flushing out dexcool

[hammer]

I have to change intake gasket on my 96 4x4, 5.7, and I was wondering if I should change from the dexcool junk that caused it to leak to start with. Should I flush it out before I take the intake off , or after, or just stay with the dex. truck has 71,000 miles on it.

[Jet-X]

I doubt the Dexcool caused your failure. Most 5.7L engines will eventually leak at the corners of the intake gasket. Mine started at 70K miles, as well.  Dealer claimed the head gaskets were over torqued during assembly.  Others reported warped heads. Whatever the cause, it's a labor intensive fix. If you plan on doing it yourself, have the heads re-surfaced and count on spending an entire weekend to do it.  Here's a few good articles to read regarding Dexcool.

 

http://www.imcool.com/article....ner.htm

 

http://www.imcool.com/articles/antifreeze-...ol-macs2001.htm

[MarkD]

If you go back w/ DEXCOOL, use distilled water, not tap water.

[CMNTMXR81]

Dex-Cool has no cause to intake leaking.  That's a common problem on 5.7's due to poor design.

 

I for one would stick with Dex-cool even though I'm not a big fan of it personally.  But if you want to go to Ethylene Glycol (the good green stuff) it will require a complete and thurough flushing of the entire cooling system.  To me, more trouble than it's worth.

 

And Mark, I thought it was the other way around, with Dex-cool DO NOT used distilled water.  I thought it lacked iron or some other chemical that would cause it to boil itself off and evaporate and therefore introduce air into the system therefore not cooling effectively.  But I don't recall, maybe it is the other way around.

[mnstrmdnss]

dex-cool coolant(phosphate free) is far superior to the green stuff(ethylene glycol) in that the coolant protects aluminum parts better than the green stuff. and to end argument, u can get dexcool premixed with water, or you can get mineral free water  for adding to coolant thru auto parts stores like pep boys.

oh, and get a new radiator cap, also. cause they go bad easily and unless you had a Stant coolant system pressure tester, youll never know if its good or bad. if the cap wont hold its assigned pressure, then youll get air in the system.

[CMNTMXR81]

Dex-Cool isn't as thermally efficient as ethylene Glycol though which is why I'm not a big fan of it.  On a high compression motor that can become an issue.

 

I could care less about how insignificantly better it may be at protecting parts cause I don't let it go 100,000 miles before drain, flush, clean and refill.  Matter of fact, it'll probably have gone through that process 3 or 4 times by the time the odo hits 100k.

[bowtie_pasta]

Dex-Cool isn't as thermally efficient as ethylene Glycol though which is why I'm not a big fan of it.  On a high compression motor that can become an issue.

 

I could care less about how insignificantly better it may be at protecting parts cause I don't let it go 100,000 miles before drain, flush, clean and refill.  Matter of fact, it'll probably have gone through that process 3 or 4 times by the time the odo hits 100k.

CMNT, I'm curious as to exactly how you do this?  Could you write up a little process?  I mean, I've done it on my truck (with the green stuff), but I just want some tips on the best way to flush ALL old fluid out and refill with the proper ratio.

 

Thx

 

later

[CMNTMXR81]

I prefer to do it with a Bilstein flushing system.  A thing the dealer or a shop would have.  It pressurizes, cleans, and purges the system.  From their you can put in the old stuff.

 

Doing the old fashioned drain, flush and fill in your driveway may not get everything even if you run your heater.  It'll get the majority, but probably not everything.

 

Also, it may not necessarily be called "Bilstein" flush.  It'll be a cooling system power flush essentially. Personally, I don't think it's worth it to flush and go back to Ethylene Glycol unless you are running a high performance combo of some sort.  For an everyday vehicle, the Dex-Cool will be more than sifficient.

[bowtie_pasta]

Thanks!  I'm fast approaching 100k on my 97' Blazer and I really want to flush all the old dexcool out.  I think I will have my shop do the "power flush" and refill with dexcool.

[Firetiger(MN)]

My buddy just found out that he has a leaking intake manifold on his '98 5.7L.  Is this something common with these motors?  He has 60K on the truck.  Just like some info for him.

 

Thanks

[CMNTMXR81]

Yes, very common.  Matter of fact when I was playing around with a Tech2 on my truck a week or so ago, a Suburban was right next to me getting it's intake done.

[denali_dave]

My Denali just had it done at 67K. It took the dealer all day and it was $500.00. It sounds like its a real pain in the a$$. I have heard its a common flaw and that once its fixed you wont have to do it again so we will see.

[cyrylyn]

Dex-Cool isn't as thermally efficient as ethylene Glycol though which is why I'm not a big fan of it.  On a high compression motor that can become an issue.

 

I could care less about how insignificantly better it may be at protecting parts cause I don't let it go 100,000 miles before drain, flush, clean and refill.  Matter of fact, it'll probably have gone through that process 3 or 4 times by the time the odo hits 100k.

---

I for one would stick with Dex-cool even though I'm not a big fan of it personally.  But if you want to go to Ethylene Glycol (the good green stuff) it will require a complete and thurough flushing of the entire cooling system.  To me, more trouble than it's worth.

And Mark, I thought it was the other way around, with Dex-cool DO NOT used distilled water.  I thought it lacked iron or some other chemical that would cause it to boil itself off and evaporate and therefore introduce air into the system therefore not cooling effectively.  But I don't recall, maybe it is the other way around.

CMNTMXR81,

 

There's some things I'd like to clear up:

 

1.  Dex-Cool has just as much ethylene glycol in it as the green stuff.  Dex-Cool lacks silicates.

 

2.  The thermal efficiency of the coolant is dependent on the ratio of antifreeze to water, and the amount of pressure put on the coolant mixture.

 

3.  Dex-Cool does not have an insignificant benefit of protection.  The green stuff with eat aluminum parts.  I have a Vortec head, which is cast aluminum.  Anything OTHER than Dex-Cool will damage the head, immeadiately.

 

4.  Yes, if you switch from Dex-Cool to the green, you must totally flush the system, which you can do using pure distilled water.  Drain the coolant, put in the distilled water, drain, and repeat until it's clear.  This procedure is detailed in the Service Manual.  Distilled water is IMPERATIVE because it has no minerals or chlorine in it.  If you make tea from tap water, you'll see SCALE in the kettle after use.  If you use tap water in your engine, those same deposits will be left there.

[SoMnDMAX]

Replacing the gaskets isn't too bad of a job. Just finished up the Folk's '97 Tahoe. Took just under six hours start to road test.

 

The gaskets broke, allowing the silicone rubber sealing beads to relax. The Dexcool absolutely does not contribute to them leaking.

 

More/less a great idea, but a poorly thought out gasket design. The Vortec intake bolt scheme is so much easier to deal with than the old style, but it's too bad the gaskets aren't up to snuff.

[Black02Silverado]

Intake leaks on these engines isn't just a common problem with them but with the 3400 as well. I'm finding that out with our Venture. It is like the engineers drew up the plans for their engines on a Monday morning or something. We shouldn't be having this problem.