Intake Manifold Oil Leak / Vacume Leak

[Mark96CE]

My 1996 LT1 CE has been leaking a good amount of oil. I have been looking for vacume leaks since I failed smog and pulled 6 codes most are o2 sensor codes. I dont believe they could all be failing I am steal learning. The car intermintantly runs ruff. I removed the egr valve and noticed dirt / oil at the bottom of the intake and was wondering if it is leaking oil there could that cause a vacume leak that would be giving me these other problems. How much of a job is it for me to fix the leak?

Thanks

Mark...

 

[JAKE]

My 1996 LT1 CE has been leaking a good amount of oil. I have been looking for vacume leaks since I failed smog and pulled 6 codes most are o2 sensor codes. I dont believe they could all be failing I am steal learning. The car intermintantly runs ruff. I removed the egr valve and noticed dirt / oil at the bottom of the intake and was wondering if it is leaking oil there could that cause a vacume leak that would be giving me these other problems. How much of a job is it for me to fix the leak?

Thanks

Mark...

First thing is to identify the point of the oil leak . There are several different ways to do this. One is to completely clean all the areas where oil is present. A spray carb cleaner, etc., is good for that; I've use it before. Then buy a bottle of leak detector and add it to the engine oil. Run the engine for a while and where ever the leak is, the additive will point it out.

Pulling the intake to change the gaskets isn't hard at all on the 96 LT1; MAy take about an hour. I pulled mine a couple of days ago to change the oil drive gear to MSD version (part # 8561).

I always dimple the China Walls and the corresponding areas on the underside of the intake with a nail-set and use Sensor-Safe Silicone Sealant on the China Walls. The dimples provide something for the sealant to "bite" into.

I use a thin leayer of SSS on both sides of then intake gaskets and follow GM'S recommended torque sequence and I torque the bolts to 35#, going over and over them until that torque reading takes a set.

SSS pretty much eliminates any chance of a vacuum leak. Just don't use so much that it'll push over into the intake ports to disrupt airflow into the heads. A THIN layer is all that's needed.

Even though pulling and re-installing the intake manifold isn't very difficult I figure "Why have to do it AGAIN!"

Jake

 

[Mark96CE]

Thanks Jake, I will start by finding the oil leak as You suggested. This is my daily Driver and I dont have another vehicle. Any more good advice to quickly solve my smog problem would be appreciated... (I live in CA)...

Mark...

 

[JAKE]

Thanks Jake, I will start by finding the oil leak as You suggested. This is my daily Driver and I dont have another vehicle. Any more good advice to quickly solve my smog problem would be appreciated... (I live in CA)...

Mark...

Well, Mark, in order to pass Smog, everything has to be working as it should. Any vacuum leak or oil entering the intake track will throw off the emissions readings. So the engine has to be buttoned up tight.

Since our engines are so sensitive, all the sensors have to be working properly. You can have AutoZone, or some other store, check for any stored codes. If any are found, they must be corrected.

Not sure how CA works, but some states offer a sort of "practice test" session just to see if everything's up to snuff before having the actual test run. If CA offers that, I recommend it.

Any out of spec readings can then be addressed based on what could cause them.

What ever you find, post it here and we'll do what we can to help out.

Jake

 

[topless82vette]

what were your failed readings at?

 

[Mark96CE]

I should not have had it tested the check enging light was on it put out allot of codes. Not sure where the test papers are but it is now a gross polluter. I now only have till the 30th to fix it.

Mark...

 

[JAKE]

Oil or even a vacuum leak can cause the 02s to set a code. Just replacing the 02s without correcting the cause isn't going to cure the problem. As soonas they're replaced and you fire the engine, the codes will return because the CAUSE hasn't been corrcted.

So first you should investigate and correct - if necessary - any leak and then address the 02s if the codes continue to be set. If you do have a oil leak that's getting into the intake track chances are the 02s have been contaminated to the point that they'd need replacement.

A vacuum leak, however, may not effect the 02s long term, so sealing the vacuum leak may be all that's needed. Once the vacuum leak is sealed, the 02 codes should go away.

You can attach a vacuum gauge to the intake and see if the reading holds steady or if it jumps or is low. There are several ways to find a vacuum leak. From sparying carb cleaner around all the suspected locations, spraying an un-lit propane torch, etc.

In the past I've just use me water hose and flooded the intake where it mates to the heads. You'd have to be careful doing that though in order not to get water into the Opti or flood any of the sensors.

Probably the best way is to attach a scanner and check all the readings to see if any of them are out of range. Of course, you'd have to know how to interpret the readings.

If you post all the codes you're receiving probably someone can interpret them and point you in the right direction. The more detailed the information you give us the more likely we'll be able to pin-point the cause. One thing I definitely DO NOT recommend is just throwing parts at the problem; in the hope that one of them will cure the problem.

Hope this helps.

Jake

 

[Mark96CE]

Hi Jake

I am really starting to feel better about getting the car back on its feet. I am taking everyones advice and really trying to do things that wont have me buying uneeded parts. I have already checked the egr, I replaced the pcv vale. PCV hose vent hose, as they were diried up. I could not find any visible places where there could be a vacume leak, but I have only just begun. I did not check the intake manifold where the oil is leaking yet.

The code reader I am using is from Auto Zone. I really have not solved any problem yet, but at least I have a path to follow. You are all a great help.

These are the codes I am getting.
P031 - Bank 1 Sensor - censor circuit low volts

P0134 – CKT no activity

P0157 – Bank 2 – sensor 2 circuit low volts

P0300 – Detected multiple cylinder misfire

P0300 – Random cylinder misfire

P1133 – Manufactor controlled fuel and air metering

Mark...

 

[pkincy]

You need to check those codes in the Helms for your car. I am going to guess that all of your sensors are not toast. It more likely is a common short in the wire harness providing voltage to the Oxygen Sensors to get that many failures.

But you need to methodically run those codes and their diagnostics down.

Or as in another thread take the advice to take it to a dealer.

Perry