Phnx1

i had the intake manifold leak, it hydrolocked when starting after hours of rain. what a nightmare. sounded like a sledgehammer on the block. The water was coming in thru the fake hood vents on the 94Z or the cowl.

had to pull the plugs and turn over. water shot out in all directions. no coolant in it. had a shop do the seal and its fine now. nothing bent i think as it runs smooth. As said, the engine is sealed normally so water should not enter it regardless except thru the intake if you dive into a deep puddle, another nightmare i have avoided so far. K&N intake with Amsoil blue cone

RockinWs6

NOWAY this can't happen

speedychevy

I'm hoping to revive this for a bit.

Does anyone know if there's a write up on this anywhere? I was washing my car the other day, and I noticed it was leaking through the cowl pretty bad on my '01 camaro. I've also noticed that after a heavy rain, They'll be some slight hesitation and a mid-range RPM backfire for the first few minutes of driving. Probably the coils getting wet?

So I bought some 3M weatherstripping sealant to do this job, but now I'm thinking I need something else because in most of the posts I've seen, people are using silicone to seal up the cowl. Any suggestions? Pictures would be great as well

Paul Bell

iTrader: (9)

I think this is as close to a write-up as you'll see. RockinWs6, feel free to do a write up and post it in this thread.

FWIW, when my '99 was a daily driver and saw a lot of rain while driven and parked, I never had this problem. I'd like to point out the I've removed the rubber seal molding from the rear hood edge to allow air to better flow out of the engine compartment so any water dripping issue would be worse. I've never had this problem (water getting the intake ports) perhaps because my intake manifold bolts are properly tightened.

Yenko Deuce Nova

Most would never think that rain water through the cowl seal would hydro lock an LS1, but its true. My 17 year old son's T/A was in the school parking lot from 7AM till 10PM in the pouring rain. He got in after his football game was over, and upon startup the engine sent rod #6 right through the side of the block - never even took it out of Park. The car is (was) bone stock, with 65k miles.

We assumed it was a cracked a flywheel, and ordered a new one along with a torque converter, a shift kit and an external trans cooler. Then found that it was a rod. During tear down, about 6-8 ounces of clear water came out of the intake. Once we had the cylinder head off, we were even more surprised to NOT find anti freeze in the cylinder, just more clear water. While my son was anticipating the performance upgrades we could (and did) include, I was searching for a cause. Here is the conclusion.

The factory cowl seal indeed drips water onto the top of the intake in about 8-10 locations. Generally, this is not a big issue - many of us have degunked an engine or two in our day and the biggest concern is the distributor or coil (packs). However, because of the expansion rates of dissimilar materials of the intake (plastic) and cylinder heads (aluminum) the intake bolts tend to loosen over time. This would typically throw a code for a vacuum leak, but that rarely happens because the materials expand upon startup and close off the gap. If however, the materials cool down, the bolts are loose, the car sits in rain for several hours / days, and the cowl seal is dripping - well, water pools on the intake and will seep down past the intake and/or injector gasket(s). In about 90% of the cases cylinder #6 is the leaker, which will hydro lock if the piston is at the bottom of the stroke.

If you are lucky, it will start hard and push out the water. Bad case scenario it will minimally hydro lock and sometimes pull the starter bolts out of the block. Worst case scenario it will bend the rod, the counter weight will come around and twist-break the rod and send the loose end into anything in its way - like the block.

To say we (I) was stunned is an understatement until I started reading up on it. To be honest, I would feel better if my 17 year old had over revved it. But, in the end it now has a fair amount of performance upgrades on it, and I need to seal the cowl up. So, I bought a tube of GE 100% silicone and since I don't see any other pics on how & where, I'll likely use the entire tube.

Will try to add a pic of the carnage...

Edit: can't seem to add any jpg's via 'Manage Attachments'

RockinWs6

I got lucky 2 or 3 times until I realized wth was going on. Every time it rained and our 02 Formula sat outside overnight the engine would lock up as it started. At 1st it happened so fast I didn't think too much about it BUT the last time it locked HARD stopped then bam it started. I immediately shut off the engine and stated looking for a explanation. It was still raining and I popped the hood and watched as water sprinkiled in about 10 places onto the engine laying along the intake. I knew right away what was going on. There was no warning for a vacuum leak etc engine ran fine etc. ALL the intake bolts were loose! I sealed all along the cowling and the plastic rivets and tested it with running water until it didn't drip anything on the engine. Crazy start never happened again.....now the 1st I do when I get a fbody home is seal that cowling and rivets.

RPM WS6

iTrader: (3)

It sounds like the root of the problem is loose intake bolts, so checking them for proper torque should really be the first order of business. If everything was tight, it shouldn't really matter how much water leaks through the cowl area (or not), unless there is some evidence to support the root problem being injector O-rings (though this would be harder to quickly verify than simply checking intake bolt torque). Nothing wrong with sealing up the cowl area, but the first order of business should probably be to fix the root issue since the cowl may eventually begin to leak again at some unknown future point.

FWIW, I've never seen this problem on any of mine, and the cowl seal was definitely leaking on my '02 car (intake was often wet after a lot of rain or washing). I don't deny the problem, but I don't think it's as widespread as some folks have implied (i.e. this is not certain to happen with every example). But it's a good idea to be aware and take proper precautions.

Yenko Deuce Nova

Agree, 100%. The root cause is def the intake bolts not the leaking cowl, but for this event requires a combination of failures to occur under the right circumstances - we even factored in the angle at which the car was parked during that rain storm, realizing that it made the intake around cylinder #6 perfectly level and thus allowing for zero natural drainage. But, we (he!) sealed the cowl last night (only used half the tube) and we will torque the intake bolts at each oil change from here on out. He has invested a fair amount of $$ into the performance upgrades during the rebuild process, and we don't want this to happen again!!

RockinWs6

Well the bolts feel tight but the intake is loose. You need to break them all loose a full turn then retighten. The threads get crapped up with dirt etc but the intake is loose COLD, Warmed up the engine the intake expands enough to seal up so you never get a lean condition code etc. I always wondered why the car would run so rough on a cold start but idle perfectly smooth warmed up and the bolts felt tight. Eventually I removed the intake to replace the intake gaskets, we spent a lot of time cleaning the intake bolt threads.
Now on my WS6 I found the same condition, terrible cold start idle that smoothed out as it got warmed up. Bolts were tight checking them but the intake was loose. Pulled it apart cleaned all the threads no more rough cold idle.

I've seen this so many times over the years, honestly the 1st time I popped the hood when it was raining out I about sheet. On the v6 Camaro we bought every time it rained the engine misfired badly. Water was dripping down all over the ignition coils shorting them. Sealed the cowling and it ran perfect.

AnotherWs6

iTrader: (17)

FWIW Felpro intake gaskets are beefy as **** for ls1/6 intakes. I have seen several sets of them. Also, when you take a manifold off with factory gaskets the gaskets are usually pretty smushed down, almost level with the maifold itself. Not so with Felpro - they seem to pop right back out. Def a good upgrade if you're having issues with your manifold.

AnotherWs6

iTrader: (17)

And holy F at flaming the OP. He brought up an issue I've read about a **** load.

RPM WS6

iTrader: (3)

I'm sure you're right about the "perfect storm" combination of circumstances, otherwise this problem would be much more common.

That's definitely going to be overkill, but I do understand how you guys must feel after experiencing this.

Interesting, good info. I've never had any cold start/rough cold idle problems on any of mine (other than tuning related issues immediately after a cam swap), even at 100k+ miles. Perhaps that's why the leaking cowl never caused a problem on mine (i.e. intake hadn't worked loose). Sounds like the rough cold idle is a warning sign of the potentially loose intake (which could obviously lead to this water intrusion problem under the right conditions). A good thing for folks to keep in mind.