I'm curious as to when people had to replace the lower intake manifold gaskets (age of motor and mileage).

Have any of you replaced it while doing other maintenance and once you saw its condition you were glad you did?

What type of coolant were you using? Dexcool? Traditional green stuff?

I've learned this is a weak point in the engine design which can allow coolant to drain through the lifter valley and into the oil pan, let alone causing inevitable overheating problems.

I'd appreciate getting a handle on when these gaskets start leaking at the water passages.

For my Blazer:

• 18 y.o. with 135k miles. No hint of an issue with it, yet!
• I have used Dexcool except for a few years after when the local Jiffy lube didn't do a good flush and put in the green stuff creating a bunch of sludge that I didn't learn about until I started to have cooling problems. Went back to Dexcool.

Thanks,

Christine

 

05 Jimmy , 206000 KM (123 k) .Haven't had to do them yet.
02 Astro 160000 KM (96 k) . Haven't had to do them yet

 

1998 w/ 87,xxx
1999 w/ 122,xxx

Neither gave hint of a problem, both had gaskets that were toast.

 

02- 208,000- dex.
There were hints and allegations beforehand.

 

'02-180,000-green stuff. First sign noisy lifters at start up then coolant smell then increasing oil level then chocolate milk color.

George

 

In my former '02 in 2011 at around 70,000. An oil analysis showed traces of coolant in the oil, so I decided not to wait for trouble to find me. I had the gaskets replaced with the correct Fel-Pro set.

 

I used 2 bottles of super flush, the capacity of my system was just over the amount covered by one bottle. My 2000 had 120 K and brown, lumpy gravy looking dex cool and a clogged heater core. After repeated flushing with water I filled it back up with prestone all makes. 3 years later it's the same clear yellow and mixes with both if necessary. My personal coolant mix is 2 gallons concentrate to 1 gallon of distilled water. That puts it at 66% , under the 70% max for best performance and it gives me the ability to just add more water if it gets low.

I'm at 126 K miles on my original LIM gasket and it's a concern for me. By spring I'll be around 130 K and I'll change it. The number of miles in my head that I don't want to take it past is 150 K. As rriddle mentioned, Fel-Pro # MS98002T is a steel upgrade that's the only one to use considering the labor and importance of the gasket. I recommend replacing yours because you tow with your blazer and because you're thinking about it.

 

Yeah, I'm now thinking I'll do the LIM gaskets next spring. I've heard of the better Felpro gaskets too. So far no hint of water in my oil. If it does go, I sure hope I get a little warning instead of a catastrophic failure.

Christine

P.S. Please keep the information coming. I think this could be the making of a useful thread for people to reference in the future.

 

1999 Blazer
135,000 miles

Dexcool until it was mixed with the green stuff. Later did major flush. Not much sludge at all. Will likely do another flush anyway.

replaced LIM gasket on 10-2017. Looked good with no visible deterioration.

 

1996 342,000 miles green stuff since i have owned it. No milky stuff in the oil. Never replaced the gaskets. But i will be soon as i think i have a vacuum leak along the outside edge thats causing my blend door issues. But no overheating and no antifreeze in the oil.