1998 Oldsmobile 88 Intake Problems

baron1701 · #1 09-08-2008, 10:34 AM

Hello,
I have posted many times relating to my problems with the upper intake on my car. The car is on its second engine. I have replaced the upper intake 3 times in just a few months. I found the problem to be a missing stovepipe between the upper and lower intakes.

Should I be looking at selling this car soon? I may have fixed the problem for good but I am concerned about the possible damage to the bearings, ect.

Airjer_ · #2 09-08-2008, 10:47 AM

What happens when it fails?

How did you "fix" it the last time?

baron1701 · #3 09-08-2008, 10:58 AM

The plenum melts where the EGR gasses go through and causes the coolant to leak into the intake. I replaced the pipe ( EGR stovepipe ) and I think it should be ok. There was no metal pipe before. I dont know why. I have heard of these 'leaks' causing damage to the engine. My original engine in the car had been hydrolocked before and messed up a rod causing a knock. I havent been able to start my car yet after doing the intake, but its pretty badly flooded. I am going to work on it tonight.

Airjer_ · #4 09-08-2008, 11:27 AM

O.k. so you have the plastic plenum melting problem. Are you replacing them with new parts. The new plenums have been reinforced in this area to help solve this problem.

Anytime this happens the first thing to do is remove all the plugs as soon as you recognize the symptoms. Then make the repairs. Then turn the engine over be hand using a wrench or socket on the crank pulley bolt. Once you have turned it over buy hand several times you can then crank it over using the starter to help force the remainder of the coolant out of the cylinders. Its also not a bad time to replace the plugs since there all out anyways. its not a bad idea to change the oil as well incase any coolant made its way into the pan.

Put the plugs back in, re-inable the coil/injectors, and crank it over. It should start right away.

Trying to start withought removing the coolant first can cause damage to the engine not to mention break off the nose cone on the starter, which does happen on occassion.

Replace the plenum with a new updated plenum, remove the plugs to get the coolant out of the cylinders, make the repairs, and change the oil to get rid of any coolant that may have made its way past the rings and into the oil pan. You should be set.

baron1701 · #5 09-08-2008, 11:36 AM

I bought the original upper intake Plenum from the Junkyard because I was short on time and cash. The plenum is under waranty so I have not had to pay for the last several units. I will replace the plenum ASAP with a new unit, just waiting for the extra cash. My other car (2002) Oldsmobile Alero had brakes and wheel bearings replaced by me last week so I am quite broke. If I need to I can sit on the Olds 88/LS but if I can clear it out tonight I want to start running oil through it. I have about 20 quarts of oil that is used but very clean. I plan on doing 2 or 3 oil changes with this oil and some flush within a week or two.

*I did notice when I checked the dipstick that there was sludge on the bottom. This is the first time I have had this problem so I am dumping the oil ASAP.

BNaylor · #6 09-08-2008, 12:14 PM

3 UIM plenums in just a few months? Resolving these type issues with inadequate funds can be a problem due to the shortcutting.

Do you have any sludge in the coolant reservoir? How about at the radiator filler neck and on the back of the radiator cap? On the subsequent UIM plenum replacements did you physically see any damage or melting at the coolant passages at the point where the throttle body connects to the UIM and on the two coolant ports from the LIM to the UIM? Any significant amount of coolant sitting on the top of the LIM after the UIM was removed?

The LIM gaskets are an issue just as much as the UIM plenum to include UIM gasket. Technically both should be replaced at the same time. Plus it doesn't make sense not to use the revised UIM plenum on a '95-' 98 GM car with the SII 3800 engine either the GM/Delco or aftermarket brands like Dorman or APN. Also, they come with the smaller diameter EGR stovepipe. However, it won't help to throw on any more UIMs if that is not your issue.

Airjer_ · #7 09-08-2008, 12:34 PM

For under $10 you can buy 5 quarts of new oil. You would be way better off!

I'm all for a lot of things used but oil is definitely not on my list!!!

baron1701 · #8 09-09-2008, 07:44 AM

The upper intake plenums that I removed were severely melted. The plastic where the EGR hole is located was badly damaged. Without the EGR metal pipe protecting the plastic I realize that it is a miracle they survived as long as they did.

I stress that it wasn't until I pulled an intake from another car that I saw the little pipe there. The engine was replaced 6 months ago and I have been working the car over since. The plenum problems have been caused by this missing pipe. The engine didn't come with one and I have to assume that the intake was done shortly before I got the engine and the pipe not replaced.

I managed to get the car running very well last night and flushed the oil with K & W oil flush and (2) 5 quart oild changes with my used oil. I replaced the filter and oil. This weekend after I get a hundred or so miles on it I am flushing again and replacing with the Semi-Synthetic I usually use.

This last plenum failure actually very nearly hydrolocked the engine. I started running out of power and dragging a cylinder (at least thats what it felt like) before I parked it. The other intakes I caught a lot earlier due to losing a small amount of coolant every day. The lower intake was flooded so bad that when I pulled the plenum it leaked over.

BNaylor · #9 09-09-2008, 07:59 AM

Obviously hydrolock will be the result. On the EGR stovepipe did you install the stock or a modified one. As soon as funds permit I recommend getting the revised UIMs either GM or aftermarket, preferably the APN or Dorman aftermarket. For GM UIM plenum any '99 and up GM car with the SII 3800 has the revised UIM and smaller diameter stovepipe if you decide to get another pull from a salvage yard.

Also, be sure to monitor for any further coolant loss once you get it running to your satisfaction and monitor for any possible sludge in the cooling system. Good luck and let know how it turns out.

Airjer_ · #10 09-09-2008, 08:17 AM

If you put the pipe in this time than maybe you will get a little more life out of it. I Don't think I have ever had one that wasn't completely locked up so you really got lucky this time.

baron1701 · #11 09-09-2008, 10:59 AM

I was less than a mile from the house on the way back from work ( about 35 minute drive ) when it had trouble going up a hill. I kept it going untill I pulled over and shut it right off. I can imagine if it happened on the highway only 5 minutes earlier.

I think the EGR tube I used was stock. I will be on the lookout for an updated upper intake if I have any issues this time. Next time I think I will buy a new one and get the 'Reinforced" version that I have seen. For the next week or two I will be keeping an eye on the oil and coolant to see how the gasket is sitting.

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