1998 Tahoe/ Gasket issue

[TCMERICK]

OK, here is my issue. Last friday I started up my Tahoe to drive home and noticed a heavy white vapor coming from the exhaust ( had not seen it before). I put my hand into the exhaust flow and then sniffed it to see if I could find any unusual odors. I could not smell any oil, but I think I detected a bit of water/coolant. The same thing occurred this morning, both times however, after the engine ran for a bit the heavy vapor got noticeably better.
There is no sign of water in the oil, but coolant does seem to be getting lower, and oil pressure is good, water temps stays at around 190-200 (with 190 thermostat). I think I can rule out blown head gaskets, and have heard that the 350 Vortec's are prone to bad intake gaskets (is this truth or rumor?) I am iterested in any feedback. I was also wondering if my intake gasket is bad, with 141,000 on the engine, would it be a good idea to just replace the head gaskets as well?
thanks in advance.

 

[NousDefions]

Lower intake manifold gaskets are a 100% failure item on these vehicles. Swap it out with the good rubber and steel gasket from Felpro and you'll never have an issue anymore: part number MS98000T is a kit that comes with everything you'll need for the swap, including a single valve cover gasket for the passenger side cover that needs to come off.

Here's a great writeup of the process. Be SURE to mark your rotor cap and distributor, or you'll have to re-time the engine after you are done. Everything else is pretty straight forward and easy. Should take 6-8 hours.

http://d-tips.com/general/articles/article.aspx?id=11

 

[lesterl]

Definitely failure prone on these motors. Hope that is what it is. Stop running it and replace the gaskets. I would pressure test the radiator to see if you have any other leaks, when done change your engine oil also....

 

[TCMERICK]

Nousdefions and lesterl, I replaced the head gaskets as well as the intake manifold gaskets. The lower intake manifold gaskets were both actully broken and that was where my issue was. I replaced the head gaskets just because I wanted to check my cylinder condition. Nousdefions, I took your advise and replaced my lower manifold gaskets with the felpro rubber and metal ones, and I am glad that I did. (I do not want to have to do this again. Before your reply I had already bought a gasket kit that had the cheap plastic gaskets in it, but I spent the other 60 bucks on the kit you mentioned, I and think that it is money well spent. The metal and rubber gaskets have alot more sealing area on them and I think they will work best for anyone especially if their intake manifold is pitted. I just want to say thanks again to both of you for your advise.

 

[lesterl]

Didja change the oil afterwards?

I am a MAJOR fan of the Felpro Permadry Plus gaskets (rubber over steel backer). Only way to go on a GM engine.....

Glad ya got it going.....

 

[TCMERICK]

Yep, I did change the oil, I usually run Amsoil, but since I did not have any of that around I got a top quality Fram Oil filter and am runnig Mobil 1 5W-30 extended life full synthetic for now. I also replaced the fuel filter and put in a new injector set up as well as a volant cold air intake in the hopes of getting better gas milage, I am also running a G-Force chip. I am running JBA headers into magna flow converters and a flowmaster single muffler exhaust. Hopefully, that will get my gas milage into the 16s or 17s from a pretty solid 14 MPG prior.
I am curious about one thing though, My repair manual says that timing in a 350 vortec cannot be set with a timing light, but must be set with a scan tool, and what you are actually setting then is the camshaft timing. Is that accurate info? Also, If the rig is starting just fine, runs well with no service engine light on, can I assume that the cam timing is good, and taking it to a mechanic or purchasing the correct scan tool is not necessary? I have a fair amount invested in this repair and don't want to ruin an engine.
Your thoughts?

 

[lesterl]

I would say if no light is on you are golden. There are some who report that a CKP relearn helped with mileage. IMHO you wont ruin the engine AFAIK they use that signal to detect missfires that the Knock sensor doesnt pick up (crank rotation slows slightly). Timing is fixed, the distributor base should have a key in it and you need to get the teeth meshed right, the actual timing is adjusted electronically by the ECM....

 

[TCMERICK]

lesterl, I first want to say that I typically trust everything that you post and that I truly do respect your knowledge and experience; However I was still concerned about not having my engine timing (camshaft retard- as GM calls it) set properly and how it might effect engine performance, so I took my rig to a shop this morning just so that I could have peace of mind that that my ignition stuff was straight. The mechanic stated pretty much what you said, and did find that my stuff was off 9 degrees. He also let me know that I had infact set the distributor in correctly and that cross fire was not going to be a problem.
The bottom line is that my rig is up and running and I am confident that my engine issues are over with for quite a while, thanks for all of your support, I appreciate it!

 

[NousDefions]

lesterl, I first want to say that I typically trust everything that you post and that I truly do respect your knowledge and experience; However I was still concerned about not having my engine timing (camshaft retard- as GM calls it) set properly and how it might effect engine performance, so I took my rig to a shop this morning just so that I could have peace of mind that that my ignition stuff was straight. The mechanic stated pretty much what you said, and did find that my stuff was off 9 degrees. He also let me know that I had infact set the distributor in correctly and that cross fire was not going to be a problem.
The bottom line is that my rig is up and running and I am confident that my engine issues are over with for quite a while, thanks for all of your support, I appreciate it!

If you put the distributor back in off a tooth, it simply wouldn't start. I'm not surprised you are off by a few degrees, though. It's hard to get it back perfect.

 

[lesterl]

Glad you got it going, and running the CKP Relearn isnt a bad idea......