Hello, I'm looking at a 1997 Olds Bravada that is in really great shape but the owner says that there's a small coolant leak. He cannot find where it's leaking, but it's slowly disappearing...

Is this a common problem with the 4.3L? What could this be? A bad head gasket? Are there any on-the-spot checks I can do to rule a bad head gasket out... I test drove the truck, it drives fine, the engine is strong with 147K on it.

I am interested in buying this SUV because I got into an accident with my 1997 S-10 Pickup 4x4 (173,000 miles) and since it was flipped on it's side, the body-work repairs are not worth it. The engine, though, was replaced with a remanufactured long block and has about 2000 miles on it. Having a bad head gasket really isn't a huge deal to me because if the engine is really bad, I can just swap the remanufactured one in, but of course, I'd rather not have to do that...

The owner also has the thermostat that needs to be installed because the temperature would rise slowly. He already replaced the heater core, intake manifold gasket, front wheel bearings, shocks all around along with new front U-joints.

 

Most likely is a blown intake manifold gasket (even though the owner states it has been replaced). The integrity of the head gaskets can be checked with a compression check although that is not too on-the-spot...

The intake manifold gasket is not too difficult to repair, but you must make sure that the cooling system has not started to rust due to an air entrapment situation.

On other things to check, I would drive the truck in some tight circles as well as make sure that all of the tires have even wear patterns. Driving in tight circles may show a problem with the AWD system as will uneven wear patterns.

 

So the truck has the common "Dex-Sludge" in the radiator neck so I will be doing a flush with Prestone Heavy Duty Cooling System Cleaner as per the GM Service Bulletin. It now makes sense why the PO replaced the heater core and intake manifold gasket, both prone to damage when Dex-Sludge exists.

I plan on changing out the thermostat tomorrow as I get only a little heat in the truck and the temp gauge barely raises above 110F or so... The PO already had the thermostat in the truck with the gasket but never got around to putting it in... When I step on the accelerator, I get a "gurgle", though, from the heater core, whats the best way to remove the trapped air? Should I run the engine with the radiator cap off, on ramps maybe? It's hard to actually flush it now as we are currently getting a bit over a foot of snow tonight... I can flush the system at school in my auto class but I'd rather do it right with the whole "run it for 3 hours at 1800rpm" method, and that's not possible to do at school...

Nick

 

Misconceptions I am sure. Long, but good information. Especially on the last page. Since we already have a thread that covers the coolant issue quite well, we do not need to continue the discussion here.

If you are doing a flush, just get the air out then. The best way is to elevate the front of the vehicle with the passenger side slightly higher than the driver. Run it through a few heat cycles and you should be good.

 

So I installed the new thermostat today and now I get the engine temp up to 210F then it drops to about 160F-175F or around there... Before, it wouldn't get above 100F... I parked the truck on my grandparent's very steep hill of a driveway and did the "burp" there. I let the engine idle for about 15 minutes with the radiator cover off and filled it with coolant to the top. I came back about 15 minutes later and I couldn't see any coolant in the radiator... So I filled it back up probably about 1/4 of a gallon, but the overflow tank is still at the right level.

And I'm not getting any heat at all... And when I move the selector to cool you can hear it change over and back... But, I guess, at least the engine is heating up correctly.

I have noticed that where I park, there's a spot of orange-brown colored fluid in the snow, which of course is the coolant... Where are some common leaks when the Dex Mud is present? Again, the heater core and intake manifold were both replaced along with the tstat.

Nick

 

You will need to check the freeze plugs (2 on each side of the motor), the heater hoses at the firewall/engine, radiator hoses, water pump, thermostat housing, and the intake manifold where it meets the head. I am sure that there is someplace that I have missed... Oh yeah, head gasket... Typically a head gasket leaks internal to the motor, but I have seen some where they have leaked external. A cracked block is also a possibility...

And I really hate to repeat myself, but just because someone said that the intake manifold gaskets were replaced does not mean that they were or that they were installed correctly... The first thing I do with vehicles that are having somewhat chronic problems is check over any recent work regardless of whether I was the one that performed that work or not (even more so if I did not).

You may want to get a some radiator dye. Put the dye into the system and drive it around for a few days. Then look under the hood with the UV light and the cool orange/red shades. The leak should be very apparent.

 

After starting the truck and running it, I've checked under it and noticed that the coolant is running off the bottom of the block, it doesn't look like it's coming from the pump though...

And here are some pictures of the radiator and tank:

http://i12.photobucket.com/albums/a2...Picture002.jpg
http://i12.photobucket.com/albums/a2...Picture003.jpg

Nick

 

What part of the block? Front? Back? Left? Right?

 

I am more interested in pics of the coolant leak.

Where is the leak under the truck/ Drivers side, passengers side, front back?
Do you see any ANY moisture on the block where the intake manifold makes contact, particulaly the corners, especially behind the power steering pump?
After it starts leaking turn the engine off and find the bleeder hole on the water pump, is it wet?

Do you have white smoke out the tail pipe?
How fast does the coolant disapear?

Lots of questions eh? However I have a coolant leak means diddly to me! You need to be more specific.

 

Yes, lots of questions, but if it can get me to a solution, I'll answer 1000... lol

The leak is on the front of the block, dead center, all the way at the bottom. I can see two streams under the lowest pulley. In the middle of this area, it looks like there is an electrical connector of some kind. I will get a video tomorrow afternoon and post it... When I burped the system, I opened the radiator cap and filled it to the top. After 15 minutes of running the engine, the coolant level was down past the metal "innards" of the radiator. It looks like a pretty significant leak... I'll have to do a "___ minutes for one cup" kind of test tomorrow.

There is no white smoke out of the tail pipe. Where is the bleeder hole on the water pump? I'll have to check for the moisture around the intake manifold.

If the previous owner *has* replaced the heater core and intake manifold, would running this bad fluid through cause any significant damage whereas the heater core and intake manifold would need to be replaced again, if the work was done a few months ago? I'm pretty sure the heater core was done because the dash was taken apart and one holding tab was sticking out (which bothered me enough to fix it...) and there's already a fitting on the heater core hose, the right one I believe, and in the cup holder is the garden hose adapter...

Nick