Big thanks to Steve and his Real Gauge invention, it saved me from almost certain doom.

I took the car in for a few dyno pulls this morning. Everything was fine and normal on the way there, temps right at 200F the whole way. Even during the runs, temp went up a little, but not outside what you might expect after a few hard pulls. The tech took the car outside and parked it.

When I got in a few minute later to leave, I noticed the temp was above normal, something I never would have known without Real Gauge. I thought it might be heat soak, so I ease off into the street keeping one eye on the gauge, expecting it to start moving down as I get a little air moving throuh the radiator.

It doesn't! Keeps climbing toward the danger zone. Real Gauge let me see all this happening, so I quickly turn off into a parking lot, the temp alarm starts beeping and I shut the car off, coasting into a parking space with the fans whirring away.

Let the car sit for a while and cool down. Check the water level, no problems there. Strange, I think.

Start it up, and let it idle a minute. Nothing unusual, still below operating temp. Move gently out onto the street again, one eye glued to the temp gauge as it starts to climb. Almost to the highway on ramp when it passes the normal level again. I veer off, and find another parking lot to pull into. Call the roll back, and have the car delivered to my garage.

If not for Real Gauge and being able to see what was happening I surely would have started onto the highway before the standard "idiot light" temp gauge have even bothered to tell me that anything at all was wrong.

Thanks Steve, for creating this useful tool.

And if you ever need a good upper body workout, I highly recommend low speed maneuvering in an X100, without the power steering.


P.S. The thermostat, is only ~1.5yrs old, and everything was working normally on the drive there so I don't think it stuck. My suspicion is that during the last run on the dyno, the water pump impeller gave up. The odd part is that I had replaced it not but a few thousand miles ago as preventive maintenance. I won't know for sure until I pull it out but I think I'll replace both just for safety sake.

 

Sounds like you avoided disaster. Always a good thing.

I'm a big fan of the RealGauge as well. No Jag should be without one.

 

Hopefully not the impeller....if it is make sure you find all the pieces you can that may clog your engine passages.

 

Do you suppose that perhaps the lower radiator hose collapsed from high suction during the dyno runs and now collapses too easily? Just a suggestion if nothing else seems to be the culprit.

 

So... what was the horsepower?!

=)

 

It's a good thought.

I don't see anything that obviously suggests a collapsing hose, but I'll keep a watch for it.

 

Why am I not surprised you're the one who asked that?

Ok, so the caveats first. There have been fewer 4.2 cars done up with a twin screw kit and mine isn't entirely sorted out yet. Avos has been helping me to figure out the details and this dyno pull's MAIN purpose was to collect some Air/Fuel data to figure out an optimized MAF calibration.

Test Environment:
It's Too lean: that's been my problem and what we are trying to sort out

It's too hot: it was 90F today, which is higher than ideal and about 35F higher than my baseline run.

No water/meth: because I'm trying to figure out the true fuel ratios all of the pulls were done without the water/meth injection, which I suspect would have helped considerably

All the excuses out of the way: She made 421hp at the rear wheels.

With just the twin screw.

No sport cats, no fancy exhaust, no water injection, no nothin extra. And it was lean of the best power ratio.

 

Hope ya didn't hurt the head gaskets.......

 

If he shut it off within a few seconds of hearing the RealGauge audible alarm, I am pretty confident there is no damage.

 

Good power and i am keen on this real gauge thing, off to search.

 

The Real Gauge has an audible alarm?!! probably good that I haven't heard it..

 

It sure does...and it will definitely get your attention. BTW, it can be silenced (until the car is restarted) by holding in the button on the end of the blinker stalk for about 2 seconds.

 

Steve please make us a RealGauge for the X350!

 

I hope to do one for most other late models Jags eventually, but the S-type will probably be next in line.

 

'05 BMW 3 series also..............I'll bet the list of dumb gauges goes on and on. This could be big!!!!

 

CC - sorry to hear of your issues, but hopefully by the sounds of things you caught it just in time, thanks to Realgauge.

Hope to hear all is well...

 

Thanks.

I can see the positive side though, at least it failed in a controlled environment, 8 miles from home rather than on a long trip far away.

Shouldn't be too hard to diagnose and fix, there are only a couple of things it could be.

 

Pulled apart the cooling system today to figure out the overheating problem. Not too bad a job, and it was the water pump as I suspected.

There is a hairline crack in the impeller that lets it spin on the shaft. Looks perfectly fine at first glance. I have to imagine this is just a manufacturing defect that I didn't notice when I installed it.


Replaced it with a Beck Arnley metal impeller one this time, and also replaced the thermostat and radiator cap for good measure.

On a quick spin around town, the car is back to it's normal behavior, running right at 200F. No water in the oil, no oil in the coolant when I drained it, no steam coming out of the exhaust. So far so good.

 

What brand is the one that failed?

 

It is an ACDelco brand.