premature wear and eat up the rubber internal parts. Put in a new thermostat while your flushing it out along with a new radiator cap, be sure to check the hoses, and keep all your animals away from any antifreeze that may have hit the ground.

You can take a shop vacum and suck out any debris that may have blocked the front of the radiator. It can cause overheating problems. The best way to clean the radiator/shroud is to remove it to use the shop vacum. Our cars are bottom nose breathers so junk accumulates up quite rapidly. Be sure to straighten out any bent fins and burp the system as well.


parts needed:
1. 12-16 gallons of distilled water
2. new thermostat and gasket (recommend AC/Delco, be careful, its special with an extra plate on bottom)
3. Three (3) gallons of old-style (green) pure anti-freeze (not pre-mix) 94's DID NOT use dex-cool -- be careful, its getting hard to find -- prestone IS NOT same chemistry, so try NAPA or local car parts place -- I found mine, brand Texaco at Drivers/FX. do a search for more info on this chemistry issue.

procedure:
0. TURN ON HEAT and raise temp to max (this is so it's not forgotten).
1. drain radiator (pet-**** on passenger side).
2. use a shop vac and a hose to to suck-out and flush/clean coolant in pressure tank (near windshield) and overflow tank (near bumper).
3. close pet-****.
4. Fill the overflow tank with distilled water.
5. SLOWLY fill the pressure tank with distilled water to 1/2 inch below the bottom lip.
6. start car, within 1-2 minutes, add additional distilled water, keeping level 1/2 inch below the bottom lip, then cap off.
7. bring idle speed to 2k rpms for 5 minutes, watching both temp gauges (analog and digital on dash). Both should climb somewhat evenly -- do not allow to overheat, but you want the temp to get to around 200 for at least 5 minutes.
8. turn off engine.
9. allow to cool for about 15 minutes.
10. open radiator pet-**** (do not touch radiator cap).
11. drain radiator -- remember system will have some pressure and will be hot). After 1-2 minutes, open radiator cap (pressure should be relieved so no spewing or leakage).

12. repeat steps 5-11 at least 4 times, but continue until water drained out of radiator is nice and clear (or your down to just 2 gallons of distilled water).

13. The nice thing now is you have nice clean distilled water in the engine block.

14. with system drained, remove thermostat housing and replace theromostat and gasket (with system all flushed, and only distilled water in the block, you can't hurt the opti now, albeit still put rags or paper towels below just in case).

15. close radiator pet-****.
16. use shop vac to suck out anything left in pressure tank and overflow tank.
17. SLOWLY add up to 9 quarts (2 & 1/4 gallons) of pure anti-freeze to pressure tank, keep level at least 1 inch below the bottom lip. Gently squeezing the lower radiator hose can help. If you get all 9 quarts in, then continue with distilled water.
18. open the bleed screws on top of the thermostat housing and then under the throttle-body (driver side), HOWEVER, JUST until some coolant comes out, but be careful -- put rags/paper towels below both to protect the OPTI.
19. Half-fill overflow tank with pure- anti-freeze, and then top off with distilled water (effectively a 50/50 mix).
20. Start car, within 1-2 minutes, continue to add either rest of anti-freeze or or as much as possible, or distilled-water -- keeping level 1 inch below bottom lip. then put on Radiator CAP.
21. run car at 2k rpm for 5 minutes, watching both temp gauges. If all ok, take car for drive, continue to watch temp.

22. allow car to cool for 2-3 hours, open radiator cap and top off -- again keep 1/2 inch below, also check the overflow tank and keep it at full-hot level for next 2 days or so.

23. Do not drive car hard for 2-3 days to allow coolant to mix throughout the engine.

 

I tried the Prestone super flush, it did OK. After flushing a few times I got around to opening the block drains. Lots of junk down there that flushing didn't help.

 

Thanks for the detailed report. I will print out and file with the rest of the articles that I am reading. We have well water which is full of minerals, etc. that are really hard on internal engine parts....so I need to buy a couple of gallons of distilled water and keep in the garage.

 

Not a problem. Goodluck.

 

12-16 gallons of distilled? Ouch! Just use the prestone super flush and drive around like the instructions tell you to. It cleans pretty well. If you really would like it clean the block drains have to come out, a lot gets stuck there.

With the flush you just drain it, add the flush and water then drive normally. I've got a water filter here and use filtered water instead of distilled. I tried the hose connection flush method and it isn't really needed. Just put the hose in the radiator and drain it.

For coolant I like to use the stuff that breaks down in the sewer, it's easy to get rid of unlike some of the others.

 

I did not make those instructions. I merely copied and pasted them from another thread so to whoever made those instructions, I take no credit for them. Nice write up though.

 

The FSM does not recommend the use of flush agents, only clean water. It does recommend the use of distilled water for the final fill.

To do a complete flush as described in the FSM, you have to remove all of the coolant in the block along with what is in the radiator. Drain the radiator at the petcock and then remove the two knock sensors at the bottom of each side of the block. There are small covers that have to be removed first.

Once you have that done, replace the knock sensors, close the readiator petcock. and open the bleed valve on the thermostat housing. Fill the system until wter comes out of the bleed valve and then close the valve. Continue to add water until the level is at the bottom of the filler cap neck.

Start the engine and let it idle watching the coolant temp. When the t-stat opens, you should see the water level drop quickly. Add some more water and let the motor run for a couple minutes but watch to make sure that temps dont' get real high.

Drain as before, refill and repeat.

After that, drain the water again. Use some anti-sieze compound on the threads of the knock sensors and re-install them with the shields. With the radiator petcock closed, open he bleed valve and add two gallons of green (ethlyene glycol) coolant concentrate (you can use a pre-mix, but the cost of the concentrate and distilled water is much cheaper). If the coolant comes out the bleed valve, close it. If not, begin to add distilled water until coolant comes out the bleed valve then close it.

Continue to add distilled water through the filler neck until it reaches the top. Start the motor and let it idle until the t-stat opens. Keep adding water until the coolant level is at the base of the filler neck. You should get the two gallons of concentrate and two gallons of distilled water into the system. After that, mix them in a 50-50 ratio and top off as needed. A 50-50 mix provides protection to about -37 degrees F.

Keep an eye on coolant temps while you are doing this! If the temps go above 220, shut the motor off and let it cool. then start again. Replace the radiator cap and watch the temps.

Also per the FSM, do not do any WOT operation until after the motor has gone thru 3 complete temperature cycles where the coolant goes from cold to operating temp then a cool-down to <100 degrees F.

While you are doing the flushing, you can remove the plastic overflow tank and clean it out. Don't add anything in there until you have finished the flush and installed the new coolant. When the motor has cooled off, add a 50-50 mix of coolant and distilled water to the "Cold" line.

If your radiator hoses are original, this is a good time to replace them,especially the lower one. They do get soft after the years and a collapsed hose will quickly cause overheating. Same with the radiator cap; get a new one as they don't cost a lot of money.

 

Thanks for the compliment -- I wrote-up those instructions for a different post based on our 1994 LT1.

The one improvement I've discussed with other members since, was to also use the shop-vac in blower-mode to push additional coolant/debris out of the engine, after each draining -- blow air into the black pressure tank where the radiator cap goes, it will help remove additional debris that might remain in the engine near the 'knock-sensors', eliminating the need to remove them to completely drain the block.

Regarding the cost/quantity of distilled water, I also have well water so can't use, but considering the 12-16 gallons of distilled-water only cost $12-$16, it's well worth it to assure nice clean water in the block.

 

Is that AC/Delco thermostat gasket reusable?

I have an 89. I plan on flushing it with water as I've got gunk build up. Would it be good to remove the thermostat while I'm running the engine with water in it? I figured that would save time on the drain/refill/drain/refill as you have to wait for the thermostat to open.

I plan on using a flush by Kool-it.

And where are the drain plugs on an 89 with L98 engine?

 

I have never wasted my time with distilled water. straight from the garden hose,

 

I am considering doing the same thing. I have a thermostat that is stuck closed on mine. So I was thinking remove it, reinstall the neck and hose. Flush the system a few times, then install the new thermostat. Any potential problem doing this?

Also does anyone by chance have a photo of illustration of the second bleed valve on the lt1's by the throttle body? I can not for the life of me find it.

 

LT1Corvette,
Later LT1's have only one bleed valve even though the 'books' say that there are two. Don't feel bad, I looked for 2 weeks before getting 'clued in.'

 

Forget about filling the radiator and flushing it 4 times with distilled water. Who's got time for that and what a waste of 14-16 gallons. Just open the block plugs or knock sensors as others have mentioned, drain the radiator, button things up, fill with water and run until the motor is at operating temp, remove plugs and drain the block and radiator again and fill with approx 1 gallon of antifreeze and 1 gallon of distilled water. The cooling system will be a lot cleaner that 4 partial flushes.

 

Thank you for putting that to rest. I spent several house this weekend looking for it and scratching my head like a bloody monkey. Got so frustrated today I stopped in at the dealer to see if the part showed up on their computer program. Even after it didn't, I still was not satisfied.

 

Where are the drain plugs on an L98? And can those be removed without having to lift the car or use ramps?

And when flushing, instead of running it till it gets to operating temp, could you just remove the thermostat and run it? Or is there another purpose of letting it get to operating temp with regards to a flush?

 

The second air bleed screw is on the throttle body.

 

If you have aluminum attached to iron in the presence of an electrolyte, then you get a galvanic effect. Heads are Al, block is iron, in electrical contact with one another via the head bolts among other things. If you want a battery to form, just add electrolyte, which is garden hose water.

Same idea as to why they put magnesium anodes in water heaters, so the Mg dissolves before the rest of the tank - its a sacrificial anode. If you use hose water, then your cylinder heads and other aluminum parts become the sacrificial anode. Other than human error in installation, galvanic corrosion is the # 1 cause of head gasket failure.

 

And don't over-tighten those brass bleed valve screws or use the wrong-sized screwdriver to loosen them, either. Brass is a soft metal and it's easy to damage the screw heads.

 

I have 2 GM bleeder screw assemblies for sale... should anyone ruin theirs.