Dex Cool replacement

It's almost has been proved that using dex-cool antifreeze will eventually lead to intake manifold problem in some GM models (including Montana).
I want to flush my cooling system in my Montana 2000, then replace the dex-cool with the regular green antifreeze, is this going to create a problem?
And will this save me from the intake manifold problem?
Your comments are highly appreciated.

Green is fine as long as you COMPLETELY flush the Dex-Cool out. Combining the two can cause gelling. I doubt this will save you from the manifold leak problem, but maybe someone else on here can verify this.

The guys at Sangster Motors (who seem to know their stuff) say to change back to the green coolant because it's less corrosive. (?!!)

I think the problem with the lower intake manifold gaskets on the GM 60 degree V-6 is due to the bolts coming loose.

I bought the GM gasket set; there was an instruction sheet inside that said to replace the lower manifold bolts with some new ones that had a different thread locking compound on them. Also, the outer 4 bolts were to be torque'd to 25 N/M, which is about twice the original torque value.

I'd say you're safe to have it flushed and filled. :smokin:

Edit: Oh yeah, I tore mine apart because it was leaking. And those 4 outer bolts were so loose, I didn't have to use a wrench on them. Just removed them with my fingers. :uhoh:

If you don't have any problems right now, I'd sure have those bolts checked and torque'd down!!

It has never been proven that Dex-cool causes manifold leaks.

It has never been proven that Dex-cool causes manifold leaks.


And my (limited) personal experience indicates that it's the bolts, not the coolant, that causes this particular problem. (I put the Dex-cool back in mine.)

The dex cool should have better corrosion protection than the "green" stuff. And it is not the cause of the intake leaks, poor gaskets are the cause.

Thank you all guys, I was kind of unbelieving that dex-cool creating that problem since it doesn't create it in some other GM engines. I'll try to get those loose bolts replaced, however I think it'd probably cost almost the same as replacing the gaskets.
Is there anyone knows if replacing the bolts is an easy job or it'd take the same man-hours as replacing the gasket? (I know Dan_in_WA knows for sure since he did this job before), Thank you all in advance.

If your going to pull all those those bolts you might as well replace the gaskets also it wont take that much longer except cleaning every for reassembly.

Oh Also on mine I used alittle dab of red locktight to make sure those bolts dont come loose again.

Oh Also on mine I used alittle dab of red locktight to make sure those bolts dont come loose again.

Yeah, apparently the only difference between the "New" and "Old" bolts is the threadlocking compound.

As far as changing the bolts, I wouldn't bother unless changing the gaskets because of the leak problem.

What you can do right now (and I'd do it) is get down in there with a 10mm socket, or wrench, whatever fits, and just make sure that the bolts are snugged down good. It will be obvious if they're loose.

If all is well, I wouldn't worry about it.


EDIT: My opinions and advice have changed a little throughout this thread, since I'm still learning as I go. :smile:

I've dona at least 300 manifold jobs in the last couple of years. It can be done in 2 hours if you know what you are doing otherwise about 6 hours.

Hi Flatrater:

The owner's manual says that the system holds 11.3 liters (with rear heater).

In order to get a 50/50 mix, (I assume this would be good to about minus 35C, yes/no?); - once I back-flush the system, should I add approximately 6 liters of Dex-Cool and top up with water, or....?

Your advise?

You'll never get 11.3 liters (~3 gallons for those of us that are metrically challenged). If you get 2 gallons worth, you will be lucky. There are many water passages and coolant lines that don't drain. For instance, the front and rear heater cores, their supply lines, and the block all hold a significant amount that won't usually drain out when doing your intake.

When I did my intake last year, I just about 5 quarts 50/50 mixed. When I did my heads a month or two back, I put in just over 2 gallons 50/50 mixture and that was with removing the two block drains as well as getting a decent amount of the exposed heater core lines empty (I changed some of the clamps.

I'd start off with the backflush, drain as much as you can with removing the two block drains, then close up the system. Add a gallon of pure antifreeze, then partially top off the remaining amount with 50/50. Run the system briefly to get things mixed up and check for leaks. Test the coolant mixture for the correct freeze/boil over points, and adjust as necessary to get around 50/50.

Just so you are clear, I'm only trying to do a five-year flush and fill, not an intake repair (I hope!)

....You'll never get 11.3 liters (~3 gallons for those of us that are metrically challenged). If you get 2 gallons worth, you will be lucky...

Acknowledged....Hey, you got to love GM, afterall they built a metric van (ie bolts, fasteners, etc) probably so that all the good techs would have to go out and buy new metric tools (us backyard folks too!)

...I'd start off with the backflush...

OK...and just how would you do that on this @#$%^&* blessed van?

.

Just so you are clear, I'm only trying to do a five-year flush and fill, not an intake repair (I hope!)
.
I sure hope you aren't planning on waiting another 5 years to flush and fill your van. It has been found that the original reccomendation of 5 yr/150k interval change does not work and instead a 2 yr/ 30k mile coolant change is a better choice. This lessens the chance of the DexCool from being contaminated and gelling up on you. While you are at it, it is a good idea to change your radiator cap while you're at it as this has been found as a potential source for contamination as they age.

I wonder if the dex-cool will degrade my upgraded lower intake gasket. I think I'll wait till it's off warranty to switch back to green.

btw...what do you do with the old dex-cool??

As to recycling it, recycle it in the same manner you recycle the green stuff. Some autopart stores will take it. My local government and trash company sponsor a tox-away day that will also take it. Yours might have something similar.

As to degrading your intake gasket, it won't do anything. There are a lot of urban legends about Dex-Cool and what all it does or doesn't do. The problems with our van and the intake gasket isn't the coolant, but rather the gasket and the bolts. Replacing the gasket and bolts with the updated specs should solve the problem, no matter if you are using dex-cool or regular ethylen glycol.

The only problem with Dex-cool is that people don't pay attention to their fluids. When air gets introduced into the system, it causes portions of the coolant to crystalize or otherwise form the gunk that plugs up the system. This decreases the performance of the system, but isn't itself going to cause a gasket leak unless the plugged up portion horrendiously bad. If that was the case, you can hardly fault a gasket for not being engineered for a catastropic problem like that.

As to flushing the system, the proper way to flush it is to remove the thermostat and back wash everything, hooking up a hose to the upper radiator hose and eventually letting the water run out of the top of the radiator. If you were just talking about a chemical flush where you drain as much as you can, refill with water and the detergent, let it cycle, then drain it, I would follow the instructions still, repeat it again with plane water to get out as much of the chemical as possible, drain the radiator and the two block drains, then follow the rest of my instructions. But that's just how I would do it.

...As to flushing the system, the proper way to flush it is to remove the thermostat and back wash everything, hooking up a hose to the upper radiator hose and eventually letting the water run out of the top of the radiator....

Sorry, no adventure left in these bones, I guess. Took it in this morning and let the shop power flush it and re-fill it too with new Dex-Cool. It was worth the $75 (no agrevation!)

.

""" OK...and just how would you do that on this @#$%^&* blessed van?"""

Directions please LOL

Please star a new thread with your inquiry instead of bringing up an old 3 year old thread that hasn't seen action in 2 years. Our handy dandy AF guidelines spells it all out. (Just click on the link in my signature).
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