Probably IM gasket - do I need to bite the bullet?

[rationull]

This is probably going to sound like a case of neglect.

A used oil analysis on our 1999 Suburban from a little more than a year ago came back with coolant in the oil. I posted about it here.

I got another used oil analysis 6 months/750 miles later (to confirm it wasn't just errant coolant poured into the oil fill hole or something) and it showed the same trend. I'm working under the assumption that it's the intake manifold gasket since that's a known problem on GM V8s from the 90s but technically I don't know what the problem is.

In a nutshell, the vehicle is used primarily for towing. It gets 1500 miles or less put on it in a year. The coolant level does not seem to visibly drop aside from ambient temperature changes. I took it to a shop initially and for whatever reason they said they couldn't find any evidence of an intake manifold gasket or head gasket leak (they did a "block test" and looked for evidence of external leakage of coolant around the gasket, I think). But, the used oil analysis doesn't lie...

Seeing as it's summer, it's towing season again for this truck. Specifically my wife wants to tow in another couple weeks probably. I'm trying to decide how serious I need to be about taking this somewhere else to get reevaluated. On the one hand I want to think that it's not that big a deal since the coolant level doesn't seem to drop noticeably and since the oil gets changed so frequently (mileage-wise -- I change it once a year). I just spent some money getting the ball joints replaced and replacing the tires on another vehicle so I'm not excited about spending more car money right now, either.

But obviously I don't really want to kill the engine. The bottom line is if it could go on like this for another 5 years then it might not be worth it to me right now. But if I'm really making a significant dent in the engine's life (it's got about 165k miles on it now) then I could probably scrounge up the cash. I don't particularly want to tear into it myself (although I probably could do it).

So am I OK ignoring this or do I need to stop being lazy about it?

 

[rclint]

Go to your local GM dealership ask them for the coolant stop leak tablets, they pretty much have to use these tablets on many engines ( I heard they were invented for the Cadillac) I have used these before with outstanding results. In your case the small minuscule leaks would be well worth the expense of these ( ~$10) and chances are even if you had the intake gasket replaced you may still end up with a small leak from a high tolerance part etc... it may have had this leak since new..

Also Bars makes some Gold tablets now, that's the name of them you may find them at AA, AZ, or walmart they work every bit as good.

 

[NEOhio_Bob]

I don't think there's enough information here to make a call. Is the truck running well (i.e. would you even suspect anything was wrong if it weren't for the UOA)? How far are you towing? How heavy is the trailer? What's the terrain? If you're towing a heavy trailer across the desert in mid-summer, I wouldn't do it. If you're towing a pop-up to a campground 50 miles away, that might be another story. BUT, as soon as the coolant starts disappearing at a noticeable rate, or there are drivability problems, you probably need to bite the bullet. Hot weather and heavy loads have a way of turning small problems into big ones...

The GM stop leak tablets are a really good idea. It can't hurt, and it might at least buy some time.

 

[rationull]

The only thing that comes to mind as kind of running/drivability problem is a slightly uneven idle, but I doubt that would be related (I'm currently blaming it on the plugs which I need to replace -- no idea how old they are). It runs smooth and pulls strong. I would definitely not suspect any problem if it weren't for the UOA, and I have no way of knowing how long this has been going on. We bought it 2 years ago and have only put about 3000 miles on it.

It tows a two horse trailer with either 1 or 2 horses in it. I don't know how much the trailer weighs but I'm guessing that with 2 ~1200 lb horses in it the whole load is probably less than 6000 lbs. Generally it'll be towing 60 miles or less in a day, round trip. As for the terrain, it's fairly flat with rolling hills, BUT some trips include a 3 mile ascent on a 7% grade (well, all trips include the hill, but only some include towing up it).

No argument and I will get this taken care of quickly if I notice the coolant disappearing or anything like that. The fact that the problem is so ignorable right now is what's making me unsure.

I hadn't thought about the stop leak tablets! Maybe I'll go get some this week...

 

[rationull]

And I guess one more question while I'm at it. I'm assuming the IM gasket replacement procedure has a chance of contaminating the oil, such that if I end up getting it done, I might as well wait until afterwards to give it an oil change, right?

 

[The_Jeff]

If you dump the antifreeze and run pure water with some sort of water pump lube it will buy you more time. It's the stuff in coolant that trashes bearings etc. Water will evaporate off, more or less.

 

[Trav]

Originally Posted By: rclint
Go to your local GM dealership ask them for the coolant stop leak tablets, they pretty much have to use these tablets on many engines ( I heard they were invented for the Cadillac) I have used these before with outstanding results. In your case the small minuscule leaks would be well worth the expense of these ( ~$10) and chances are even if you had the intake gasket replaced you may still end up with a small leak from a high tolerance part etc... it may have had this leak since new..

Also Bars makes some Gold tablets now, that's the name of them you may find them at AA, AZ, or walmart they work every bit as good.


The Bars Leak Gold powder and tabs are the same as the GM tabs,AFAIK they are both made by Bars Leak.Ginger root is the ingredient,it swells slightly when it dries in the presence of air. 1 tube powder = 1 tab.
GM recommends putting the tabs in the lower radiator hose on cars with no radiator cap.

 

[SteveSRT8]

you can get them at NAPA, we pay less than 4 bucks for the set of like 6 tabs.

 

[rationull]

Do I need to dump and change the coolant to add the tabs or can I just put them in an already full system?

 

[The_Jeff]

I would at least dump some to "wash it down", the stuff tends to float on top. Maybe dump a quart into a 1/2 gallon container, add the tabs, cap it, shake it real good, dump that in and start it up.

On my cap-less car with surge tank I drain that much so the surge tank is empty and my solution makes its way into a bypass hose that's always got flow.

 

[rationull]

Hmm.. I've got a bottle of this (Bar's Heavy Duty Radiator Stop leak original pelletized formula) sitting in my garage, still sealed, that's probably 5 years old. Not sure if that would work (but I'm sending an email to the company asking about the shelf life). I'm not so cheap I won't buy some newer stuff but if that'll work I might as well use it because it's sure as heck not going in either of our other cars any time soon

Should I give this a shot or look around specifically for some of the Gold powder tablets or some of the GM ones?

 

[rationull]

I called Bar's customer service and they said that I shouldn't have to worry about shelf life on that product and that a 5 year old bottle should be just fine. So I guess it's down to 3 choices:

Bottle I have
Tablets (which appear to be basically the same stuff)
Something more extreme

I'm tempted to just throw in what I've got but that last one in particular actually mentions intake gaskets. But, it also seems like it's for larger leaks.

 

[rationull]

I ended up buying a couple packs of the tablets (1 pack treats 3 gallons of coolant capacity, this truck has 6.8 gallons). I didn't bother evacuating any fluid because I figured there was enough room in the big side tank under the radiator cap to hold all the tablets, but it turned out to be pretty tight (obviously the tank has plenty of volume but there's an oil cooler or PS cooler or something in there taking up some space). I had to shove a screwdriver in there to lightly break some of them up in order to fit the last two tablets in.

Took it for a nice long drive and everything's normal. I'm hoping not to find a sludgy mess in there in the morning when it's cool. The plan is to change the oil next week sometime (it's due), get another sample in 6 months/750 miles or so, and see if it helped.

Thanks for all the help, guys. If this works, it'll be $7 well spent

 

[rationull]

Opened the rad cap this morning. No sludgy mess but the coolant I can see at the top of the rad (where I put the tablets in) is not quite as clear as it used to be, which doesn't give me a warm fuzzy feeling. I hope the stuff made it all the way through the system.