Loss of brakes

[MCNPathfinder]

Hey all, I have a question for all of you. My truck is at the dealership again for transmission issues. They of course didn't find anything wrong with it like normal. However, I asked them to also take a look at my brakes. Whenever I pull anything, I seem to lose brake pressure. I have two boats that I pulled around last summer. One collectively with the trailer is probably 800-1000 pounds? The other with the trailer is probably pretty close to 3800-4000 pounds. It wouldn't happen so much with the small one, but often times I'd be driving down the freeway clocking along at normal speeds and I would go to start applying the brakes for an exit ramp and the pedal would go to the floor, and I'd have to pump the brakes to get anything. Same thing for my larger boat of course I never took it on the freeway. The service manager at the dealership said if the load is close to 1000 pounds, I should really be using brakes on the trailer because the brakes are getting too hot. Which makes sense because when the car is given time to cool down, I don't have problems. I just kind of wanted to get another opinion, just in case. Neither of the trailers have brakes, although I had already planned on putting brakes on the big one because it needs it. That explanation just seemed a little odd because I would think that pulling a 1000 pound load down the freeway at 70MPH and not using the brakes for at least 10 miles of freeway driving would have kept them cool. I don't know a whole lot about cars really, but that's what the forums are for right? My truck can hardly tell there's a load on it with the small boat, the big one is a different story. LOL!

[Towncivilian]

When was the last time you had your brakes bled? If the brake fluid boils, the pedal will go to the floor. Brake fluid is hygroscopic, meaning it absorbs moisture from the atmosphere. This lowers its boiling point. If you haven't had a brake flush in a while, get one! Use DOT4 or DOT5.1 fluid for higher minimum wet and dry boiling points. If you have a 4WD Pathfinder, ensure the load sensing valve gets bled as well. See this thread, "Brakes" section for some more information about brake fluid.

Since you tow frequently, perhaps you should install an auxiliary transmission cooler in-line with the stock cooler; this may help alleviate your transmission issues.

[MCNPathfinder]

Sweet! Thanks for the help! I think I'll probably add a transmission cooler too. Seems like a good idea. I've never flushed the brakes, and I've owned the car for almost 2 years. Thanks again for the help!

[Towncivilian]

You're quite welcome.

You can get this 20,500 BTU rated stacked plate cooler for $58 before tax if you order online, use discount code VISA, and pick-up in store. I run a smaller version (a 13,000 BTU) on my Pathfinder with no issue. I suggest the installation of a Magnefine in-line filter (3/8") on the cooler return line as well. You may need to purchase some additional transmission cooler line hose (don't use cheapo fuel line hose). Here are some awful pictures of how I routed my hoses:







In the first picture, the hose on the right has the original short hose (from below the vehicle) leading to one end of the Magnefine which is tucked behind the bumper, then has a 4 foot hose leading to the return fitting below the vehicle. The hose on the left is from the stock cooler outlet to the auxiliary cooler. The other two pictures should hopefully make enough sense of how I routed the hoses otherwise.

[MCNPathfinder]

Awesome! Thanks so much for the write-up. Do you think my warranty company would throw a fit if I DIY'ed it in there? Or do you think they would prefer to have a professional have installed it? I'm kind of banking on them replacing the transmission while it's in the dealership. I'd hate to screw with any sort of warranty I might have on the new one or my existing warranty. Thanks again!

[Towncivilian]

That I am not too sure about. Your best bet would be to call the warranty company and ask.

I know the Magnefine was given a Ford part number and specified to be used after a transmission rebuild to reduce contaminants from the rebuild process (thereby reducing failure rates and irate customers) - but this fell out of practice for some reason, though that likely doesn't have any impact on a potential warranty breach on your Pathfinder.