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Discussion Starter · #1 ·
Hi everybody,
Sadly I have to ask our help again. A few days ago I noticed that the check gauges light popped up. Later on it got constant when the car was hot and idling, and realized the oil pressure gauge felt into the red mark. I bought a mechanical oil pressure gauge and hooked it up to the car. I was hoping the oil pressure sender unit is the faulty, especially, because when I took it off, there was oil at the connector. the reading was okay when the engine was cold, above 50 psi, it dropped to 20 psi at warm, and stabilized at 9 psi when it was hot (IDLE). As I know it is too low. It was following the acceleration, but when I tested I found out there is blue smoke coming from the exhaust when I increased the RPM. This site (http://www.aa1car.com/library/problem_engine_smoke.htm) says, the worn valve guide seals or guides, cylinder or piston ring can cause it. Next step will be a compression test.
I had a valve job on both cylinder head like a year ago, maybe the guide and/or seals will be the faulty this time.

Any suggestion?
Thanks
 

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The oil in the exhaust can be any of the things you mentioned in your post. But the drop in oil pressure is do to main, rod and cam bearing wear. This increases the clearance of the rotating parts and lowers the oil pressure.

As the oil gets hotter, it also gets thinner. That is why pressure is better when cold and will drop into the red zone when idling with hot oil.

I see a rebuild in your future. How many miles are on the engine?

If you replace the main and rod bearings before significant wear occurs to crankshaft, you will be able to save the expense of a new crank.
 

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Ramblin' Wreck
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What weight oil are you using? How long ago was the last change? Get the oil changed and immediately check the pressure with the engine hot to eliminate the possibility of any oil dilution/contamination. If no change, I'm afraid Robert is right.
 

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I put a 10w 40 high mileage oil in it. It almost due for an oil change now. Could the oil change fix the smoke in the exhaust? If I have to change the bearings, do I have to take out the whole engine?
Oh and it has about 130k
 

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It's easier to change the main bearings with the engine out of the car, but I've seen people do the job with engine in place. I would remove the engine for bearing replacement.
 

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Discussion Starter · #6 ·
Sorry for the late response. So I decided, that I will make a big engine rebuild in my garage. Means I purchased an engine hoist, and I will take it out from the car. I want to change every part, sealants and gasket that could cause the problem right now, and want to eliminate the possibility to have something similar in the future. My question: what should I change beside the main and rod bearings?
 

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First thing to do is download the 98 service manual available in 4th gen tech section. It will have complete specs on all internal parts. You need to make measurements of things like cylinder walls. You first measure at bottom of cylinder, which is the unworn part. Then measure the cylinder at several places where rings wear cylinder.

You compare measurements of unworn part to worn part. There are specs in manual that tell you weather you need to bore engine and get over sized pistons. Or if a honing and new rings are needed.

You will be doing measurements on crank, cam, connecting rods and all other wear points of engine. Service manual will tell you what to check and what the wear limits are for each part.

This is just the beginning. Even new parts will have to be measured to see if they are within spec. You might want to try to find a rebuilding book on the 3.8 v-6. If available, it will help give you an idea of what is involved.

Anyway, the point I'm trying to make is, rebuilding an engine is not just buying parts and throwing them in. It involves many tasks which need specialized quality measuring tools, special service tool and the knowledge to use them. And perform the tasks that are involved.
 

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Discussion Starter · #8 ·
Sorry for the late reply, I had lot of things to do. When I said I will rebuild the engine I meant to do everything I can. As I know the engine was rebuilt not long ago before I bought the car, and I already did a valve job on both cylinder head.
I tested the compression and I got the following result: 148 148 145 155 149 and 165 PSI. The 165 looks a bit much tho, but I don't think that would cause the low oil pressure.
So the plan is still to change the main and rod bearings. What else should I consider to change/fix?
Thanks
 
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