Chevy Vortec Mystery Coolant Leak
January 4, 2009 by Eric
If you own a Chevrolet or GMC Truck with a Vortec Engine, you will eventually encounter the "Mystery Coolant Leak".
At first, it's just an occasional low coolant light coming on. The coolant level is low, but there aren't any leaks visible on the ground. Where is the coolant going?
Eventually, months maybe, there are telltale drops of coolant on the drive way after the truck sits overnight. On the frame underneath may be a drop of coolant about to drop right in the center of the truck. It's starting to look like it needs a water pump maybe, but when we climb underneath the pump itself is dry. What's going on.
This is probably one of the most recurrent problems I see with Vortec engines, no matter the size. Careful inspect on the top front corners of the engine will show moisture where the intake manifold meets the cylinder heads. The area is usually hidden by the air conditioner compressor and alternator and is difficult to see. As the leak gets worse it will become very evident. Be assured, until it is repaired in will get worse over time.
The problem here is GM's use of plastic intake manifold gaskets. There were Tech Bulletins circulating in the mid 90's about the bolt torque settings being way too tight from the factory, resulting in the plastic cracking prematurely. The torque has been reduced, but it has only delayed the failure until the vehicle is out of warranty.
Early on in the failure, the coolant just seeps out. Eventually it runs out rapidly; sometimes even squirting over the grill. On rare occasions it leaks internally into the engine oil pan.
The fix is to remove the intake manifold and install a new gasket set. It is not a hard job, but the Vortec is a maze of plastic parts and connections. Some are fairly fragile and need to be handled with care. Take careful evaluation of your abilities before jumping in.
Here's one tip, if you do decide to tackle it. On most Vortec Engines the upper and lower halves of the manifold do not need to be separated for the lower gasket replacement. However, if the engine has high mileage, say above 120,000, it is smart to replace both the upper and lower gaskets.
Fel Pro makes a problem solver gasket that has a steel base instead of the OE plastic gaskets. They are a bit pricey at around $90.00 but they will never leak again if installed properly.
The Vortec is a great engine, but it does have some pattern failures that seem pretty common to them all.
Good luck and happy wrenching.