Coolant Flush

I'm not the authority by any means, but I draw my answers from my limited personal experience.

You could siphon the reservoir, or you can take it off and drain it. On the earlier cars, it was a bolt on the top and it pulled out of the top. I'm not sure about the '94-95 cars.

Don't know about this, sorry.

There is a block drain on the side of the block somewhere, but I've never used it. May be one in each side. I'm not sure how often it's necessary to drain the block... maybe a good couple of flush-fill with water cycles would work.

My experience has been (and prepare to make some mess - I never can do this right)...

Open the radiator cap and fill to near the top. Start the engine and allow it to warm up. When the thermostat opens, you will begin to fill the rest of the system (upper radiator hose and top of the radiator). The level will probably fluctuate here. Add until completely full to the top, and maybe then some. Allow some running time for the system to burp, then put the cap back on before the coolant gets too hot. I recommend a funnel designed specifically for radiator use.

The theory here is that the coolant system should be as air-free as possible. Steam pockets are your worst nightmare and can cause spot overheating, extra cap pressures, etc. It is a closed system and works with the overflow. The overflow *will not work* unless the system is free of air. Pressure will not force extra coolant to the reservoir, just cause a pressurized pocket somewhere, and the lack of pressure will also not cause a draw if there is air in the system. You can not fill via the reservoir.

I don't know if this exists on the '94-95 cars. I don't think there is one on the pre-'94 cars. Basically, in lieu of what I wrote above, we realize that in a normal state, air will rise to the top of the system. The vent plug would be the highest point of the cooling system, and would allow you to vent the air and even top off the system. This isn't really something you can readily add to the best of my knowledge.

Make sure your mix will protect the car down to the coldest night you might have. If not, the mix could freeze, causing anything from a cracked freeze plug to a broken block and anywhere in between. I'd keep the 50/50 mix.

Sure.... if it helped.

Sounds like it should run pretty well... good luck!

JS

The cooling system cannot "suck" coolant from the overflow reservoir until the system cools..... I think they taught that in about grade nine (being a grade 8 dropout, I can't be sure). Snide remarks aside, the job isn't finished until you see evidence that the thermostat has opened and coolant is flowing through the rad. I'm forever amused by the 20 minute thermostat changes.... professionally, I have to be sure that your cooling system is purged and I need to get paid for that, too.... a.8 to 1.1 hour charge for a thermostat change will include the purge process.

Flushing chemicals are caustic.... the act of using them can damge the cooling system. If the cooling system has been neglected to the point of calcification, 'rodding' the rad core is probably a better choice that chemicals that will add insult to injury. The idea is to replace the coolant before Ph or electrolysis has the chance to do damage.

Location of the block drains varies from motor to motor.... they are simply pipe plugs inserted into the lower portion of the block .... below the expansion plug line. If the plug wont come out, leave it alone unless you are going to pull the motor anyway.

The 5.0 has no purge fittings.... other motors might. The 5.0 would have benefitted from purge fittings.

There is no magic involved in auto repair... everything is a logical progression of cause and effect - though there are those things that can tax logical thought process. For the small amount of coolant in the reservoir, I wouldn't get too concerned over it's effect on the outcome of my service routine.

Heat transfer differs between straight water and mixed coolant...... glycol absorbs heat more slowly than water. The car was designed so that the ECT was calibrated for the absorbtion rate of a 50/50 mix. Where I live, 60/40 or even 70/30 can be a wiser choice (with high glycol concentrations, gelling can be a concern). Additionally, good quality coolants offer anti-corrosion additives that will slow down the degradation that will happen no matter what we do.

There is so much more to coolant than being "nice and green".....

Thanks,Jim!

I was loathe to comment since I've used up my "smart-ass capital" for the month. and that's "Hard Work"

But to summarize all this:

• Glycol doesnt carry heat as well as water, that's how the specific gravity coolant testers work.

• "Flush" chemicals can cause more damage than good.

- use clean water, several times, at running temp

• Purging air is more important than "flushing"

• air collects up, so a "flush (Tee) connector" instead in the heater line a foot or so from the intake end might help a lot

Some added thoughts... lots of folks used distilled water in the mix, no chlorine, no lime or iron -and cheap-

Also there IS one of those additives that really works..

Red Line Water Wetter which breaks down surface tension and provides better cooling properties... IT MAY do more than that... After I tore my SVO engine down, removed water pump and the cylinder castings were gray NO RUST, little sediment of any kind.. as if it had just been built

... and I am never precise about coolant condition, or any other scheduled maint.

Jim Warman opined in news:3PDkd.79806$E93.69571@clgrps12:

I've never given the purging of air much thought. I have always assumed that the air would be bleed off into the coolant overflow reservoir ( or in the old days to the ground) as the water temp and pressure rose. Isn't the top of the radiator the "high" point in the system? I'm going to guess that you are suggesting that there may be areas within the system that might allow an air pocket to be "trapped" but if this is the case then it's not obvious to me how it can be purged. After all the system is under pressure when it's at operating temperature so what is it that allows one to purge the system when cold that's different when it's hot? The water pump draws from the bottom of the radiator so water is always available (assuming a nearly full to full levels) at the pump intake.

Just curious.

Just finished this rather prolonged process myself. In my case I started with 12 gallons of distilled water. I drained the radiator and refilled with the distilled water, drove the car to work and repeated the process until the water ran clear. Took about ten days total.

The top of your engine is lower than the top of your radiator?

Thats the MAIN thing that's different from the "old days"

I'd purge just as the thermostat opens.. But like I say, it has to be at a point higher than the thermostat, without an "arch' in between

Richard opined in news:z8Xkd.196778$Pl.85973@pd7tw1no:

Well, I had to go and check. The relative height of the radiator cap vs. engine height on all three vehicles in my garage are higher than the engine (excluding the intake manifold). However, on two of the three, the top of the radiator was not but the bleed/overflow from the base of the cap is higher. The cap BTW is not always on the radiator. The three vehicles are: '94 Mustang GT, '00 Durango 5.8L and '95 Intrepid.

I would believe that the bleed/overflow point is always higher so as to ensure that any trapped air is expelled..

Notwithstanding, there are many places that can form air domes that can be difficult to purge. These can be exclusive of areas serviced by purge valves or other openings.

In many modern body styles, the heater core has become the high point and is usually bereft of any bleed fittings. This leaves us with our God-given sense to tell us if the system is purged or not.... the thermostat needs to be open (the hose from the thermostat housing to the rad is hot ... notice I didn't say 'top' rad hose - reverse flow cooling systems are on the market)..... the heater must be producing heat at idle...... this is why that 15minute thermostat change costs nearly an hour....

Once a modern cooling system has been opened, it can be difficult to re-establish flow through all areas of the system...... there's nothing wrong with DIYers performing these types of service operations but it is important that they don't stumble in blindly. There are all kinds of gotchas lurking in our cars. Looking at the task logically and analytically will help get us through these situations.

In the 3.8 V6 there's plenty of places for air to hide. Even with the purge valve on top of the intake, near the thermostat, it can be a pain to get all the air out. Today I completed my cooling repair but will continue to open bleed valve and top-off radiator a couple more times over the next few driving cycles. Even with using the bleed valve, and leting the thermostat open and checking for good flow, air manages to be trapped in upper hose or somewhere else. (also I have heater on) I ran a couple weeks with clear water to make sure the radiator, top and bottom hose and thermostat replacements had no leaks. Had to go through this "purge" cycle then as well.. Make sure you have tight fit on hose going to your reserve tank as any loseness in fit will allow it to suck air rather than coolant... Chuck

Well, unless you take off the reservoir, or siphon it out, you can't really drain it. What I did was I pulled the little hose off that goes tot he radiator and just put the hose in the reservoir to flush. Leave remaining water in there, it's not much compared to the remaining water in the cooling system.

I've used prestone cleaner, it probably doesn't matter much. It's just some acidic fluid that removes scaling. It's much more important to flush the stuff out well after it's done it's job.

Don't bother. You can but its more hassle than worth it. What I Did was I removed the lower radiator hose so a lot of water could drain out the block.

Radiator, and fill the reservoir to max or a little above since you'll have some air come out for a while.

just squeeze the hoses a bit when filling/running it.

Nope, do 50/50. It's also there to prevent corrosion.

I would replace the thermostat at the same time. cheap and can save you tons in repairs if it fails. make sure you get the little gasket with it and do not overtighten the bolts for the thermostat housing. Before you flush, just take out the old thermostat, bolt the thermostat housing back on without thermostat, then add the cleaner and run the engine. This way you won't have to wait constantly for the thermostat to open when you start flushing out with clean water to get the cleaner out. then once you are done flushing the system, get as much water out as you can (radiator/lower rad-hose), bolt everything back in place (incl new thermostat and lower rad. hose. Then add half th capacity of your cooling system in coolant, fill the remaining with distilled water. Drive it for a while but keep checking the reservoir after every trip for a couple weeks. There might still be air coming out, slowly taking up all the coolant from your reservoir.

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