Best flush.

[T-Keith]

I'm looking to flush my cooling systems. The one on my L67 is especially important as I want to make sure the knock sensors are clean. The heater core also may be clogged.

Prestone sells a flush and a cleaner. What would be the best to use?

-T

 

[Matt_S]

The Prestone cleaner is definitely stronger than the flush. The flush stays in for 15 - 20 minutes, you leave the cleaner in for several days. I believe there are stronger products available as well, but I'm not familiar with them.

 

[paulo57509]

There used to be some pretty good flushing agents on the maket, but because of recent environmnental concerns, I don't see them any more. Permatex used to make some stuff that required a neutralizer after use. I don't see this stuff anymore either.

In my experience, Prestone cleaner won't do much with a neglected cooling system. I've left it in the cooling system of my old Pontiac Phoenix for a couple of weeks (did it twice) and it didn't do much but turn a rusty brown color. Didn't remove much (if any) rust or scale from the radiator.

Knock sensors? I take it that the knock sensors do double duty as engine drain plugs? Since you're going to be draining coolant anyway, why not just remove the sensors and mechanically remove any deposits?

 

[T-Keith]

Good idea, but the sensors are hard to get at, especially the back one, being between the engine and transmission. The cooling system hasn't really been neglacted, at least not since I've had it.

-T

 

[Ray H]

Are these little piezo-crystal "microphones" really exposed to engine coolant? Why? (Seems to me the metal of the engine block would carry the audible shock waves of pre-ignition just dandy dry...)

 

[XS650]

quote:

---

Originally posted by Ray H:
Are these little piezo-crystal "microphones" really exposed to engine coolant? Why? (Seems to me the metal of the engine block would carry the audible shock waves of pre-ignition just dandy dry...)

---

Good question. I doubt that they really need to be exposed to the coolant. They might be where they are because the holes in the block were already needed to be there for drain plugs so they were free for the knock sensors. It's also a few time cheaper to make a tapped through hole than it is a short blind tapped hole.

I didn't look that closely at mine when I had them out a couple of weeks ago, but the body (1/4 pipe thread)and end that screws into the block seems to be one piece, so I doubt the piezo element is actually directly exposed to coolant.

 

[mf150]

Urine= Uric Acid

 

[Kestas]

I'm guessing these sensors are installed into through-drilled holes as opposed to blind holes simply because they're easier to drill.

Then again, cast gray iron does have acoustical damping properties.

Also, there should be no environmental concerns with Prestone cleaner (or flushant). It contains citric acid, which is not an environmental concern at all.

 

[T-Keith]

From what I've been told the knock sensors are exposed to coolant on my model.(97 GM 3800) Although on the older 3800 it was not. Perhaps the coolant provides some sound transfer, I'm not sure. Perhaps the best location(on the block close to th heads) just happens to have a coolant passage there.

Back to the subject, which of these cleaners is the better of the two?

 

[trynew]

This will probably sound bizarre, but I drain the system, fill it with clean water, run the engine, drain it again, then put in a half cup of Cascade (automatic diswasher power, the kind with no chlorine), fill it again with water and run it for a few days. Then, I drain it, and if the water is still dirty, I keep repeating the Cascade treatment until it gets acceptibly clean. Then I flush it again a few times with pure water and finally put in the antifreeze/water solution.

This doesn't remove the rust and mineral corrosion, but it does remove greasy dirt. Cascade is low suds compared to the hand dishwashing soaps like Dawn, so don't use the hand ones. They will suds too much.

The slipperiness of the soap probably helps keep everything lubricated in the cooling system until the antifreeze is back in.

This takes a lot of patience. Be sure to let the engine cool before putting in cold water! Also, don't try it if there is any possibility of freezing temperatures before you get the antifreeze back in.

 

[Kestas]

Not at all bizarre. Mercedes has a similar procedure for head gasket replacement after oil has gotten into the cooling system after head failure. It's well-known on the Mercedes newsgroup.

 

[Matt_S]

The dishwasher detergent makes sense. I think it's important, though, that you're using a non-chlorine detergent. Most detergents contain bleach, especially the liquids, you have to be careful.

 

[New]

don't forget to properly torque the knock sensors when mounting them back. Too much torque and they'll declare every shock a knock; less torque, they'll ignore knocks.

 

[T-Keith]

So I checked out the Prestone flush and cleaner. Both contain citric acid. What's the difference besides application method?

-T

 

[HerkyJim]

On my '72 Valiant 318 I tried flushing radiator to cure a mild overheating problem. Flushed it THREE times with Prestone stuff the kind you leave in for several hours driving. Probably hundred gallons of fresh water through the fitting-in-the-heater-hose "flush" setup. Waste of time and mess for nothing. Had radiator recored and problem disappeared.

My $0.02

 

[XS650]

quote:

---

Originally posted by Matt_S:
The dishwasher detergent makes sense. I think it's important, though, that you're using a non-chlorine detergent. Most detergents contain bleach, especially the liquids, you have to be careful.

---

Dishwasher detergent is an alkali and corrodes the crap out of aluminum. Not good for aluminum heads/blocks, alot worse for aluminum radiators.

You probably won't destroy your radiator with one or two applications, but you will take alot of life out of it. Wash a piece of aluminum in a dishwasher and observe.

 

[roman]

ok, for the flush, what you want to do it just remove the top hose to the thermostat housing. Then buy a cheap hose, or even an old one and connect it to the housing (its goota be long because what you want to do, is to get the coolant away from the car, BUT THE HOSE IS AN OPTION, I DIDNT use it when i did my flush, just let it drain wereever. Get two houses from your house (garden houses) with the metal ends removed and ram them in the original rad hose turn those two hoses on full pressure, and make sure noone in the house is using water, you want maximum pressure here.

**** , i forgot to mention, remove the housing aswell, and take out the thermo.

Now, turn on your car and let it idle, and turn on your heater full blast.keep walking back and forth from the engine bay and to your car looking for anything akward. Make sure that low coolant light doesnt turn on. Do this for about 15 minutes, then shut the engine off. Remove the two hoses, and get a buddyd to begin pouring distilled water into the rad hose through a funnel. Pour in a bout 12 litres. You have to turn the car on and off to get the old water out (garden hose water), but you cant let the system run dry either. Now add about 1-2 liters off halvoline dexcool. and topp everything off with distilled water. Drive the cxar aggressivly and get the engine coolant hot, and dont forget to roll down all four windows and turn the heater on. You want to get out as much crap out of the engine as possible. Do this for about a week. Once again, i forgot to mention, put in the thermo (195) before this.

After a week , repeat the funnel and a frind thing with distilled water. but let the rad empty out a bit, beacuse you need to get 7 litres of dexcool in their (7:6 ratio), then top off with pure distilled water, and make sure to turn the heater on to get everything in their. If you are trying to battle KR (knock retard) i would recommend going to intense-racing.com and order a 180 thermo from them. Many gtp's on www.clubgp.com run a 180 thermo to keep temps and kr fdown, and performance up. The reason why a recommend buying the thermo from intense racing, is beacuse i bought two 180's already, one from partssource, and one from napa, and both stuck open in two weeks. i have one year on the 180 from intense, and its still fine.

If you ever have gp specific questions, go to clubgp.com, anyone will help you with any problem you have their.

forgot to mention, i wouldnt remove the knock sensors unless you have noticable sludge in the engine, but even then, their is no point in removing them.