Hey folks,

Now to the forum but it has become a great help. I had the dreaded UIM failure today around midday. I am in hydrolock now. Should I rush to get the oil out and drain the coolant or can it wait until morning when I can get a floor jack and some jack stands?

96 Pontiac Bonneville 3.8L

I think you should be fine for a while as long as engine is not run.

You will want to get the fluids out as soon as possible. But waiting a bit until you can do it safely with a jack and stands should be ok.

Knowing how an engine works helps us understand part of the myth behind wanting to drain the fluids asap.

An upper intake failure fills the lower intake manifold with coolant that then travels into the cylinder causing hydrolock. The piston rings keep fuel and compression from entering the crankcase for the most part. They do the same with the water in the cylinder. Therefore removing the oil in the crankcase shouldn't be a critical issue.

The piston rod bearings may fail whether the UIM is fixed properly and the oil was drained asap, or they may not. My personal feeling and experience is this depends more on how many times someone tried to start the car with the cylinders hydrolocked. Reasoning for this is there is little to no oil between the crank and the bearing when the car is started. Because the water literally locks up the motor, the bearing takes all the brunt and potentially is hurt or marred by the starter trying to turn the motor when the piston can not compress the water to do so.

From the other side of the coin...some water may get past the rings. In my opinion and from what I have seen upon draining oil in a hydrolocked motor, the amount is either not visible or non-existant. Therefore the water would not have been pumped into the oil passages of the motor and the water could not hurt the bearings.

Backup to the theory above: Many people pull their valve cover cap and find moisture during season changes in the year. This is from condensation. In the above case...if the motor is run and no moisture is found on the VC cap or in the coloration of the oil that is drained, there should not be enough to support a theory that water caused the damage to the bearings. We do know that trying to start w/o oil in the bearings can cause damage, add hydrolocked to that and the bearings can potentially be harmed.