Hello,

My 1997 Olds Bravada is getting a bit tired with its 155K miles, and the 17MPG average is mediocre at best. I'm selling my Bravada this weekend and I've been looking at some cars for sale in my area.

I've come across a gold 1998 Oldsmobile Regency with the Series II L36 engine. The car has 74,000 original miles and is a 1-owner. The owner'* husband apparently owns 3 service stations, and has all the service documents if I request them. $1899 takes it.

Now, I've been reading around, and this intake manifold issue is scaring me... Coolant in the oil, uhh! I've heard this is not an if problem, but a when problem... Am I safe from the failure with a car with this low mileage or model year?

What commonly happens? Does the lower intake manifold gasket go, or is it just the upper intake manifold gasket? What about the intake manifold itself? I've also heard about the EGR playing a part in this gasket failure, too... Is this a preventive maintenance kind of repair? I'm fairly comfortable doing it, especially with AllData at my side, but, being the poor college kid I am, I don't wanna have to sink any more money than I have to right after buying the car...

Any advice on this would greatly be appreciated.

Thanks,
Nick

Lot'* of good questions Nick.

Here'* what happens on the L36 and why it happens. The upper intake manifold fails due to EGR gasses and many engine cycles causing the upper manifold to get brittle and crack. The upper manifold is the problem area, not any of the gaskets.

In the upper manifold are two small runs where coolant is brought to and from the throttle body. These two runs flank the EGR hole in the manifold. Before 2000ish the size of the metal tube coming up out of the lower manifold into this EGR hole was rather large. This didn't allow much air gap for cooling from the hot tube with EGR gasses in it to the plastic based upper manifold. As enough heating and cooling cycles occur the plastic manifold cracks in the EGR tube area. This wouldn't be a problem if there wasn't a pressurized cooling run to the TB on the other side of that cracking area in the manifold. When the manifold cracks, the coolant fills the lower manifold and then begins running into the cylinders and being burned. If the crack is large enough, some cylinders fill and the motor hydrolocks. This is all easy enough to fix by putting a new aftermarket manfold on the motor.

While changing the upper manifold, the lower intake manifold gaskets are usually bad and should be replaced at the same time with dealership alumimum gaskets.

Doing these two repairs or doing the LIM gaskets and plugging the coolant flow to the TB though the upper manifold, you will have prepped the motor to run forever.

What happens is the EGR tube gets hot, and cracks the plastic UIM. Check the maintenance records and see if that has been taken care of. Generally with those miles it should be OK for a while, but will still need to be taken care of. If your good with a wrench, it can be done in a few hours and for $100 or so.

Thanks for the informative replies! I was under the impression that the Dexcool also played a part in the process, but I was only assuming because that was the problem with my Bravada and other 4.3L V6 powered trucks. The Dex-cool would mix with air from low coolant levels or leaks in the system which would sludge up the coolant (which didn't have any corrosion inhibitors) and eat away at the lower intake manifold gasket causing leaks.

My father had a 1992 Park Avenue (non-Ultra) when I was a kid. I didn't remember any kind of engine problems AT ALL with that car, and that was why I was looking into a 3800-powered car (the fantastic MPG also played a part in it too...). Were these older 3800'* affected?

Thanks,
Nick

EDIT: Also, would blocking off the coolant passages to the TB cause adverse effects during the winter time? How do you block off these passages?

The 9(1-2) to 95 engines, the L27s, did not have this problem to such an extent but could still have a lower intake manifold problem. Danthurs has taken apart the failing lower intake manifold gaskets to some extent, and he'* shown that weak spots fail and cause the gaskets to come apart. I don't think anyone has found conclusively that the Dexcool eats away at gaskets, just that the LIM gaskets structure is faulty. The LIM gaskets are made out of the same stuff that makes up the UIM gasket and the UIM itself. They seem unaffected by coolant flow except for the whole cracking thing.

Blocking off the TB passages doesn't have any adverse effects. It'* basically for emissions so you get less dense air, from what I understand. To block them off, plug the LIM'* TB coolant passages and then open up the bypass, the part that sits under the throttle body under a little plate that looks like a turned-over tent.

Great info! I'll be checking the car out tomorrow afternoon (after the hour and a half drive there). If I get it (which I think I will) this is surely the right place to discuss it.

Thanks,
Nick

Sure thing. Good luck!

Well, I bought the car! My lowest mileage car @ 76K miles

And here, on the first day of owning it, I locked myself out... The PO didn't give me the door/trunk key or remote (which I didn't even realize) and I locked the door when I got out of the car at college... After class, I tried inserting the ignition key in the door and it wouldn't fit... Uh Oh. 30 minutes later and AAA arrived to rescue me. I'm going to have him mail me the key or remote if he has them.

I did notice (which I didn't notice when I test drove the car) a shudder from the tranny when 4th gear engages. (Just around 50-50MPH) Also, it happened during the 2-3 shift with moderate throttle going uphill. Research has revealed that the most likely cause is the ignition system. A bad coil pack, plug or wire is the most common culprit. If I step on the gas more, it'll pick right up and continue to accelerate. I'm thinking its just a power-under-load type of issue.

Finally, the driver'* side HVAC mix door is stuck in the COLD position. The passenger'* side gets nice and toasty, but the driver'* side stays cold. I'll have to manually keep it stuck open and unplug the motor until I can get in there and replace it.

Any comments on any of these issues?

Nick

EDIT: I just took the dash kick panel down to check things out. I played a bit with the linkages and now the mixers work fine. yes!

For the shudder, I'd look at the transmission fluid, perhaps change the filter, and then you should also check the ohms of the ignition coils. Let us know how it goes!

I asked the owner to put the car on the lift when I went to check it out. While checking the undercarriage, suspension components, brake/fuel lines, etc, I noticed how conveniently located the Tranny pan and Oil pan are.

I'm getting a *tiny* bit of seeping from the oil pan gasket, and looking at it, it seems like quite an easy task to change. Nothing in the way! The same thing is for the tranny pan.

I think a nice fresh filter, gasket and some Dexron-VI wouldn't hurt at all. Also, an oil change, spark plugs and wires are on the list too... I want to be sure I have an accurate starting point for fluid change intervals...

EDIT: I also recorded each cylinders CURRENT misfire and HISTORY misfire numbers. I didn't know how to decipher the numbers, though. There were numbers in the 30K range!

Thanks,
Nick