DEX Cool (Internet Information Overload)

[joneserr]

Ok, I have a 1999 K1500 Suburban 5.7 base model.

This truck is stock and I have all service records since it was a government truck and believe it has always had DEX Cool. The cooling system is Swiss Cheese. Started with heater hoses at heater core leaking (replaced). Then water pump (replaced) now after pressure testing Intake Gasket leaks at rear of engine.

I did not bleed the system properly on the first heater hose repair (now have a Spill-free funnel). So I might of entered air into the system and might of caused all this for my stupidity here

Now I am going to replace the intake gasket and the quick connect thing to be safe.

Should I put Dex Cool back in (been using Prestone Dex Cool) or flush and put Prestone Extended Life? I read that Dex Cool issues have been fixed, but might not be compatible with 90s vehicles but works well with newer models.

Also, intake manifold job looks doable for me just concerned about getting the distributor back in correctly.

Thanks!

 

[Stepside_fever95]

My 1999 K1500 Suburban 5.7 has always had prestone extended life ran in it since it was in my family in 2002. I did the intake manifold gasket a couple years ago, and it is pretty straight foward, just a bunch of wires to disconnect and a few brackets that are hard to reach. When i put the distributor back together, i had it one cog off and it ran fine other than a few misfires at around 3500 rpm. Everyone claimed it was the spider injectors but after checking, the distributor was off. Theres a good writeup on setting it properly on gmtruckcentral. Good luck with it and hope this helps.

 

[df2x4]

Personally I don't mind Dexcool. I've seen horror stories about what it does to certain people's cooling systems, but both of my trucks have been in the family since new and I've never had a single issue. I'm of the opinion that if you actually maintain your truck then it really doesn't matter which coolant you use. (As long as you don't try and mix two types together. ..)

 

[Ironhead]

Plus one to df2x4. When I got my 98 5.7 litre, it had been well maintained, and it had green coolant. Since I couldn't be sure how old it was, I decided to flush it and put in new green stuff. It looks as though there has never been any cooling system issues with this vehicle.

Having said that, I think it's important to change the fluid out every two years, as it is not really a long-life product like Dex cool is supposed to be.

 

[joneserr]

Thanks for the replies. I think I might go with Dex Cool for a year or two since I it is new stuff and have extra and then swap for green.

Any tips on getting the distributor back in correctly? Looked at some videos but concerned I am not going to get the timing back correctly.

I see how you set #1 to TDC, set the marks on the distributor to count for rotation and move the oil pump to align before setting it in. However even after this seems like timing can still be off in the computer and might have to have a shop reset the timing? I guess the check engine light will let you know?

 

[mattillac]

Original owner here, my 1999 5.7 has always had dex cool.

After replacing the crummy original intake gaskets, I stuck with it.

Before pulling my distributor I thorughly marked its original positioning and then reinstalled according to those marks.

Wil you be using fel-pro MS98000T gaskets and replacing that GM quick connect fitting with a simple hose barb and hose clamp setup ?

 

[21Actual]

Original owner here, my 1999 5.7 has always had dex cool.

After replacing the crummy original intake gaskets, I stuck with it.

Before pulling my distributor I thorughly marked its original positioning and then reinstalled according to those marks.

Wil you be using fel-pro MS98000T gaskets and replacing that GM quick connect fitting with a simple hose barb and hose clamp setup ?

Thats what I did with my dizzy when I did the intake. I iddnt bother with seting TDC, just marked rotor position with a sharpie in both the seated position and its location when lifted out enough for the gear to release, and then on the base with a paint pen. Then borrowed a scanner to do the CASE relearn afterwards. I diddnt get the code for it, but since the dizzy was removed I opted to do the relearn anyways.


Using the green long life coolant myself. Ill just change it out every few years.

 

[joneserr]

Ok finished the job was not easy but I have a garage and this is not my daily driver. Put the upgraded felpro gaskets in and a new Delco fuel injection spider cleaned everything up and also install new intake bolts and torqued per the manual. Pulled both valve covers and looks like I was getting some water into the oil but I think I caught it in time.

I put the #1 to TDC and marked and pulled the distributor. Was a total pain getting it back in the correct way but started on first crank. I had to turn the oil pump with a screw driver to get it back in at the correct spot. A friend my be able to help reset the timing with a computer program.

Tried finding a barb for quick connect but could not find a 5/8 thread to 3/4 barb at Home Depot so bought a new quick connect at AutoZone.

I put new heater hose on the heater core where it was leaking out of what looked like a bad OEM clamp. But still leaks from the end of the hose. Tightened some more on the clamps. Hope I don't have a bad heater core now that would really put me over the edge.


As this thing seems to leak all over the place, water pump, radiator, intake gaskets, heater hoses I am starting to wonder about Dex Cool. But the truck is almost 20 years old. I am leaning towards green long life coolant now.

 

[df2x4]

If you have a lot of leaks you don't plan on fixing immediately, then the green stuff may be a better choice. Dexcool doesn't play well with neglected cooling systems and unexpected air pockets from what I've read.

 

[joneserr]

Thanks I am really leaning to green long life stuff. Mine has the rear heater (Suburban) so might be difficult to get all the air out. I am using a Spillfree funnel and running the air out first.

Any suggestions on flushing? To not introduce tap water I was thinking of first draining and refilling with distilled water until it is clear than putting the green in to get to 50/50. This make sense?

Do you think a leak at the heater core connection with the hose might indicate a crack in the heater core pipe? Leaks after I replaced the clamp and hose but did look like the OEM clamp was not clamping over the hose correctly.