99 chevy 350...Fixed!

[Gary H NC]

My 99 Tahoe has developed a huge coolant leak.Its coming from the drivers side and dripping off the back corner of the head onto the bell housing.
I can not for the life of me get in there to actually see the leak.I can squeeze the radiator hose and hear it leak.So whatever it is has became a big leak.
I do not see coolant on the top edge of the head where it meets the intake manifold.There is a hose that runs from the front of the intake along the head and connects to the exhaust manifold.I do not think thats a coolant hose.It has a braided mesh sleeve over it.
I guess worst case is replacing the intake manifold gasket.Is that something a back yard wrencher like me should do? looks kind of intimidating with that plastic top to the manifold,all the wires and crap!
Any Chevy Techs got an idea what a shop would charge?
Thanks guys..

 

[SpinnerBait_Nut]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

Have you checked the freeze plugs Gary?
Might be one with a hole in it or pushed out.
There should be some on the rear of the head and block.

 

[SpinnerBait_Nut]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

PS, get a small mirror and hold it back in there with a shop light and you will see where it is coming from. It will be real clean.

 

[Ezrider_92356]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

if your decent with a wrench the intake manifold gasket is something you can do but i would suspect a freeze plug as previously mentioned. a light and one of them pencil type mirrors where you can swivel the mirror lots of different directions would be your friend in diagnosing this problem. if it turns out to be the intake gasket just make sure you take the time to label everything as you take it apart. it will greatly aid in putting it back together some masking tape and a sharpie will be your friend in doing this. the intake manifold gaskets are notorious for going out on the vortec chevy 350 but typically they leak threw the manifold gasket into the intake port though. i would recommend taking your time diagnosing the problem before you just start replacing parts that don't necessarily have to be replaced. even if you want to save money by doing it yourself you can take it to a shop and have them diagnose it for you for a small fee and tell them you do your own work it will still cost you less than paying 50 dollars an hour for the shop labor. they might even offer some advice for the easiest way to go about fixing it. most good shops are very helpful towards the back yard mechanic. iv even had a few diagnose some problems for me for free knowing that i had no intention of them doing the work.

 

[Gary H NC]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

Thanks guys. Been under it and no leaks around the freeze plugs.It is coming from the top. I can squeeze the top radiator hose and hear it squish out.Just cant see it.I'm going to go get a pressurizer and pump up the cooling system.
I had a buddy come buy and look at it,he is a good GM mechanic and he thinks it is the manifold gasket but advised doing the pressure test first.Its leaking to bad to drive it very far.
It seems like its leaking in the valley under the intake and running back,dripping onto the bell housing.
I'm thinking if i pump it up good with the engine cold i can see or feel where it is.
Did not want this job to do right here at Christmas...

 

[Solittle]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

I bought a 99 Yukon with the 350 a couple of years back. Same problem. It was the intake manifold gasket. You might Google this as I was told that this was a common problem. I had the dealer do it for $750.00. Far too many hoses, wires, sensors, etc., etc. for me to deal with.

 

[DJ]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

I bought a 99 Yukon with the 350 a couple of years back. Same problem. It was the intake manifold gasket. You might Google this as I was told that this was a common problem. I had the dealer do it for $750.00. Far too many hoses, wires, sensors, etc., etc. for me to deal with.

Agreed. That is my best guess especially if you say the core plugs are OK.

 

[Gary H NC]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

Solittle,I hear ya.I'm going to have to try it myself.I have been told its common on these engines too.
My neighbor offered the use of his heated garage so i'm going for it.
The gasket set is about 60 bucks.They list an updated type gasket that fixes the leakage problem.
Looks like if i unhook everything,put the ac and alt. to the side,pull distributer out,remove one valve cover and it should come off.Sounds easy huh? Doubt it..
I would much rather have a shop do it but thats more than i can spend right now. I have wrenched on many older GM engines but all those wires and hoses are a little scary!

 

[newbie4life]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

I bought a 99 Yukon with the 350 a couple of years back. Same problem. It was the intake manifold gasket. You might Google this as I was told that this was a common problem. I had the dealer do it for $750.00. Far too many hoses, wires, sensors, etc., etc. for me to deal with.

Me too. Mine was a 97 chev 350, and needed an intake gasket around 80k miles. The reason is a cast - iron block expands and contracts differently than the aluminum intake manifold. After a period of time, this is something that just needs to be replaced.

It seems odd to me that it's leaking that bad... mine had a small leak, but it wasn't anything that couldn't have waited for awhile.... I just hate leaks.

 

[Gary H NC]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

I'm surprised its leaking that bad if its a manifold gasket.I have noticed a small use of coolant over the last few months.Today it started really leaking.
I have been reading on some chevy forums that its very common.Thats a ton of work for a gasket.

 

[Windykid]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

Gary you might check with chevrolet as I seem to have heard about a service bulitin about the DEXcool anti-freeze eating the gaskets.

 

[SpinnerBait_Nut]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

I see no TSB for that problem.

 

[Gary H NC]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

It being a 99 model the dealer would not do squat! Not even going to call them and ask.
I was able to get a mirror and light back there from under the truck.Drivers side rear corner where the intake meets the block and the head.I can see where it is running out.No more diagnostics,i know what it is.
This is NOT going to be a fun one!
I did find out the valve covers need to come off also because the edges lip over the edge of the intake.
Only 8 bolts on a Vortec intake.Too bad everything else has to be removed!

 

[Xcusme]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

Gary, I feel your pain...I replaced the intake gaskets on my '98 Venture 3.1 last year at 68K miles (shame on GM). I did a lot of research on auto forums to see how others were handling the job. I did the masking tape labels, plastic bags etc and used the digital camera too. Pay attention to the torque values for the intake bolts and do not go more than the specs. Use loctite on the bolts too. It's not a hard job, just frustrating at times with all the hoses etc. I did have a legal pad handy and jotted down what was removed as I did it. Reverse the list to put her back together. Make sure the gasket surfaces are clean for both the intake gaskets and rubber seals etc. To be on the safe side I did an engine flush and oil/filter change too. It took me 12 hours start to finish, but I was being very careful. If I had to do it all over again (some guys DID have to re-do the job) it would not take me so long. Good Luck. p.s. I dumped the Dexcool and went back to Green.

 

[Gary H NC]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

Gary, I feel your pain...I replaced the intake gaskets on my '98 Venture 3.1 last year at 68K miles (shame on GM). I did a lot of research on auto forums to see how others were handling the job. I did the masking tape labels, plastic bags etc and used the digital camera too. Pay attention to the torque values for the intake bolts and do not go more than the specs. Use loctite on the bolts too. It's not a hard job, just frustrating at times with all the hoses etc. I did have a legal pad handy and jotted down what was removed as I did it. Reverse the list to put her back together. Make sure the gasket surfaces are clean for both the intake gaskets and rubber seals etc. To be on the safe side I did an engine flush and oil/filter change too. It took me 12 hours start to finish, but I was being very careful. If I had to do it all over again (some guys DID have to re-do the job) it would not take me so long. Good Luck. p.s. I dumped the Dexcool and went back to Green.

Thanks! Yea,i have been reading the same info.I will do the flush and oil change for sure.
When pulling the intake off as one piece do the injectors just need unplugged? I can't see those little plastic pieces of junk from the top.
Got all my tools together,just need to go get parts,Loctite and anti-sieze if any needed.Guess i'll get started on it tomorrow.Like to be back on the road by monday.Its my only vehicle right now...

 

[MikDee]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

Hey Gary, Sorry to hear about your problems, I know this happens on these trucks, also on the 4.3 Vortec V6 like mine in the S-10, and it's a pain in the *****! "I'm just waiting for the other shoe to drop" if you know what I mean, when it happens, I hope it's in the nice weather. I had to do this on my 88' Monte Carlo SS 305 HO, and I know a bunch of people that had the same thing happen, and they weren't Vortechs, but ever since they've started using factory aluminum intake manifolds. Good Luck, and be careful, I know this is tough on the back.

 

[Windykid]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

I see no TSB for that problem.

Niether did I, a friend of mine mentioned it to me once. I couldnt understand how dex cool which is supposed to be less corrosive than the old would eat the gasket and seal.

 

[Gary H NC]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

Thanks MikDee,
I'm pretty sure i can do the job but busted knuckles and a few swear words are a given!
At least i have the neighbors warm garage to work in
I would hate to do this job outside period.I like having tables and benches to keep everything sorted out.My neighbor is pretty good with a wrench too..guess i'm buying the beer...

 

[SpinnerBait_Nut]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

Probally not the dex cool, maybe an engine design flaw.
Like the Subarus when they first came out with the 2.5L engine in '99 or 2000 with bad head gasket material.
About all of the first ones made failed and had to be replaced.

 

[TilliamWe]

Re: 99 chevy 350...help!!

Re: 99 chevy 350...help!!

GM dealers swear the DexCool doesn't cause this problem. But they have this problem with iron head engines (5.7 and 4.3 Vortecs) and aluminum headed engines (3.1 V6 and 3.4 V6). So other than the iron blocks, tell me what's the common factor? DexCool. Whether it causes the problem or not, DEFINATELY get rid of it during this repair.
(BTW, the slow disappearance of coolant you had been experiencing, was probably the DeathKill evaporating, leaving behind the brown sludge in your radiator. All GMs do it)