CamaroUK

So I'm one of the many people that had the infamous LT1 intake manifold oil leak.
The first time I addressed this I found the factory silicone in place so I knew I was the first owner of this car to have the leaky intake problem.
I fixed it all back up, it seemed alright for a little while but then started to drip a little.
The day came when my annual MOT inspection was due. During the fast idle test the car was at peak operating temperature with the maximum fan operation cycling on and off, and well...the floodgates opened. Oil was literally trickling from the back of the oil pan and had made a huge puddle on the pit floor in less than two minutes!

Here's a video of he carnage on the top of my gearbox:


I redid the fix with a different brand of silicone, that held solid for 11 months before starting to drip occasionally.
I will note about 8 months into this fix I started to notice milkshake in the oil fill cap
MOT was due again so I redid the fix for a third time just one week before the inspection.(I noticed some milkshake stuck to the underside of the intake but thought nothing of it)
It started to drip bad just at the end of the test, within days it got gradually worse until the oil level went from full to nearly off the bottom of the dipstick
So for the fourth time the manifold came off, this time I remembered the milkshake issue.

And so I come to the point of all this...

Curiosity made me undo the 4 bolts holding the oil splash guard from the underside of the intake manifold, and...carnage!!!
The entire cavity, including the PCV port were completely plugged with sludge. It took me an hour to clean it all off with a paintbrush, petrol and lots of rags.
I cleaned the cavity, the intake pcv port, the pcv valve, the rocker cover to tb breather pipe, the tb itself (which I might add was so badly plugged that vacuum and heat had sucked the rubber gasket into contorted disrepair).
Put her back together
Topped up with fresh oil
Now to see if its cured but I 100% suspect I have solved the problem. I don't have a bad blow-by issues but I do suspect the normal crankcase pressure, unable to escape forced its way out of the weakest link - and we all know where that is on an LT1!!

Moral of the story, if you have the intake leak or even if you have the intake off - CHECK AND CLEAN THE PCV SYSTEM!!

I'm sorry if this is a repost but I just wanted to share my experience.
I'm also sorry for the bad structure of this post but I'm quite drunk...haha!
One more thing, if my intake leaks again, I'll buy a hat and eat it

CamaroUK

Couple of other tips after doing this 4 times:

Bungee straps - invaluable for holding the wiring harness out of the way while you place the manifold back on. I used 4.
Putting RTV silicone on the underside of the intake end mounts 24 hours before install - eliminates the worry of scraping off fresh RTV silicone if you decide to silicone up the block side of the assembly immediately before install. Also means you don't have to mess about reaching deep into the engine bay to clean, prep and RTV silicone-up the rear of the block.
Personally I did both for my own piece of mind - I mean please, this is my 4th time!!

And yes I'm more drunk now lolz...

94blackz

Good to know im pullin mine this weekend and will repeat this process thakns.

Chevyman5436

I had a coworker with an LT4 that had the infamous oil leak. After trying 5 times of resealing, he took an hammer and a small pin and hammered in small holes or dents into the intake manifold and block and the silicone would groove into the holes and keep it in places. Pretty neat trick for anyone wishing to tackle this.

96capricemgr

iTrader: (1)

I would be a bit concerned about what caused the sludge?????

Thank you for sharing your diagnosis about a PVC fault likely contributing to the recurring oil leak, seems perfectly reasonable and most would overlook it as you did the first few times.

leadfoot4

iTrader: (1)

I'm the original owner of my '96 Z-28, took delivery of it in late October of 1995. For me, the silicone at the ends of the manifold lasts 3-4 years. The first repair was while the car was under warranty, and I've don it myself 3 times since. A while back, I thought I read somewhere that the proximity of the EGR pipe to the rear of the manifold, was "cooking" the RTV....

shbox

My intake was last off more than 9 years ago (actually kinda hard to believe, LOL). Ultra Copper was used to put it back. Still dry as a bone (I just looked at the back with a mirror).

Kevin97ss

Another helpful tip is to use one stud on the rear most drivers side head. It will prevent you from bringing the intake in at too steep of an angle and scraping the silicone away on the thinnest area of the block land. Also it keeps you from needing to reposition the intake once it is set down. Gives a nice even squish every time.

shbox

The stud tip is part of the instructions on my website. I use one front and back on one side (you can't use them on both sides because of the turned in angle).

Camaro350Z28

iTrader: (6)

i havent had a problem with an intake leak since ive switch to using the right stuff.

cbyoung93

I have a major oil leak when. I go through 3 quarts of oil on a 2 hour road trip (150 miles). I use 10w-30 royal purple oil on my 5 .7 lt1. I have owned the car for about 3 years. It had a problem when I first got it and got it looked at. I was told then that it was the crank shaft and had it replaced. The entire underneath of my car has oil caked on everything. My oil guage usually sits around 60 when im driving and 40 when idling. I'm spending so much money on oil and really wanna figure it out. There's not really much oil on the top of the engine. Everything is underneath. It's a 1995 trans am and it has 70k miles with everything still original, with the exception of ram air. If more information is needed to find out what's wrong with, please let me know and I'll get it for you. Any help is appreciated. Thank you

BTC

Check the rear of the intake manifold where it sits on the block. That's a common leak point. You will more than likely need a mirror.

The seals in the timing cover for the optispark and water pump are also common leak points.

There may be others such as crankshaft seals etc.

Based upon your description of the underside of the car and the amount of oil you are using, I suspect you have multiple leaks.

BALLSS

that much oil loss should be pretty clear where it is coming from....at least front/back/top/bottom of engine

there are several seals that like any other car can leak. It could be your oil cooler lines or oil filter adapter gasket...or pan or front crank/Timing cover seals...or....so you see it could be so many things you need to clean your engine enough to then drive some and see where it leaks...

The rear of the intake is a common leak and most see it as oil around the bottom rear of the motor but it just drips down from the top rear. run you hand along the back of the intake where it meets the block...if it is wet oil you have a leak there...and likely more

I would first look close at oil cooler lines and oil filter adapter area as you are pumping out a but load of oil. Either of those repairs will be lees painful as other possibilities.

You just need to do enough looking to find it....including getting uner the car to see wtf might be going on

In the mean time if it is puking that much oil...just get generic brand bulk oil.....it isn't in the engine long enough to matter if it is high $ stuff.

cbyoung93

I'll give that a look and see if there are multiple at those locations. How much would you guess that will run me to fix?

BALLSS

....it would depend on what in fact is the source of the leak. Gaskets or seals are not much $ at all......but if you pay a shop to do the work it could cost hundreds of $ to put in a $12 seal....again just depends on what the source of the leak is

If you have the ability to do this kind of work yourself....none of these parts are much $.

BTC

I only have experience doing the intake and optispark and water pump seals. If you do the work yourself, it won't cost much at all. If you have someone else fix it, I really can't say. The cost will also depend on exactly where you are leaking.

If you have the time and any mechanical inclination at all, I would recommend doing it yourself. It's not that difficult addressing most of the leaks mentioned.

As ***** mentioned, given the amount of oil you are going through, it should be fairly easy to identify a culprit, or culprits. I know when the seals in my timing cover were leaking, it was very easy to see the oil coming out when laying under the car.

if the rear of the intake is leaking, you'll know that too. You could just run your hand along the rear of the intake and it will probably be covered in oil if you have a leak.

How long have you had this car.

cbyoung93

Thank y'all so much. I just never knew exactly what to look for. I'm trying to learn more about my car at the same time as fixing it. I've had the car for 3 years now, but it was in storage for 1 and a half.

BALLSS

OP

FelPro makes good seals and gaskets. You can buy the front timing cover seal/gasket kit for $12 at just about any auto part store.

If it is your intake manifold leaking get the Fel Pro "printle" series of gaskets vs the regular ones (the printo have a blue sealer seam around each passage.)

if it is your oil cooler lines those can also be purchased at most auto part stores but are likely aftermarket (doorman) ones.

As I mentioned you may need clean the engine enough to reveal the source of the leak if the motor is covered in oil and grime. Grab some quarters and go to the local spray wash....although take care in not blasting the opti spark with water

I think a flash light, you getting under the car and just looking and wiping your hand across the rear of the intake where it meets the block will tell you where your leaks are coming from.

Dirty_Bird

I use international rtv, put that stuff dries to like a silicone rubber like substance, use it on big rigs. No leaks at all on my stuff.

aroberson77

When mine was leaking oil was literally getting everywhere and my car actually caught on fire cause oil got on the exhaust. I would pull the intake manifold and get new gaskets and good permatex or other quality brand silicone. The trick is to get a large bead, but dont clog the passageways. Also make sure you seal all the way to the intake gasket. I believe shbox.com has a good writeup on removing the intake manifold