Was the intake manifold or gasket failure problem eliminated in later years like 99.

Am looking at a 99 Olds LS

Unfortunately not. Still a possible problem if I'm not mistaken. They do however make reinforced upper intake replacements for the L36 that are better than the original. Can't remember the name of the company I'm thinking of though

Dorman. That'* the new one, but it'* identical to the new GM intake. There'* also some aftermarket 'fixit' kits available now. Do it yourself without replacing the whole intake.

I haven't heard of a 99 fail yet, so it may be updated. There'* some controversy around this.

99 Bonneville have the least amount of failures and that'* the yera they finally fix the bugs from the other 10 years of the same generation.

I am starting on my 99 tonight as a matter of fact! I've got some seapage between the upper and lower in the EGR port area. I'm replacing my upper intake with a used GM intake that only had 20K on it, replacing the lower gaskets, installing an aftermarket stove pipe between the upper and lower (available here: http://www.ken-co.com/manifold/default.htm), 180* stat, and a Stant lev-r-vent radiator cap. Another user on this forum, 57chevythunder, also had the upper intake in his 99 cut loose at 90K miles.

Why are you changing to that radiator cap?

If your orange coolant is original I would change it too.
It doesn't last half as long as the 100k it claims.

Yes, I'm going to flush the coolant as well once I'm done with the replacement.

The spring load Stant cap maintains pressure more consistantly than the OEM cap. With the DexCool system being sensitive to air pressure, it'* best to use a spring loaded radiator cap.

Hi

If air is present in a Dex system, corrosion begins because Dex doesnt "plate" the surfaces with silicates as green does, but rather needs to be in constant contact with all surfaces to provide its anti corrosive benefits.

Green uses the plating method, which works quite well regardless of air. The only drawback, as the anti corrosion additive package has a shorter life span than does the OAT Dex type coolants....and consequently needs to be replaced about every 3 years.

I dont think that Dex by itself, plays any part in the upper failures we have seen, but that corrosion and the sludge it becomes, if left untreated, may cause many other terrible problems.

If you must stick with Dex or any OAT coolant, flush it every 2-3 yrs, and for pete'* sake, replace the OEM radiator cap with a aftermarket one such as Stant. Also, make sure that your coolant recovery bottle never, never, ever, is empty which will allow air into the system. Maintain that coolant level as though it was your life'* calling.

However, if you observes reddish corrosion on the inside of your existing cap.....flush teh system completely and thoroughly..

If I was to have stuck with a "long life" coolant....... I would have chosen Zerex which provides excellent protection without some of the other brands'* known "issues".


an interesting read on OAT type coolants and issues owners are faced with.

http://www.coolprofits.com/articles/...ohnbrunner.htm

http://www.motor.com/MAGAZINE/Pdf/082002_04.pdf