How to bleed the coolant system?
Thread Starter
Racer
Joined: Mar 2003
Posts: 309
Likes: 0
From: Las Vegas NV
How to bleed the coolant system?
Just replaced the intake manifold gasket, and I'm getting ready to flush and fill the coolant system. I can't quite tell from the service manual where the bleed valves are. Second question - is there a flush product (Prestone or Zerex) that you'd recommend? The manual says not to flush with a chemical product. I can't tell by looking at the label if they have chemicals. I assume they do.
Drifting
Joined: Mar 2003
Posts: 1,953
Likes: 4
From: either, ca/ohio
Re: How to bleed the coolant system? (mk2001c)
Look in your owners manual. It says in my 87 manual that you fill coolant run car when it cools it pulls water from overflow. It may take several times to get air out.
That was a summary.
:hurray:
That was a summary.
:hurray:
Melting Slicks
Joined: Jan 2000
Posts: 3,418
Likes: 1
From: NW Chicago Suburbs
Re: How to bleed the coolant system? (mk2001c)
...I can't quite tell from the service manual where the bleed valves are....
Eric
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Re: How to bleed the coolant system? (mk2001c)
My 92 service manual says not to use chemical flushes. For a 92 (and probably later LT-1's) flush 3 times with water and pull the knock sensors to drain the water from the bottom of the block. Use distilled water on the last flush. These flush steps include drain, refill, run the engine to a temp of least 150deg each time.
When you have drained everything, pour in 2 gallons of antifreeze (green coolant for pre-95) and then add distilled water. With engine running, bleed the system at both bleedvalves. Make sure coolant is at the top of the filler neck in the expansion tank and replace the cap. Again, for a 92, the engine should run a minimum of 3 cycles where coolant temps go from cold to operating temp and cooldown again before any high-speed operation. Clean out and re-fill overflow tank with a 50-50 mix of distilled water and coolant.
When you have drained everything, pour in 2 gallons of antifreeze (green coolant for pre-95) and then add distilled water. With engine running, bleed the system at both bleedvalves. Make sure coolant is at the top of the filler neck in the expansion tank and replace the cap. Again, for a 92, the engine should run a minimum of 3 cycles where coolant temps go from cold to operating temp and cooldown again before any high-speed operation. Clean out and re-fill overflow tank with a 50-50 mix of distilled water and coolant.
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Verdad Gallardo
Safety Car
Joined: Feb 2002
Posts: 4,212
Likes: 10
From: Sun City West Az
Re: How to bleed the coolant system? (mk2001c)
You might check for a 2nd bleed valve on the drivers side tucked up under the throttle body. Like mentioned before I don't know when they switched from 1 to 2 bleed screws either and mine is a 92 also.
Racer
Joined: Jan 2003
Posts: 360
Likes: 0
From: Sumter South Carolina
Re: How to bleed the coolant system? (ittlfly)
If you're going to bleed the system from the thermostat housing, start up the car and let the system get under pressure. Then open the bleed valve while the cr is running and wait. If there is air in the system, coolant will spit and sputter for a bit, then a steady stream of fluid should come out. When that happens, you're finished.
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Re: How to bleed the coolant system? (Irishpilot03)
I had to loosen the upper radiator hose to purge air trapped in the system while filling the system. Once coolant started coming out of the radiator, I put it back on and used the bleed screw on the thermostat housing then started the engine. I could not get coolant into the radiator until I pulled the upper hose off to let air escape.
I also recommend distilled water instead of tap water. Tap water has a lot of chemicals and clorine that cause problems over time. Its only a $1 a gallon at the grocery store, so not a major expense.
I also recommend distilled water instead of tap water. Tap water has a lot of chemicals and clorine that cause problems over time. Its only a $1 a gallon at the grocery store, so not a major expense.
Melting Slicks
Joined: May 2001
Posts: 2,143
Likes: 7
From: San Diego CA
Re: How to bleed the coolant system? (Mez)
Too get a significant volume of coolant into the radiator, you have to get the engine hot enough to open the thermostat.
If you are going to bleed at the t-stat, be sure to put some rags around to sop up the coolant. Guess what's under the bleed valve!
If you are going to bleed at the t-stat, be sure to put some rags around to sop up the coolant. Guess what's under the bleed valve!
