Coolant system flush procedure?

[firefox]

Can someone please point to the section in the TM's that discusses how to flush the complete cooling system.

So far all I have encountered is how to drain the radiator. I know from civi trucks that the thermostat will screw things up.

Any tips would be appreciated,
Thanks,
Bruce

 

[southdave]

That is good question.. I know as far back as 89 it was consider hazmat, well than again that was in california. Anyway flushing and cleaning was done with a machine. the fuild was exchange chemical add ect..
The proceedure I use is casdade dishwasher at 15 to 20% solution. I usally swap out the t stat afterward.

 

[Bighurt]

Are you asking because you think you have sediment in the system. Or are you just trying to replace coolant, and want to get all of it out. I've always been against flushing transmissions and coolant systems with the machines they use. I'm more in favor of drain and replace.

I think there are procedures in the M915 manual but not positive, and judging by your signature that's not your intended victim.

Both the M35 and M925 in my collection need a "flush" this spring. I plan to just drain the complete system, filter, test and add as necessary. With the age on the trucks I fear anything other than gravity will do more harm than good. That's just my opinion.

Good Luck

 

[firefox]

I should have specified that it was for my M1008, that's why I posted in the CUCV forum. I replaced the radiator about a month ago and bassed on some advice here I put some detergent in the water when I refilled. I now want to flush all of that out and then put water/antifreeze mix back in. My concern was that I wasn't sure where to put a hose to force water in or where to put a hose to extract the water,
and whether I had to remove the t stat.
Also, if I remove the t stat, I am going to have to get a gasket when I replace, right?

Thanks for responding to this thread, it is really appreciated!
Bruce

 

[Bighurt]

While I'm sure the SOP is to inspect and reuse a gasket. I'm always a fan of replacement, weather it be within the motor or as simple as the oil plug gasket. Most of the time they are cheap enough that even those done during periodic maintenance are just replaced. Obviously there are gaskets that have to be replaced, intake, head, but for a few cents why chance it.

Your question about where to force water in and out is exactly my point. I wouldn't force any water in the system. In my experience it just creates more issues. Now you can look at those as problems that where going to rear their ugly head anyways but most of the time if it isn't broke... My experience with tranny flushes is similar, automatic just don't seam to operate the same after a flush, sometime not for the better.

For the M1008, you can just pick-up a repair manual from a GMC or Chevy k series pickup from those years. Or take it in for service, in CA there are lots of places that do that service.

Personally I would just drain and replace. Or don't power flush; Drain, fill with water, run to operating temp, cool, drain, and fill with appropriate blend. Remember both waste coolant and water used should be disposed of IAW local laws.

Others may differ but that's my opinion. If you really have a fear of sedimentation, there are lots of aftermarket coolant filter kits. I have one for my F350. They are inexpensive and very easy to install.

Good Luck

 

[firefox]

I agree with you regarding the gaskets Jeremy. The original coolant was disposed of when I replaced the radiator, but there probably is still a little in the system. Your
idea of drain, fill, run. repeat until clear, then add 50% antifreeze sounds like the way to go. This takes care of the t stat issue and doesn't force anything in or out.

Thank you very much for your help!
Bruce

 

[Bighurt]

I found a few army manuals that refer to reverse flushing the radiator and block separately. This was done by running water against the normal coolant flow but not a pressure. This is somewhat different than what some dealers do by flushing the system as a whole, which can cause sediment in the block to lodge in the radiator.

I still think it's over the top but remember draining the radiator or pulling the lower radiator hose my not get out all the coolant from the block. I use premixed coolant but it's always a good idea after the system is full and assumed mixed to test it.

 

[Barrman]

If I understand your question correctly, you just want to get the detergent and water out. Not, force crud or gunk out of the system. The best and cheapest way to do that is to pull the upper radiator hose off at the radiator, stick a garden hose in the radiator cap inlet, let the hose flow kind of slow, fire the truck up and let it warm up to where the thermostat opens up. Increase the garden hose flow even though it won't keep up with the water pump flow. Let it keep throwing water out until you think it is cleaned out.

However, you still have the problem of needing to get all the tap water out of the system. You want to end up with a 50/50 mix of distilled water and coolant. A few post up gave the best advice, pull the bottom hose, let it drain and then fill it back up.

 

[firefox]

Thanks guys, This really helps alot. I just got a old prisim type coolant tester
so I can test the end result, but I hadn't thought about the issue with distilled water.

I have to do all my own maintenance and help like this is really incredible.
Bruce

 

[Terracoma]

...but there probably is still a little in the system. Your idea of drain, fill, run. repeat until clear, then add 50% antifreeze sounds like the way to go.

However, you still have the problem of needing to get all the tap water out of the system. You want to end up with a 50/50 mix of distilled water and coolant. A few post up gave the best advice, pull the bottom hose, let it drain and then fill it back up.

I think all of the above posts are good advice.

I'll be installing an engine block heater in my M1008 soon, and plan on doing exactly what Jeremy and Bruce are describing: drain the coolant from the radiator, then fill the radiator with distilled water, circulate, drain the radiator again, refill with distilled water again, and repeat until the drained coolant runs clear. Since I'll be removing the freeze plug to install the heater, I'll be draining most of the coolant from the engine block in the process, and I shouldn't need to refill/drain/circulate more than once or twice to get the bulk of the old antifreeze out of the system.

 

[Vhyle]

I had to replace my radiator because it had a bad internal ATF leak, so my cooling system had quite a bit of ATF contamination. I "flushed" mine out by running water through the block by pouring water down into the upper hose, and one of the heater core hoses. It got a good bit of it out, but it didn't get all of it. After a while, the remaining ATF made its way through the top and into the jug (since it floats on top), so I had to pull off the jug, empty, rinse and refill. There's tiny bits of ATF floating around in the jug now, but it's pretty much out of the system.

It wasn't the best way to do it, but it worked in a pinch. I couldn't use a running hose because 1) my dog will lick that crap up and 2) I did this in my garage.

 

[TedO]

I have a 1986 M1008 CUCV and I need to flush the radiator. It seems very difficult to get to the petcock, let alone open it. What is the trick?? What color radiator fluid do I use? What is the procedure to do the flush?

 

[Barrman]

Pull the bottom hose. That valve has been sitting in one place for maybe 30 years now. You go messig with it, it might get mad and not seal up again.