To flush or not to flush, plus spark plugs ?

I've been reading mixed reviews all over the net about flushing a cars engine and other parts. However tonight when I was burping the radiator, noticed a lot of brown pastey sludge caked to the cap. I'd like to get the radiator flushed, but my neighbor said the sludge is likely coming from the engine as well.

Has anyone here ever had any problems after flushing their engine or radiator?


also- my car is a 2006 and I doubt the previous owner ever got the car a tune up. Since 2009 when I bought it, I havent had a tune up either. So I was thinking maybe its time for one. The engine still sounds like a gentle hum, it doesnt have any back firing or anything. I was looking at getting some spark plugs and having my neighbor install them but theres so many different kinds. The cheapy ones at 3 bucks each, or this "Iridium" plug thats about 10 bucks each. Anyone have a recommendation? taking it to a mechanic is not an option right now which is why i am looking at having my neighbor do it and I'll watch and learn.

** I've decided to use an engine treatment additive rather than flush it. I do plan on flushing the radiator though.

I wouldn't waste your money on $10 plats. Cheapy's will be just fine for a daily driver. All plats really get you is some increased life.

As for flushing, I definitely recommend flushing the coolant system. As for the engine additive, I wouldn't worry about anything in the crankcase other than oil. Oil additives are gimmicks and are sometimes more harmful than helpful.

Whatever plug is in there, replace it with the same OEM part.......also, pulling the wires off the rear plugs can be tough......sometimes they feel like they are baked on....more often than not, you can damage the wires taking them off, causing a misfire down the road.......would replace the wires, too....check the coil terminals for "corrosion" or arcing marks....

You are at the 5yr/150K maintenance as far as coolant goes.....that crud on the rad cap forms when there is air in the system......I would flush the whole system.....would also replace the thermostat(which makes it easier to flush the system)....after 5 years, they were known to set a P0128 code.....

I have read many times that the 'crud' in the cooling system using 'dex-cool' is caused by air in the system.
isn't the system vented to the atmosphere throught the expansion tank? isn.t there always a pocket of air above the coolant mixture in the expansion tank? doesn't water have dissolved oxygen in it, besides being made up of oxygen in the chemical formula?

there must be more factors involved with 'crud' formulation than 'air in the system'.

The expansion tank it just that, expansion. The coolant system itself is sealed. When you keep your coolant tank properly topped off you won't get air into the system because if the coolant is needed then vacuum will draw the coolant into the radiator. The only way it will get air is if the overflow tank is too low.

Think of it like bleeding your brakes one man style. You have a bottle with fluid in it (a resevoir if you will), run a tube from the brake bleeder to the bottle. When you press the pedal fluid will "expand" into the bottle. When you let off the pedal fluid will be drawn back in. There is a layer of air on top of bottle, but that air will not get in.

the system is not closed as it is vented to the exapnsion tank via the radiator cap. this venting does take place to the very bottom of the bottle
which as you said should be keep full to the cold line or a bit higher.


air on top of the coolant in the expansion tank has no effect on the fluid.
same air in the system has an effect.
as asked earlier there is dissolved oxygen in water as well as part of its chemical make up. does this have an effect.

there is more going on here than air. i am convinced that the loss of coolant and the repeated refilling of the system instead or finding and repairing the leak has some effect here.

with low coolant internal engine parts( cast iron block,etc.) are exposed and become dry and oxidize. as the coolant is refilled and covers these previously exposed areas this oxidation is washed off and enters the system.

if this occurs enough times you have "crud". also as someone else ststed the coolant must be changed at the end or near end of its service life. this closes my input on this matter.

The system IS sealed. If it were not then overheating would occur. The cap is pressurized. If it weren't sealed then there is no way the system would hold pressure.