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Topic Review (Newest First)
03-19-2013 06:26 AM
MouseFink It is important to have some sort of a a restrictor in the inlet of the heat core. Ford has a restrictor in the heater core inlet hose. From 1990-2002, GM uses the plastic clip (clip only-GM 15739936 or Dorman 800-405) ) inside the quick disconnect fitting (fitting with a clip - GM 12543621 or Dorman 800-401) as a coolant restrictor. If you must remove the heater hose for any reason and damage the plastic clip, you can purchase new plastic clips separately so you do not have to replace the entire fitting and risk ruining the threads in the aluminum manifold.

Without restriction, the coolant pressure can balloon the heater core and cause the heater core to leak. The coolant pressure is especially high above 4000 RPM. I have a thick wall intake manifold nipple fitting in my parts bin. It has a 1/2" passage for the heater core inlet coolant. I purchased the mipple fitting at a local Chevrolet dealership but I do not recall what the part number was. It could be used to replace the quick connect fitting.

Many years ago, I pushed a old 1/2" drive socket in the 5/8" heater core inlet hose of my '55 Chevy. That would be called "redneck" engineering today.
03-18-2013 09:01 PM
Northern Chevy On my 1995 pickup with the 350, lately I had reason to remove the rear quick disconnect fitting on the intake manifold and had read about there being a high possibility of twisting it off. Surprisingly it came out fine but did show some signs of possible lifting material inside although scraping a little inside seemed to bring it down to solid material so I don't know if it was a slight build up on the fitting or actual material lifting from the fitting. Of course being that it was out I wasn't going to take chances and replaced it with the Dorman unit in both the water pump and the manifold. As you can guess, I never had the proper tool and damaged the plastic tabs a little with other means of moving them apart for line removal and that was my own fault for not seeking out the right tool for the job.

The reason for my comment, back when I bought my truck new they were not factory filling this model with Dexcool but were by the next year and so soon on in my trucks life I actually switched from the green coolant to a Dexcool "compatible" coolant which is orange in color rather then the trademark pink. Through the years I would drain it and refill with fresh Dexcool compatible coolant and sometimes three years and up to five years between changes. Knock on wood, I've never had a rad issue and when removing the intake it appeared relatively clean in the head coolant ports and spotless in the intake side and any time I have changed the thermostat its always looked 100 % spotless in that area of ether the intake or the aluminum thermostat housing. So I can't say I used "Dexcool" but it was the compatible equivalent with similar chemistry and I don't know if that fitting in the intake is a good example but I haven't had reason to think its been a bad coolant for my engine at least. I do make sure I mix it with distilled water rather then anything questionable and never have anyone else working on the cooling system and adding the wrong/non compatible coolant as I expect that could cause all sorts of issues then.

I've had a lot more problems with the older green type of coolant { we can't get green coolant here now, its dyed purple } with slime build up issues or degrading of aluminum parts such as the thermostat housings etc. Also inside the overflow tank it stays clean unlike some of the older trucks we have which look like a sewer inside, those trucks typically have a copper rad and that may be some of the issue .. not sure.
03-18-2013 03:36 PM
MouseFink The quick disconnect heater hose fitting fitting if for the metal heater hose ends. The OE fitting contains a plastic clip with a restriction that diverts coolant from the heater to the radiator and better cools the engine. Use it. Any coolant not passing through the radiator is not cooling the engine.

Dorman 800-401.1 is the only aftermarket source for those fittings. Removal of the fitting is unnecessary and does not risk pulling the threads out of the aluminum intake manifold. You can remove the quick connect clip with the metal hose end using the proper tool. . A new clip is Dorman 800-405. Useed with a Dorman 800-408 quick disconnect removal tool.
03-18-2013 11:42 AM
Hogg
Quote:
Originally Posted by 1great40 View Post
I have had 2 long term experiences with Dexcool. The first is my 1996 Jimmy with 165K on it. Had been flushed many years ago (about 100K ago) and replaced with green stuff. Engine was perfectly clean inside cooling system. Engine had been opened once since because of a bad intake manifold gasket, original coolant re-installed. The 2nd one was my 2000 Sierra 4.8.. Water pump went at a little over 200K. The inside of that cooling system was as clean and the coolant was as clear as the day it went in 11 years before. I don't believe Dexcool to be a problem coolant and as stated the chemical design is also used in other coolants as well. The biggest problem you can have with coolant is opening the system up every year or so and messing with it. I know I'll get flamed for this but in the 45 years I have been building and repairing cars. I have never changed coolant on anything unless it diddn't have any to begin with...if it comes out to do some work, it goes back in.

Another observation is the GM intake manifold gasket leakage problem, which is universally attributed to Dexcool. I have never had a GM/Dexcool intake manifold repair job on a GM V8, the V 6's on the other hand...I've done plenty of them. My impression is that there is a gasket material/ torque spec/ thermal cycling issue on the V6 engines, in essence it's a design problem, not a coolant problem.

Before you wet your pants over the Dexcool, just run the stuff and when you do change it, use one of the newer "universal" antifreeze/coolants that are compatible with any coolant if you're worried, then the next coolant change you can move to an old fashioned ethylene glycol coolant if you feel more confident using it.

My bet is the car will be long gone to that big swapmeet in the sky before you have a problem related to any coolant.
You dont do many 1996-2000 Vortec L30/305 or L31/350 intake manifold gaskets?
These trucks are the 1996-2002 GEN-1E Vortec engine design. The intake gaskets have a bad design, but as you state, Dexcool is often blamed.



These 96-99 4.3/305/350 fullsize trucks also have that cheap heater fitting that comes out of teh intake manifold and supplies the heater core with coolant. Its a Quick Connect fitting that is made of cheap pot metal and breaks off if you look at it wrong. Dorman makes a great replacement. But even better, simply cut off the QC fitting and screw a conventional brass or other material pipe threaded collant nipple into the intake manifold and use a gear clamp to hold the heater hose on. I notice better heater performance when this is done.


You 1999+ LR4 4.8 engine is a GEN 3 engine design, it is much better design.

peace
Hog
03-17-2013 08:40 PM
1great40 I have had 2 long term experiences with Dexcool. The first is my 1996 Jimmy with 165K on it. Had been flushed many years ago (about 100K ago) and replaced with green stuff. Engine was perfectly clean inside cooling system. Engine had been opened once since because of a bad intake manifold gasket, original coolant re-installed. The 2nd one was my 2000 Sierra 4.8.. Water pump went at a little over 200K. The inside of that cooling system was as clean and the coolant was as clear as the day it went in 11 years before. I don't believe Dexcool to be a problem coolant and as stated the chemical design is also used in other coolants as well. The biggest problem you can have with coolant is opening the system up every year or so and messing with it. I know I'll get flamed for this but in the 45 years I have been building and repairing cars. I have never changed coolant on anything unless it diddn't have any to begin with...if it comes out to do some work, it goes back in.

Another observation is the GM intake manifold gasket leakage problem, which is universally attributed to Dexcool. I have never had a GM/Dexcool intake manifold repair job on a GM V8, the V 6's on the other hand...I've done plenty of them. My impression is that there is a gasket material/ torque spec/ thermal cycling issue on the V6 engines, in essence it's a design problem, not a coolant problem.

Before you wet your pants over the Dexcool, just run the stuff and when you do change it, use one of the newer "universal" antifreeze/coolants that are compatible with any coolant if you're worried, then the next coolant change you can move to an old fashioned ethylene glycol coolant if you feel more confident using it.

My bet is the car will be long gone to that big swapmeet in the sky before you have a problem related to any coolant.
03-06-2013 06:32 PM
39 chev I just spent 32.00 for 2 gallons of dexcool.I put it in my T-bucket this afternoon,since I have a new aluminium radiator I thought I was doing the right thing. I hadn't heard of any problems until I read this post..I plan on running it,The engine hasn't been fired up yet but my thoughts are that there are millions of vehicles using it,and dexcool may be getting blamed for poor engineering or lack of maintainence.
03-06-2013 08:46 AM
Hogg Its a fine coolant so long as your system is sealed. Problems happen when oxygen gets involved.

If I just filled an engine, I wouldnt flush it out. Just run it and swap out in 5 years.

Dexcool gets blamed for intake gasjets all teh time, some if it justified, but in teh case of teh 1996-2002 Vortec 305/350 is teh hrrible intake gasket design and the way the intake bolts dont apply their forces perpendicular to teh gasket face, they put the head, teh gasket, and the intake manifold in a state of shear. PLUS the stock heads are iron and the intake is aluminum, everytime that engine ehats up and cools down, teh dissimilar expansion rates, in a state of shear, cause the gaskets to roll and break apart. Another case where GM has swapped out durability for ease/speed of install on teh assembly line.

peace
Hog
03-05-2013 10:26 PM
RatPin Well I hope I was able to get almost all of it out. What a mess of a job though since my radiator does not have a bottom drain plug. Drained it through the lower radiator hose, ran water through, closed it up, filled with water, drained out lower hose again, ran water through again, fill with green stuff. Fingers crossed.
02-16-2013 06:07 PM
MouseFink The Dex-crud is supposedly "long life" and is more "aluminum friendly" because it has no silicates. Both green and orange antifreeze use ethylene glycol as the antifreeze element but Dex-cool has no silicates and uses OAT (Organic Acid Technology) for corrosion protection.

After a period of time, silicates drop out of the coolant and attacks lead solder joints in radiators and plates aluminum radiators and heater cores. The more extensive use of aluminum parts in modern engines and cooling systems is why they claim the green stuff with silicates for corrosion protection needs to be changed every two years.

I replaced my 1991 leaking brass heater core with lead solder joints after 150,000 miles and the new replacement heater core was made of aluminum with aluminum solder joints.
02-15-2013 04:06 PM
RatPin
Quote:
Originally Posted by sbchevfreak View Post
Pulling the hose won't get all of it. You need to have it flushed, or pull the block drains out, and run water through until it runs clear, and then for 10 more minutes. Dexcool is junk, and is the subject of a class action lawsuit in regards to gasket failure.
Well I was hoping that since I have never ran the engine that the block would not be filled yet. In fact I never even topped off the radiator. I put in two gallons of the orange and still could not see collant at the top of my radiator filler neck.

I was thinking to pull that lower hose, drain the orange stuff, put the hose back on, fill with water, drain that water, fill with water and drain a second time then fill'er up with the green stuff. Hopefully that will be enough. I cant imagine it circulated too far without actually starting the engine.

Am I wrong?
02-15-2013 02:23 PM
sbchevfreak Pulling the hose won't get all of it. You need to have it flushed, or pull the block drains out, and run water through until it runs clear, and then for 10 more minutes. Dexcool is junk, and is the subject of a class action lawsuit in regards to gasket failure.
02-15-2013 12:43 PM
snakebit68
dexcool

Yes, but flush it out really good. I know it sucks but I've seen the damage that crap causes. It really does erode plastic and rubber seals and then they leak, and then it gets where it shouldn't be and then it will causes catastrophic engine failure. (Bearings).
02-15-2013 10:33 AM
RatPin So then since I have not started the engine I should just be able to drain it out of the lower hose and be done with it you think? Maybe put some water in the drain it again before going with the new stuff.
02-15-2013 08:36 AM
snakebit68
coolant

Dexcool eats gaskets and seals. I've done so many GM intake manifold gaskets because of that crap. I wouldn't recommend it to anyone. I flushed it out of my new Chevy 2500 hd on the day I bought it and replaced it with green.
02-15-2013 06:11 AM
MouseFink Only a chemical flush will get rid of Dex-cool if you want to use a ethylene glycol based coolant . A vehicle with a coolant recovery system should never use Dex-Cool because exposure to air will turn it into orange mud. Dex-cool uses OAT (Organic Acid Technology) instead of ethylene glycol silicates as rust inhibitors and just like any coolant, it should be changed every two years or every 20,000 miles, especially if it is Dex-cool.

After my 1991 S-10 Blazer 4x4 was purchased in the fall of 1991, I have used Prestone anti-freeze concentrate diluted with a gallon of distilled water and I replace it every two years. The 22 year old cooling system is like new. Since it was introduced in 2006, I have used one gallon of Prestone 50/50 Anti-freeze Coolant per car and I change it every two years or less. . It is a 50-50 mix of ethylene glycol coolant and demineralized water.

A 50/50 coolant is convenient to use but you are paying double the price for half the amount of ethylene glycol coolant. Just like any other product, people must pay extra for convenience.
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