Coolant flush

Can someone point me in the direction of a how to? I would like to get all the 18 year old Dex-slime out of the system.

Thanks, Jon

To get all the coolant out you have to pull the 2 knock sensors, one on each side of the block.

Be careful using a chemical flush. They often result in the water pump seals leaking.

I believe that the knock sensor is on one side and the sender for the temp gauge is on the other. You still have to remove both.

Fred Kiehl wrote:

Be careful using a chemical flush. They often result in the water pump seals leaking.

I believe that the knock sensor is on one side and the sender for the temp gauge is on the other. You still have to remove both.

LT1s have one on each side of the block, sensors are in the passenger head and water pump

IMO if your water pump leaks after using a mild chemical flush it was bound to die soon anyways.

You can drain all the fluid and then add clear water and cheap food grade citric acid. then run it thru a full heat cycle or two before draining. best done in the summer months in a cold climate. I did several other clear water flushes afterwards. I had to back flush the heater core on mine to get it unplugged.

someone on here with much more LT1 experience than I said they plug often due to the reverse flow cooling.

Oh man as I kid I did it all wrong....

We used to drain as much of the fluid as we could and then filll it full of hose water. We would start the engine and keep the pet-cock valve wide open with the hose running, until everything ran clean.
Drained it 1 more time and then filled it with fresh fluids.

Looking back that was pretty dumb. No telling how much of that ended up in the ditches and possibly killed small animals. Not to mention any internal engine damage.

So how do you properly flush your fluids......not my way.

I've been there too bob, though in NJ the glycol was probably far less toxic than whatever the fish were already swimming in. Perhaps even refreshing.

I was able to recover most of the coolant with a big drain pan, and it took a lot of back-and-forth flushing to get the heater core cleared out, but it was so full of rust I ended up changing it anyway. And the rad too.

I found this thread:

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The last post says this:


Unhook the return hose (top) from the radiator and put a hose in the radiator. Start the car (and heater on FULL HOT) and let it heat up. When it runs clear, you are done. turn off the water and run the engine until water stops. turn off engine. fill with pure coolant. Should end up with 50/50.

Can it be that simple?

rjathon wrote:

Can it be that simple?

It "Can" be that simple, if that's all you want to do.  That's the way we hillbillies have always done it.
There are other ways which are preferred for a variety of reasons, some of which you see discussed above.

Doing it that way releases poisons onto the ground, storm drains, and the environment in general, and is a danger to pets and kids.
Cold water in a hot engine has risks, and Thermostat may block flow.
Some even insist on distilled water (a little to picky if you ask me, but there is a chemical explanation). Chemical flush solutions are available.
"Back" flushing is popular, said to remove more contaminants by reversing flow.
Heater cores may warrant more specific attention.
Pulling the stops can be more thorough, and make purging air from the system more thorough when you are done.

Search the posts (here and general posts on line that apply to all cars) and decide what you are trying to accomplish and how much effort you want to apply for superior or specific results.

On the Buick Roadmaster forum Buickwagon wrote up a "How to flush your heater core" thread which included pictures and it is superb. With that info an idiot can get the job done.

It would be wonderful if someone would write up a "sticky" about flushing out our cooling systems complete with pictures and written on a level that assumes complete ignorance on the receiving end.

It seems to me that this needs to be done on a regular basis and that if it is in good shape to begin with a more simple method can be employed. If the system is in bad shape perhaps one should pay a professional to get it done the first time and then a easier way could be done at home for regular upkeep.

I have always wondered why there are not coolant filters.
Diesels have them, the Mustang enthusiasts have one.  The B-Body guys used to use one from John Deere tractors, but I guess it was subject to failure and is no longer on the market.

It seems like that would save a ton of grief, particularly for heater cores, by the time a car gets to be the age of our wagons.