dayneger

Hello,

Recently I was driving my '04 RX-8 from the San Francisco area up to Lake Tahoe on a hot day and ran into a problem I haven't found described in the forum with search function.

Across the flats past Sacramento it was 110 degrees outside, with no problems. Heading into the mountains, the temperature slowly dropped to about 90 degrees when I passed 6'000 feet. I was driving reasonably close to the speed limit and all gauges looked totally fine the entire time.

All of a sudden I had a complete power loss--I went from effortlessly cruising uphill at 65 mph to having absolutely 0 power a second later; gas and shifting gears had no effect.

I pulled off on the shoulder while I still had some speed, tried a restart which failed, then waited a while. After about 10 minutes I tried a restart, which worked and got me to a nearby exit, where I decided to let the car cool down even more. Since then the car has been driving completely normally, with no recurrences.

Any idea of what happened, and how I can avoid it in the future? I've had my coils go before, but this felt very different.

Cheers!

Dayne

Grace_Excel

iTrader: (5)

110°, from the Bay to Sac'? About three hours before you got on the mountain in that condition could have caused your car to over heat. It could be a number of things and I can only think of two at the moment. Were you driving with the A/C during the whole trip? The temp gauge on our dash isn't that reliable, once that needle move a bar it is likely that the egine is close or have passed 220°. Which many would say "too high". Another theory is your fuel pump, how much fuel did you have in your tank as you were going uphill? Your pump could have over heated, the fuel in the tank helps cool down the pump, if you have at least less than a quarter in the tank would cause this.

Were you able to read any CEL, miles in your ignition systems and your engine? Once you're back in the Bay, have your compression and the CAT checked, as well.

Oville_rx8

I had a similar problem with mine cutting out with the same symptoms, turns out my water pump was leaking from the two breather holes on top and bottom. maybe give those a check.

dayneger

Sorry for the delay in responding--my computer went down and then I was out of the town. The interesting thing is that the problem occurred again.

Answers to the first questions: I tanked not far from Sacramento, so I had a full tank heading into the mountains. I did have the AC running the whole time, or I would've melted, but I spent no time idling at stop lights/etc. I didn't get the car into the shop to have the CEL read (it also didn't light up when problem happened). About 5k ago I had my compression checked and it was fine; at the same time I had the dealer decarb everything just to be sure. I redid plugs, wires and coils at about the same time.

I drove a similar route this last weekend to go backpacking with 2 others who were in the car, and as fate would have it the 4th of July was nearly as hot as the other day. Unfortunately my friends got treated to waiting by the side of the road for the car to cool down... twice!

After the original incident I rechecked my fluids and noticed that my oil was down about 3/4 quart from full, so I topped it off for the second trip to Tahoe. Otherwise the pattern was the same--reasonably full gas tank, AC running, climbing a grade (a bit slower this time), only got to about 3500 feet and suddenly a dead motor. 30 minutes later I restarted, driving in the low 50's on average, made it to 6000 ft before it died again. Waited 20 minutes, restarted, put the windows down and heater on high, drove no more than 40 mph on the climbs, and finally made it to Carson Pass. As a side note, every other car on the road seemed to be handling the conditions just fine.

Oh, another weird thing is that the cooling fans didn't turn on after the car died. When the car wasn't misbehaving, the fans would turn on/stay on when I parked and turned off the motor.

So, maybe a fuel pump issue? Any other thoughts? Is there any part of the electrical system that will totally turn the car off when it gets hot (and if so, why is the car overheating)?

Thanks!

RIWWP

iTrader: (2)

The car won't suddenly shut off, and then allow a later restart, if it is an overheating problem. If the coolant overheats enough to suddenly shut the car off it will never ever re-fire for any reason.

This totally sounds like a fuel pump failure. The fuel pump builds up heat until it shuts down. It cools off over time and allows you to start up again after it's cooled far enough.

Replace the fuel pump.

dayneger

Thanks for the help here!

Ok, so a fuel pump failure is the likeliest cause, and maybe a water pump.

For the water pump possibility, I would be losing coolant from the radiator, right? As far as I can tell, the level has remained constant, so I'm guessing the water pump is ok.

For the fuel pump, would that also trigger a mode where the cooling fans wouldn't run after the cutout occurred?

In any case, I did a quick search here and online, resulting in my probably being more confused than before. There's a full OEM assembly available on Mazmart for $323, Airtex units available for about $190, and BHR has both Arram replacement motors for $75 and Walbro performance pumps for $110.

I don't have the tools to replace this myself, so I'd have to have a shop do the work. Which option would you recommend? And do I need a Mazda dealer for the job, or could a non-specialist shop I've used before do the repair?

Cheers!

D.

RIWWP

iTrader: (2)

This isn't a water pump problem. At least, if it was you would be listing other symptoms instead. Running with the heater on high, the lack of coolant loss, no coolant smoke, no seized engine... all this tells me that this wasn't caused by a cooling system failure. And none of those things affects the temperature of the fuel pump. The only thing that affects the temperature of a failing fuel pump is immersion level (a weak pump might fail easier with low fuel levels), distance driven since starting, amount of overall engine load, how long it has to cool off after it fails, etc... You hit all of these points fairly well I think.

The cheaper options are probably the pump itself, with no assembly, the more expensive is probably the pump plus assembly. Separating the two requires special tools. Most shops should have them, but not really sure about that. The assembly should drop in with simple common tools.

Any shop should be able to do it cheaper than the dealer. The fuel pump is easily accessible under the rear seat behind the driver.



I don't place much weight on the cooling fan status. They aren't always on, there is logic behind it, and it could simply be that you triggered logic that shuts them down immediately. You can do it with a normal shut-off too.

monchie

This could be my problem specially when the weather is so hot...

I might have to check on that...