1999 Z/28

[wxo]

Well, the honeymoon is over!! I began to notice a moaning kind of noise on startup that goes away after a short time. I haven't been able to pinpoint it yet, but yesterday I thought it might be coming from the area of the water pump. So, I decided to check the coolant level. First, I looked for the normal sight markings on the reservoir, but this thing is opaque black. From the owner's manual, I learned that this thing has a dipstick in the reservoir. Well, isn't that interesting? Upon removing the dipstick, I saw that it was covered with this tan sludgy stuff! Looking in the reservoir, I could see more of this stuff on the inside. As you can imagine, I'm not liking the looks of this very much. From everything I've learned about the history of the car, it has been well cared for. It would be interesting to know if the coolant has ever been flushed and changed.
That question may be answered in the records from the dealer that are on the way to me (hopefully).

Anyway, I get on the web and discover all kinds of information about DexCool coolant involved in all kinds of problems with GM engines. There are links to articles about class action lawsuits against GM for engine damage relating to DexCool. Now I'm really worried. As usual on the web, there are all kinds of accusations and tales and defenses of this stuff to the point where it is difficult for anyone to know the truth.

What do you guys know about this issue? Have you had experience like this? What's the best way to clean out my cooling system of this stuff?

[wxo]

After more research, I found this GM procedure for cleaning the cooling system.
http://members.shaw.ca/betterthanyoutoo ... lflush.htm
The basic process in the TSB sounds reasonable. I doubt if I will buy new radiator cap and thermostat, though. The cooling system of the car functions just fine. I don't think the sludge has gotten to the point of causing serious problems. I'll know more when I do more hands on investigation.

[markss327]

It's my understanding that Dexcool and any gaskets, don't get along.
http://www.naioa.com, It's an Impala thing, but there are all kinds of issues with the lower intake manifold gaskets. On the Impalas, (3.4 and 3.8), April 2004 is the date when a redesign gasket was implemented.

I've read mixed reviews whether a flush and re-fill with the green stuff, is acceptable.

IMHO, I'd flush and re-fill with the red stuff, and see what happens.

[VeeDub]

I'm going to be doing a flush and refill on my car (VR6). I've heard the green antifreeze is no good for the headgasket on that engine. Supposedly it ( the green stuff)will corrode the gasket and that is why G-11 or G-12 antifreeze is recommended. Well G-11 is $22.00 per gal. - still alot cheaper than a headgasket but still... $22.. for antifreeze?? So I called Peak and spoke to a rep that assured me that there Extended Life Antifreeze ($11.00) will not harm the gaskets and is safe for all cars/trucks. thats what I'm going with. BTW Prestone has a similair product also.

[Basement Paul]

Dexcool goes bad! I've had this in both of my wife's Saturns. After about seven years, it just seems to turn to crap. In the first car I didn't really pay much attention to it and it ruined the headgasket and eventually cracked the head from overheating from having oil in the coolant. In the "newer" Saturn, after six or so years, like clockwork, the fluid turned to crap, I had the dealer flush it out, and all seems OK.
I think the coolant you can use in anything, would be better than putting dexcool back in it, but having a machine that vacuums the coolant through the motor is better than just trying to flush it out yourself in my opinion. Not to mention this is not an expensive procedure to have someone do (maybe $100 or so) and it will be done right.

Hopefully all is well and all you need is flushing.

-BP

[wxo]

After a closer investigation, I'm feeling a lot better about it tonight. With a cold engine, I was able remove the radiator cap and see into the radiator. The DexCool was clear enough for me to see the ends of the first couple of rows of tubes and they looked clean to me. There was a small amount of residue of the tan gunk around the radiator cap opening and on the sealing part of the cap. I then removed the reservoir and dumped out the contents into a clear container. The Dexcool was clear there also, but there was a very thin layer of this tan granular looking stuff floating on top. This was the stuff that coated the antifreeze dipstick. So at this point, I think I'll take BP's suggestion and have the cooling system power flushed and then replace the coolant with something other than DexCool.

[GMJohnny]

WXO ... I have several 3800 Buick engines. Recently, looking through the repair receipts that the previous owner ( Jerry Kerlin, he's nice ) gave me for my wife's LeSabre, I noticed that they ( a dealer ) used a sealant as a preventitive measure to keep the intake system from leaking. If you have never seen the GM sealant tablets, they are tan, flakey things that leave that exact tan residue in both the bottle and the radiator neck. I would think that there is a good chance that may be what your residue is. If that is the case, you may not have as much of an issue as you might think, and you may also, after a flush, consider putting them in again. They may have done it for a reason.......

[wxo]

Ya know, Johnny, you may be on to something.
I've learned that air in the cooling system may be related to the sludging problems with DexCool. GM states that DexCool systems must always be kept full...even to the point of keeping the level of the reservoir to the hot level when cold. Maybe GM is trying to mitigate the problems by making sure there are no minor leaks that would allow the level of coolant to go down. This would cause the company more sludge headaches from people who don't pay attention to their cars.

I believe you are correct about the tan stuff. It doesn't appear to be mixed with the coolant. It's just floating on top and has collected on the dip stick in the reservoir.

Furthermore, I really don't like the idea of stopleak in my cooling system.
I believe DexCool is the real problem here. I'm going to change to something else.

[Maverick]

I've been reading on the Maverick Forum that coolant should be kept full to prevent any air/coolant contact. Never thought of that as a problem, but maybe that's an issue with DEXCOOL?

Also, I know you are aware, but maybe others might not be, so it might be worth a mention here. Mixing even a small amount of different anti-freezes can cause a brown, muddy precipition in the cooling system. Radiator pro told us that was a big problem in 3.8s.

[TireSmoker]

When I replaced the water pump in my supercharged 3800 last summer, I remember reading about big problems mixing DexCool with regular antifreeze. Since I wasnt planning on flushing the whole system, I paid the extra money for DexCool coolant. So far, so good.

-Dave

[wxo]

I picked up four rims today from a Craigslist ad. They are the 5 spoke, 17x9.5 ZR1 style. They are not pristine, but for $200 I don't think I went too far wrong. They should clean up nicely and look good.

[wxo]

This is one of those "one thing leads to another" tale. It occurred to me that I need a shift light, so I started looking. I didn't really like the idea of a flashlight lookin' thing on my dash and I was a little disappointed until I learned of a device called an "RPM switch" (mostly used by nitrous guys).
Well this little box can turn on a small led "shift light" installed in any convenient place where it can easily be seen during the heat of bangin' gears. As it turns out, the cheaper RPM switches don't work with the LS1 so I would be required to spend upwards of $120 for what I really wanted to do. I might spring for it to get what I want, but I was not jumping for it.

Then I read a post by someone who was able to activate a shift light by using the car's ECM!!! Now we're talkin'! He used a spare pin on the ECM to wire in the light, but he required an HP Tuner to make the changes to the table parameters to do it. Hmmm...what's this HP Tuner thing and do I need one? I think I do...soon as I figure out what it is and how it works.

[MostMint]

The software starts at $510.25 and will get you 8 credits - enough for about 4 cars. Or you might want to find someone who already has the software and might sell you credits at $125 for two. This opens up all kinds of possibilities as you can change a lot of things. Each model car has different parameters so if someone were to master a vehicle, say an Impala SS, only some of that knowledge would transfer to the Z28.

Or you could follow GM Johnny and have someone do it professionally (Hutter uses the HP Tuner software). This will run over $500. Again you would get a lot more than a shift light wire.

I would be interested in knowing how that signal is getting directed to a wire where you can pick it up with a light.

[GMJohnny]

WXO, one tip I did get from the Hutter racing experience was that you should run a 160 thermostat. He said the engines work much better when running cool. He set my fans based on the 160 degree ( even though currently I have a 195 degree in there now ), and my next move is to put in the cooler stat. I am sure my heat won't be so good, but speed is important. On the hp tuner idea, I really doubt that anybody can "seat of your pants" their way through the computer tune as well as a dyno could. Dyno runs were expensive, but after 11 of them, somebody who had done hundreds of these tunes felt he had it right, then the dyno proved it. Food for thought GM

[wxo]

Andy, here's the link to the PCM controlled shift light:

http://www.hptuners.com/forum/showthread.php?p=143689