Hello- I bought this 1998 Oldsmobile Eighty Eight LS in August. Was not able to see it in person or test drive before I bought it. Shipping company met me at an exit off the thruway and I drove the car home. First thing I noticed was that the coolant reservoir was empty and bone dry. I filled it with the recommended coolant but noticed that the level continued to drop. Also filled at the radiator, but coolant level would drop after driving even a short distance and seemed to be continuing to drop even when the car was sitting. After filling it to the fill line a few times, only to see it continue to disappear, I started checking for coolant leaks but could not find anything anywhere. Nothing on the ground underneath the car, nothing when I checked the rubber hoses from coolant reservoir to radiator. Then I read about the common issue that could be causing it to leak into the engine via the problematic plastic upper intake manifold. It was emitting a noticeable about of visible white exhaust when running. So I stopped driving it and it has been sitting for three months. During that time I started noticing what looked like oil in rain puddles near the car after every hard rain. I had noticed no oil leaks during at least the first week or two when I was checking for coolant leaking. But now the plastic cover underneath the engine and other places in that area clearly have oil residue on them and there was a single small drop that had not fallen to the ground yet, so it is leaking oil from somewhere. One of the main reasons for buying the car was so that I could start learning how to do my own maintenance. Any advice on where to begin would be appreciated. I was planning to attempt the intake manifold replacement in the spring. Not sure if there is a way to verify first that's where the coolant is going, though. And now with the oil leak I'm wondering if I should tackle that first. I read that it could be a bad oil pressure sensor. But also not sure how to verify if that is the cause of the oil leak. The car is completely rust free and has just under 78,700 miles. Battery has died twice, first time I think because I left an interior light on and the second time I think was just from sitting for so long these last few months. First photo is just after I got it. Second photo is where the coolant level has dropped to in the reservoir from when it was full and has just been sitting. Third photo is the exhaust as it was running today.

 

I replaced the oil pan gasket on my 96 98. It's easy since the engine is transverse mounted. There is a sensor in the side of the oil pan that has to be disconnected to drop the pan.

The upper intake manifold on the Series II 3.8l is pretty straight forward to replace. Make sure you have a torque wrench to tighten the fasteners. I drove my 96 over 50k miles and never had to replace the lower intake manifold gasket. The sparkplugs are easy to get to in the back with the upper intake manifold off.

You need to do a coolant flush if your going to replace the upper intake manifold. Only use Dexcool. It does NOT mix with green coolant. When Dexcool gets old it congeals and can cause the engine to overheat and the head gasket to blow.

When you do the coolant flush there are elbows going to the heater core that need to be replaced. The OE elbows are plastic and have a valve in them that fails. Just replace them with the metal heater core elbows that don't have a valve.

Before doing the intake manifold you can rent a coolant pressure tester from the auto parts store and find the leak with the engine off.

 

Wonderful...

Here's to hoping it was just really low on antifreeze. She takes almost 3.5 gallons, maybe it was down to 1... But with rampant white smoke in August it doesn't speak to condensation. And if the exhaust smells sweet it's a wrap... What I will add is a close friend also has a 10th generation and he swears by it. Has been prodding me to get one for years. Meaning the car is likely well worth your efforts to get her back up to speed. Especially because the rest of the condition seems to be solid.

 

Thanks, I just ordered a coolant pressure tester that Advance Auto confirmed will fit the 1998 eighty eight. When I got the car and realized there was no coolant I got the recommended Dexcool specifically but previous owner had been using the green coolant since I could see dried up green particles from it in the bottom of the reservoir. I wonder if that is part of the problem? I did not know they could not be mixed. The Dexcool I put in is fresh obviously, but no idea how long they had been using green coolant or for how long the reservoir had been empty, just they it was completely empty and dry when I got the car. Coolant level has definitely been dropping even while just sitting since then so maybe there is a small leak somewhere else before it is getting into the engine. But with the persistent white smoke out the exhaust it must also be leaking into engine as well. Will get a torque wrench to do the upper intake manifold replacement. Didn't know about the plastic elbows that also need to be replaced. Will try to get some photos of the oil leak to see if I can confirm where it is coming from.

 

I have not noticed any other major problems during the relatively short drives I have taken it on. These were rural roads and highways, have not had it in stop and go traffic yet. Engine temp was good, hasn't overheated or set off any warnings. Cruise control worked the first time I used it and then would not engage again after I had clicked it off and tried to set it again. I drove a 1994 Eighty Eight Royale as one of my first cars. Had been purchased new by my grandparents originally. Unfortunately I totalled it in an accident on the highway after I had been driving it for only about 3 years. I would say the '94 was probably superior to the '98 model year in my opinion. The '94 never leaked oil or coolant and had very few if any problems over the 15 or 16 plus years it was driven by our family. The road salt used here in the northeast will rot them out from the underside though.

 

The coolant elbows you want are Dorman 47065HP. Green coolant should only be used in place of Dexcool if the engine is rebuilt and hot tanked. Since you're probably just trying to get it on the road reliably I'd flush the cooling system thoroughly with a flush kit available at your local auto parts store.

https://www.oreillyauto.com/detail/c...kit/prs0/afkit

I never got to do the repair on my 96 before the 4T65E died, but be aware that the subframe mounts are known to rust and rot out up north. It can be repaired, but is an engine out repair.

BTW, she's a beautiful machine! I bet that 94 was a looker too with the faux fender skirts.

 

Well what a coincidence, I'm fairly certain my friend's is a 1994.

Sorry that the your 1998 is so disappointing, she looks great. Appearances can be deceptive. And she was born with so much more power than a 1994...

 

Both the intake manifold gaskets, and the intake manifold itself are problematic on that car. If that was my car, I wouldn't start that car again before replacing the manifold. Also, I certainly wouldn't be pressurizing the cooling system for fear of hydrolocking the engine. If you do try to start it, and it doesn't want to crank, take the plugs out and crank it as it likely has a cylinder full of coolant.

 

Skip Dexcool and get something like the 15 year Prestone, compatible with all coolant. I have seen regular green mixed with Dexcool, literally turns into clay.
Plastic intakes are common these days. Early ones with the added terribleness of Dexcool made for a disaster. Get a new intake and Premium gaskets. Good luck.

 

I suppose a universal coolant would work. Just make sure it's not green coolant. When I did the tune up and coolant flush on my 96 98 I didn't have to worry about the Dexcool until I swapped the radiator during that 50k miles.