Hey all! Im doing some way over due services on the 87 I recently picked up. Tonights task is a coolant flush. Im a little uncertain on a couple things and would really appreciate a little advice. I have 1 gallon of concentrated GM dexcool. The label says its backword compatible with pre 95 cars. But, is there something you guys have used that these lovely engines prefer? Also, is 1gallon enough to do this job? And lastly, how do I bleed the system once its full? I thank you in advance for any advice!

 

Dexcool should be fine to put in, I would just watch what comes out pretty closely to make sure you don’t mix and match what was in there. If you see green, fill and flush again with distilled water.

Coolant capacity for these is around 14 quarts (3.5 gal) so you’ll actually want a little more concentrate unless you’re shooting for a different ratio than 1:1 water to coolant.

To get as much old coolant out as possible, you’ll want to pull the knock sensor on the passenger side of the block as well as the coolant line going to the oil filter mount on the driver’s side.

To bleed the system without a kit hooked to the radiator, I’ve just been pulling a small hose off the line to the heater core. It’s pretty high up in the system so it seems to clear air pretty well. I can send a pic if you’re not sure what I’m talking about.

 

*1 Gallon is not enough. You'll need about 3 gallons
*Buy the premix aka "50/50" to eliminate any issues from tap water.
*By "Flush", I hope that you mean completely drain (block drains and heater core, too!), flush, then fill from empty? This because....
*You do not want to mix Dexcool w/what was in there previously, unless you know for absolute certainty, that it was also, Dexcool.

People will try to tell you otherwise, but Dexcool is a good product and will work fantastic. I've been using it in fleets that I've managed maintenance on, for nearly 25 years. Probably over 1000 vehicles from snowmobiles to dump trucks, and it WORKS. I've posted pics on here of three of my personal vehicles that had gone past 150k miles on Dexcool and had radiator failure (two cracked side tanks and a cow-strike). I pulled the side tanks and took pics of the insides of the core and they looked brand new inside. If you don't like changing coolant every 1-2 years....if you don't like changing heater cores....use it and it works.

 

this one here should get most of the air out if you disconnect it while filling.

 

Thank you guys! That was just about everything I needed to know. So the hose that sredwine posted a pic of....Ill disconnect that. And once its full, do I leave that line disconnected while its running and up to operating temp for a few? This is my first time in case you havnt figured me out yet (blush)

 

I connect it again once I’ve topped out the radiator and then run the car with the heater on to flush bubbles back to the radiator. Once it’s cooled down again, check and refill the radiator and I’m usually good to go. Not the recommended way necessarily but it’s worked alright for me.

 

Thank you very much!

 

Springboarding off of the existing thread because it is the same version as my 88.... and whether I have done things terribly dumb or possibly good it might help someone in the future.

I have parked the car with the right front end slightly down hill, removed the thermostat, lower radiator hose and the return line to the heater core.
Then I flushed the system forward and backwards for several minutes with a city water hose.

Now that I have all of the coolant out the low spots of the engine have regular water in them. To those of you who know the engine design, if I use a vacuum to pull the water from the low spot in the lower rad hose, will that get 99% of the water from the engine?

I have 2 gallons of coolant and 2 gallons of distilled water that I want to mix and get back in there but I don't know how to flush the system and not have the hose water in there. I read the parts about pulling the knock sensors but I have pull the car into the grass to get the front end lower and there's no way for me to jack the car up to get under it now. Also, those aren't broken yet and didn't want to pull them out and cause myself a new problem.

 

I don't think you'll get the water out of the block. You need to pull the block drains.

 

My 96 coolant layout is somewhat different than yours but you might get some ideas with my old post. Dan

Shop vac flush works! - CorvetteForum - Chevrolet Corvette Forum Discussion

 

Man.. that really blows.. 😎
i think i can source a vac that also blows... i might give this a try.

 

I think almost all shop vacs can blow. Just move the hose from the suck tube to the blow tube. Dan