E450 brake noise

[dsurette]

2008 Coachmen Freelander 3150SS w/2007 Ford E450 making a strange noise when braking fairly hard. With light pressure there is no problem but there is noise kind of between a groan and a hum when applying more pressure to come to a stop. The noise continues sometimes for as long as about a minute after stopping and resuming driving. Even sitting idling the noise remains and eventually goes away. I think the frequency of the noise changes with engine RPM but I'm not sure.
We're at a s&b in Oquossoc, Maine and will be here for a few days before going back to Tennessee. I will have it looked at ASAP if I can find a place that can do the work. Anybody have any ideas about what might be going on so I can know what to expect? BTW it has about 40K miles on it.
TIA

[j-d]

I like the "drive in straight lines" part!

Must be what that part on the back of the AAA map's for...

[carringb]

Ford power steering fluid is MerconV but they renamed it so people would not substitute the MerconV SP or LV used the newer transmissions.

[dsurette]

I'll keep an eye on it and refill as necessary. Just need to get back to Tennessee where I will bring it to my regular service place. It will be due for an oil change and other regular maintenance by the time we get home. Until then I'll just drive in straight lines.

[j-d]

Glad to hear you found the source of the noise. Now, were'd the fluid go? The original fill of PS fluid usually lasts a VERY long time. We had an old C on Ford E350 and the pressure hose (pump discharge) developed a little pinhole. Engine off or simply running, didn't leak. Low speed steering and "dry steering" (turning the steering wheel without the coach in motion) and it would squirt a little fluid. 14 ounces is a lot of fluid for an ordinary PS setup, but I think it indicates a lead somewhere even in this bigger system.

[dsurette]

Problem solved. Thanks for all of your help.
As a side note, I went to the Ford dealer service department in Farmington ME and asked for Mercon ATF. They said Ford no longer makes that and that I'm supposed to use Motorcraft Power Steering fluid instead. I explained what I was going to use it for and they said that it is a replacement for Mercon V. Kind of confusing to me because I didn't ask for Mercon V but Mercon ATF. I guess they are the same.
Anyways, all is quiet with the breaking system again and I could find no leaks to explain the loss of fluid. It ended up taking about 14 ounces.
Thanks again for all the help.

[carringb]

ron.dittmer wrote:

I assumed the E450 power brake pump was it's own devise, not sharing the same fluid from the power steering pump and/or reservoir. I never had an opportunity to see underhood of an E450 to see how it was actually setup.

It's just a big loop powered by the power steering pump. It goes pump-->brake booster-->steering box-->reservoir-->pump except there's an extra return loop off the brake booster, and the brake booster has an accumulator to maintain pressure for a few brake applications if hydraulic pressure from the P/S pump is lost.

[ron_dittmer]

carringb knows his E-Series stuff.

I was about to say....

Unlike the E350 and a typical car with a vaccuum assist power brake booster, the E450 has a completely different hydraulic power brake system. Check that fluid, though you have brake fluid too.

I assumed the E450 power brake pump was it's own devise, not sharing the same fluid from the power steering pump and/or reservoir. I never had an opportunity to see underhood of an E450 to see how it was actually setup.

[hotbyte]

Good to know! Hope it resolves your noise and hope I can remember this if mine ever makes a noise 🙂

[dsurette]

Thanks Carringb. The PS fluid level is very low. We have to go into a bigger city (Farmington) and I'll get some MERCON ATF which Ford recommends. I'll post the results later, but I think you got it. Brake fluid is full.

[carringb]

Check your power steering fluid level. This is what powers your brake booster, and low PS fluid will cause it to suck air and make noise.

If its low, double check all your lines and make sure you don't have a hose rubbing anywhere or a leaking fitting. Also double check the brake fluid to make sure the booster isn't cross-contaminating.

[SuperDutyFiver]

Definitely sounds like the booster pump-I'm wondering if your booster pump is sucking some air when under load and it's taking a little time to purge it out after it's stressed?

[Queens_Carriage]

Have you checked your brake fluid? Just a place to start.

[dsurette]

Duplicate post. Sorry

[dsurette]

Yes, it continues with the brakes released and even while driving. I have turned the engine off and back on and the noise remains. But never much longer than about a minute. I agree that it is probably something with the power assist.