Coolant flush seems to only flush half the coolant

[asetoftools]

Hello there. I recently decided I had never done a coolant flush, so it was about time to do it. I tested with hydrometer and it was good to only -14*c, so I thought OK i’ll do it. The coolant I took out was all fine looking, green. However there was only half of the coolant I expected. (aprox 4 L, and i expected 8-10L as per the manual).

The haynes manual and dealer manual refer to a vent plug at the “termostat housing” and “Water outlet”, respectively. They say you are to remove it before draining the system. I cannot for the life of me find this thing. I took the whole thermostat off, but more coolant did not drain out the radiator. I refilled with distilled water and prestone coolant flush. I ran the car, and green coolant circulated through the system. I drained again, and its more diluted now but still somewhat green, and I assume also has the cleaner still circulated inside. So now I have been dumping distilled water in there, running and draining, I am waiting till it turns clear. This takes a long time as I need to remove parts of the air cleaner and battery to drain the coolant every time, not to mention waiting for it to cool etc.

question is,
1) how harmful is prestone fuel system cleaner if i cant get it all completely flushed out?
2) Anyone happen to know where the vent plug is on a 1989 corsica’s GM Lb6 2.8L motor? or has a picture of it?
(here is a diagram of the cooling system, but I cant see it:
http://parts.nalleygmc.com/showAssembly.aspx?ukey_assembly=388256&ukey_make=1024&ukey_model=14499&modelYear=1988&ukey_category=19395 )

also the engine diagram and instructions at the bottom of this page, gives instructions listing the vent plug, but not picturing it.
http://www.autozone.com/autozone/repairguides/GM-Cavalier-Sunbird-Skyhawk-Firenza-1982-1994/ENGINE-MECHANICAL/Thermostat/_/P-0900c1528003ba97

is there a better way than one i am doing for a coolant system flush? Don’t really want to run tap water through there at all, but if its the only way…

Topic

[Kevin Criswell]

this pdf shows GM engines in that year range and their vent locations, if you notice on yours the vent is built into the thermostat housing. They do recommend removing the upper bypass hose while filling.

Attachments:

• ventlocations.pdf

[asetoftools]

First off thanks for the PDF. If anyone is interested, it says the following:

MAKE: 1987-89 V6 2.8L
Bleeder type: valve
location: thermostat housing
Fill Point: radiator
Bleed w engine rpm: off
Special Note: With high-mounted by-pass hose (above radiator), also remove hose from pipe

From my looking, the thermostat housing has two bolts in that area. One looks like it holds the engine together on the back, and the other seems to hold a pipe on on the front which cools the throttle body. What exactly Am i looking for? do you have any picture of the kind of valve it is? i have alot of trouble thinking that I am just not seeing it. I felt up the place where the thermostat is mounted on all sides, and those are the only two bolts. Neither of which is particularly accessible.

My upper radiator hose from the thermostat has already been unplugged (there was no coolant in it when i removed it, as it just drains out into the radiator). there is no hose above the radiator at all.

ill take a picture of the area when i get home tonight. maybe someone can point it out to me.

[Kevin Criswell]

[quote=”asetoftools” post=78712]First off thanks for the PDF. If anyone is interested, it says the following:

MAKE: 1987-89 V6 2.8L
Bleeder type: valve
location: thermostat housing
Fill Point: radiator
Bleed w engine rpm: off
Special Note: With high-mounted by-pass hose (above radiator), also remove hose from pipe

From my looking, the thermostat housing has two bolts in that area. One looks like it holds the engine together on the back, and the other seems to hold a pipe on on the front which cools the throttle body. What exactly Am i looking for? do you have any picture of the kind of valve it is? i have alot of trouble thinking that I am just not seeing it. I felt up the place where the thermostat is mounted on all sides, and those are the only two bolts. Neither of which is particularly accessible.

My upper radiator hose from the thermostat has already been unplugged (there was no coolant in it when i removed it, as it just drains out into the radiator). there is no hose above the radiator at all.

ill take a picture of the area when i get home tonight. maybe someone can point it out to me.[/quote]

A picture would be perfect, my memory is not that great anymore and I have not seen a 2.8 in a long time.

[asetoftools]

Unfortunately I cant get a picture of the other bolt under the radiator hose without removing it and draining the system again, which I dont have time to do right now. I believe the bolt that i have hightlighted holds the top of the motor on, and thus is not a vent plug. But maybe you will look and say “well thats a stereotypical vent plug right there!”. Like I said, the only other bolt is the one below holding the throttle body coolant feed.

I guess I could bleed it from the coolant temperature sensor which is at the back? what exactly am I bleeding here? the motor? why does it not flow out? some sort of pressure? I removed the thermostat, how did that not relieve the pressure in the motor?

Attachments:

• overheadshot.jpg
• boltatrearclearview.jpg
• boltatrear.jpg

[Kevin Criswell]

Oh okay, yours does not have the bleeder vent. It would be where the circular indent is on top of the thermostat housing. It might have been replaced at one time in the past. Just loosen the upper radiator hose at the housing and use that to bleed the air out.

[asetoftools]

Sure well that explains why I am not blind, great. But where is the other 4L of coolant and how do I get it out? Is it possible the dealer manual and haynes manual are wrong about the coolant volume, by half?

is the cleaner OK to leave a bit in there if i just drain and refill with antifreeze? or will it slowly eat all my seals/gaskets?

[Jay]

I’m not sure how your doing the draining but why do you need to remove the air cleaner and battery? As far as only getting half of the coolant out. My guess is that your draining the radiator but not the engine or vice versa. You should be draining the radiator from its drain plug and the engine also has drain plug/plugs. Personally I think its a pain to do the engine plugs. What I used to do is remove the thermostat and run a garden hose through the system until it came out clear(just water). Then I would drain out 50% of what was a full fill. For example,If your car holds two gallons, I would drain out a gallon then top it of with a gallon of pure antifreeze. Hope i am making sense,lol. Good luck!

[asetoftools]

Well the drain plug is at a bad location from the bottom, so i have to go in from the top, its just easier to get leverage. I didnt want to use any tool on the plastic drain plug really. And actually I got quite good at it, less than 10 minutes.

Anyways I ran distilled water in to both the radiator and the thermostat housing (through the engine) till it ran clear. With a garden hose, I would make way too much water and I would have had no way to contain it all. Distilled i can just reuse the bottles for waste coolant. Plus no minerals in the engine.

So anyways I did that then I filled it into the engine and radiator with mostly coolant and have been topping it up. Seems to be ok. Its kinda hard to break the car I find, however I want to do things with minimal damage to the car. If I had to do it again, I would use no cleaner, as my fluid was never really that bad (colour, odour, etc), just weak.

I wonder though, when you ran it through the system, was the engine running? If its like a CPU then no cooler = *pop* in short order, so I decided against trying that.

[EricTheCarGuy]

To be honest I’m not an advocate of coolant flushes unless there’s scale buildup or a problem with the cooling system due to some sort of blockage. All that’s normally required is to do an occasional drain and refill, usually about every 30K or so. I’m not saying you did anything wrong, it’s just something I don’t feel is necessary for every application. Not all engines have bleeder valves, in fact, most don’t. The only reason they put those there is to make filling the system easier. If you’re going to bleed the system, I suggest you follow the procedure in this video, minus the bleeder valve part of corse.

Good luck and keep us posted.

[asetoftools]

Well I had to do this again. A rubber heater core hose sprung a leak on the highway.
I parked the car, came back the next day with the hose, replaced it, then drove home with distilled water in it and then drained it out as its about -2*c over night here.

I then did the whole garden hose flush method. I refilled with mostly coolant (about 3L), and bled the system with the radiator cap off. If i opened the throttle, the coolant would overflow so i just sat there idling.

I topped up the radiator whenever the level got lower than the top of the neck. There were many bubbles. I let the car run up till the fan came on (at 80% of temp gauge, as it is supposed to), it sucked more coolant in. The bubbles never stopped, so i figure my coolant was boiling a bit, as even though the bubbles never subsided, the coolant volume stayed level with the radiator neck top.

That’s just a guess, but it seemed logical. So drove it around a bit, seems ok. Temp is rock solid at half where it should be.

I think the reason why previously, i did not think i got all the coolant, was because the yellow prestone coolant seems to turn green when its in the radiator. That or I still didn’t get everything out, even with the pressure of the garden hose and the thermostat removed. heater was on as well.

The only other thing i can think to do is to run the car with the hose in the radiator and the thermostat removed. I was not brave enough to try that today, and nothing i read indicated that that might be necessary for a flush.

we’ll see how it goes

[EricTheCarGuy]

Given that you had a major leak and had to repair it, I think you’ve got all the old out of there at this point. I wouldn’t worry about it from here.

Thanks for keeping us up to date and for using the ETCG forum.

[Author]

Replies