antifreeze eating intake gaskets

[Hooked_on_HP]

I have a 98 Chevy dually with a 7.4L vortec engine. I developed an antifreeze leak into the oil. I took the intake off and discovered the rubber in the gaskets arround the cooling passages where the intake mates with the head was deteriated.These gaskets have like a rubber O ring arround every passage. I went to my locale parts store and got the new gaskets ($59.for the lower). The parts guy who I know well told me there have been a lot of problems with the Dexcool antifreeze causing this. Has any one else heard of this? Should I go back to green?
Bill

 

[kenmac]

I have also heard and read this about dexcool. I don't use it

 

[Diamondpilot]

Yes, its a common issue. Go the the Corvette forums and do some reading. Something about the DexCool and Aluminum engines. Not sure if your 7.4 is DexCool or not but now days the Dmax guys recommend you change the coolant every 50,000 miles. By the way I know a guy with a Dmax that had this happen too but GM swore it was a head issue and tried to blame it on him. We have went through this a few times on my dads and uncles Vette's the last being last summer on my dads.

My only suggestion is change it and be ready for it to happen again. Short of getting rid of the truck the only thing you can do with a DexCool equipped engine is change the coolant every 50,000 or less to help prolong them.

We also see problems in the 5.0 5.7 6.2 and 8.1 marine engines with DexCool. I switch them out to the old Green stuff personally but this is on the few engines we see with closed cooling systems. Most marine engines around here are sea water cooled, or lake cooled in our case.

Chris

 

[Hooked_on_HP]

Is it DexCool only causing the problem or all red antifreeze. maybe it is just a coincidence but I had just changed the antifreeze about a month ago when I changed the thermostat.
Bill

 

[carpenter383]

I've heard of dexcool doing this sort of thing too, don't know if it's true. Most say flush the deathcool and refil with green. The 2 don't mix, so flush completely.
The worst intake gasket probs on gm would probably be the late 90's 3.1 and 3.4 v-6's. Gm used a plastic intake gasket, and they fail as soon as 40,000 mi.
Check for water in your oil, look at the bottom of the oil cap and see if it's milky.

 

[DIRTROAD]

Could you not try adding a diesel coolant additive (DCA) to your system. If if will keep the sleeves in a big diesel from pitting, surely it would solve your problems.

Also checking the PH is very important.

 

[Diamondpilot]

I've heard of dexcool doing this sort of thing too, don't know if it's true. Most say flush the deathcool and refil with green. The 2 don't mix, so flush completely.
The worst intake gasket probs on gm would probably be the late 90's 3.1 and 3.4 v-6's. Gm used a plastic intake gasket, and they fail as soon as 40,000 mi.
Check for water in your oil, look at the bottom of the oil cap and see if it's milky.

Was that 3.4L engine in the Pontiac Transport Mini Van? If it was everyone I knew who had one of them had issues. If I remember it was not to bad of a fix, maybe $800??? Because of the issues and they flooded the market with them on cheap leases the value fell like a rock. All in all it was a good motor but noting like the 3.8 GM put in everything. That motor is legendary for durability.

My neighbor's wife had one that had the intake issue and at like 30,000 miles. They got it fixed and tried to trade it and were taking a bath so sold it outright for something like $6500 after just 3 years of ownership. They replaced it with a new Honda Oddesy and later a Lincoln Aviator which they still have.


Chris

 

[carpenter383]

Was that 3.4L engine in the Pontiac Transport Mini Van? If it was everyone I knew who had one of them had issues. If I remember it was not to bad of a fix, maybe $800??? Because of the issues and they flooded the market with them on cheap leases the value fell like a rock. All in all it was a good motor but noting like the 3.8 GM put in everything. That motor is legendary for durability.

My neighbor's wife had one that had the intake issue and at like 30,000 miles. They got it fixed and tried to trade it and were taking a bath so sold it outright for something like $6500 after just 3 years of ownership. They replaced it with a new Honda Oddesy and later a Lincoln Aviator which they still have.


Chris

Yup 3.1's and 3.4's in ALL '96 to 2002ish? gm vehicles. Fel pro sells a metal replacment gasket set for like 85 bucks, it comes with valve cover, intake, egr valve gasket, and even a new oil pump drive o-ring (where the distributor used to be). It's the only way to go for a permanent fix.
Lifter noise is the other issue, spray some carb cleaner in the lifters (while you have the intake off) and replace the oil with rottella t and it should be quiet as a kitten.
I just did a 3.1 intake gasket change in a '98 cutlass, took about 4 hrs. so 800 bucks is kinda steep for this job ( maybe not in a minivan though) I charged $375 for the whole nine yards You're right about the 3.8's being good engines, so are the 3.1's and 3.4's overall.

 

[carpenter383]

hooked on hp, see if they sell a fel pro "perma-seal" intake gasket for your 454

 

[mjncad]

Weren't the 3.1 and 3.4 GM engines nothing more than bored out 2.8's? The 2.8 V6 was a crap engine with no durability, so I just shook my head when I heard GM bored them out for more displacement.