I have a '95 XJS. It was the end of 20 years of that model, and Jag still did not fix many of the design problems on my car that were apparent on the very first 1976 XJS. Whatever is happening here, it is not common, but rather a very occasional alignment of circumstances.

I am very curious to hear how much water it takes to lock up the engine...my feeling is it may only be a dribble. If it were a lot, it would freeze and crack the cylinders. Apparently that did not happen.

 

I did some digging to see if there is some precedent with this type of issue. I found nothing for Jag but there appears to be a fairly common problem with Ford trucks equipped with the eco-boost engine.

Intercooler Condensation buildup - Ford Truck Enthusiasts Forums

It is important to note that this is a turbocharged and not supercharged engine which is a BIG game changer. It seems also that the issue only happens in humid climates with the vehicle held at a steady state cruise over an extended period. The intercooler apparently 'chokes' on accumulated water reducing engine power due to restricted airflow.

It's easy to say 'a compressor is a compressor' which is true in isolation, but the type of compressor also dictates how much air is compressed to what degree under what conditions. A turbocharger only produces boost 'on demand' and roughly in proportion to exhaust heat and flow. Under light load conditions, such as highway driving with cruise selected, there is little or no boost being produced and therefore no significant heat added to the air. Routing this air through a cooler could then have the effect of having moisture condense and collect as seen on the Fords. Apparently the problem can be cleared by heavy application of throttle which increases both the velocity and temperature of the air in the intercooler causing the water be vaporized and pushed harmlessly through the engine.

Superchargers on the other hand are 'always on' and produce boost in rough proportion to engine speed. They essentially never get to just idle like a turbocharger and as such, there's always sufficient heat and flow to keep the intercooler passages clear.

Another important point is the OP lives in Michigan. Winter air, as anyone here in the frozen north can attest is agonizingly dry. The amount of moisture in the air during the winter up here is roughly equivalent to a warm Texas day with 15% relative humidity. IOW- never happens.

No matter how I try to determine why the OP's car ended up with water in the cylinders, I cannot explain water in the intercooler migrating to the engine after shut down. If it entered while running the engine would hydrolock. If it sat 'waiting' in the intercooler, it would have frozen and an effect similar to the Ford trucks would been observed.

 

The volume of water required to hydrolock a cylinder is equivalent to that of the combustion chamber with the piston at TDC.

 

Thx to all of you for sharing these views on this apparently rare case of design flaw. The physics/engineering skills and ideas of some of you are really very useful to sort the issue out and it is in such a lively and technical forum that we can understand what may happen and how to address it.
I am still puzzled that after decades of design of engines and race testing in all conditions this kind of issue still may be revealed for normal driving, needing further design improvements!
Cheers,

Serge

 

I think it didn't do what he's been told. It's never been observed and is implausible. The frozen starter is a known but rare thing on these very cars (well, an STR, but same setup essentially).

 

Mikey, you are forgetting the throttle plate. The supercharger always turns, but at normal cruise it produces no boost. The entire intake track is below atmospheric pressure at idle and normal cruise.

Here is yet another example. The exhaust is always much hotter than the intercooler, but on a cool morning the exhaust pipe spits water. The explanation is that the exhaust is not that hot at initial start up, so water condenses in the cool pipes. Likewise, the intercooler on this car is very cold on initial start.

What you found pretty much confirmed that condensation in an intercooler is, indeed, possible...and, I was right about reving the engine being a preventative. Our supercharger always turns, but at part throttle (steady cruise) the engine vacuum is sucking harder than the charger is pumping...so there is little or no load on the charger.

I agree with you completely what hydrolock is and how much water it takes. I am not sure this was hydrolock, though. If it was, the amount of water would have cracked the cylinders when it froze and expanded. I think we are dealing with a small amount that froze and "glued" the rings in the cylinder bore. But we will see which is was when he gets answers from his mechanic.

I love these posts that make us think...!

 

Except for two critical points

1) the ambient temp was below freezing. Any water collected in the intercooler while the car was stopped would be ice.

2) the engine would not turn over at all. Irrespective of whether there was water or ice in the intercooler- it could not have been drawn into the cylinders.

Back to square one.

Edit: the volume of water sitting in the cylinder(s) was sufficient to prevent the engine turning over even after the car had thawed out over a 2 day period inside agarage, not a just case of rings freezing to the cylinder walls from some moisture.

 

The exhaust is a tough one to argue because an engine creates lots of water that wasn't in the incoming air. You could have zero water in the air, zero in the intakes and you'd be bound still to get the exhaust behaviour.

Reason: burning hydrocarbons. HxCy + O2 -> H2O etc

 

I was finally able to speak directly to the mechanic today, and asked him the questions I outlined in my above post. He couldn't tell me exactly how much water was in each cylinder, as the method to extract it was to remove all the spark plugs and turn the engine over (self purge he called it). When pressed, he estimated an ounce or less in each cylinder. He did feel that the little amount of water was enough to prevent the engine from turning over, thinking that the piston was in it's compression stroke, and because the water wouldn't compress (like air), it kept the engine from rotating.

As to the cause, he did not have a solid explanation, but his theory was that the intercooler may have had water/moisture that had froze, and when the engine shut off, the heat from the engine allow the water to melt, possibly draining into the #3 and #6 cylinder. As the entire engine cooled during the day, the water eventually froze again in the cylinder. He indicated that my auxiliary water pump was bad (not the s/c pump), and that without that additional circulation help, it may have contributed to the situation. (Hopefully this will fix my cool heat problem Link)

As to stop it from happening again, he suggested I get the aux water pump fixed, but also to let the engine idle for a minute before shutting it down. I asked if it would make more sense to "punch it" to clear out any potential moisture, and he thought that may be a good idea as well.

 

I hate "punching" my motor just before shutdown, probably a hangover from my turbo Datsun Z days.

 

I believe the intake tract is higher than the intercooler- water cannot defy gravity.

 

Then how do rain showers happen?

The facts are:

1) Water got past a dry air filter into a completely sealed intake tract.
2) It wound up in the cylinders.
3) It was NOT orange antifreeze or washer fluid.

If you can come up with any explanation for this "magic" other than condensation...then you are much smarter than I. Take the argument up with the man upstairs who set the rules. I give up.

Quickcat...I'm glad to hear you got it all resolved. I, for one, really enjoyed the post and learned a lot.

 

(?) They obey gravity too.

Maybe you could rationalize the mechanic's logic of associating the aux coolant pump with the locked engine. That one baffles me too.

 

How's all that rain water get in the sky to begin with? What lifted all the water from the oceans to fill your Great Lakes, which are way above sea level? Our lives depend on water defying gravity.

It seems Quikcat's mechanic understands condensation. He is thinking that circulating more heat may reduce the ... condensation.

 

Water vapour is lighter than air, hence clouds. No defiance.

 

Precisely!

 

So now the theory is that despite the extremely dry winter air and sub freezing ambient temps, water trapped in the intercooler was heated by residual engine heat first evaporated, travelled along the intake tract, and subsequently recondensed in sufficient quantity in two cylinders of a still hot engine to cause them to hydrolock.

Right.

 

Mikey, I understand that it sounds unlikely. But instead of continually bagging on me, how about offering some constructive idea? I have completely gotten the point you don't like the condensation theory, but you have yet to offer any other option at all.

 

I think the villain in this saga is the mechanic(s) who have fed the OP three different fairy tales that make no sense. None of us were at the scene of the crime and the evidence is long gone.

There's no precedent I can find of such an event happening on any other Jag. I had a tough time finding any examples of waterlogged intercoolers on any vehicle. The ones I did find all involved critical weather conditions that did not exist in the OP's case nor were the engine operating conditions similar.

Trying to guess 'who done it' via third handed info is pretty futile but making leaps of logic that defy laws of physics does more harm than good.