UFO Workhorse noise up front by driver.

[JimO]

Just checking, has anyone experienced a noise like a pump of some sort on a UFO chassis. It has always been there, but now it runs almost all the time. Its sounds like a small air compressor of sorts. When I open the front door that access the generator and window fluid it comes from the driver side above the access but I can's see anything. It is most likely right behind the cab wall near the dash. It only runs when I start the coach.

Thanks in advance!

[hwood13]

I've had the same noise, although not as consistently as yours. I've had it checked by authorized service centers and they can't find a thing!

[UFO Pilot]

Same noise with mine.

[BigGeorge]

I too get this pumping noise though mine is present only on starting and then seems to go away. Or, as the wife claims, I tend to go deaf to any continuous noise.

[UFO Pilot]

I never noticed mine until recently. It seems to go on and off as long as I am idling. Once I start moving it seems to go away.

[gbs2320]

I believe it is the power brake/abs compressor. Unlike cars that have a power brake booster that operates off engine vacuum ours like the buick grand national of old and my 89 jeep cherokee w. abs has a brake servo and abs pump that fills a (usually) ball shaped brake fluid pressure storage vessel. Mine pumps when I insert the key and turn on the dash like my old jeep. It will come on periodically to maintain required reserve pressure. When you are going down the road other noses keep you from hearing it. Greg

[cj5 jeeper]

It is a vaccume pump for the brakes, if the engine dies you may have armstrong steering, but you will still have brakes.

[gbs2320]

Quote:

Originally Posted by cj5 jeeper It is a vaccume pump for the brakes, if the engine dies you may have armstrong steering, but you will still have brakes.

I respectfully disagree. The vacuum pump behind the drivers side headlight is only for operation of the vacuum actuated controls on the dash ac/heat. If you look under the chassis above and behind the front axle drivers side you will see brake abs and pressure pump and abs control module with two ball shaped storage containers (one on each end). They store pressurized brake fluid not vacuum. With vacuum you would need a vacuum brake booster like on the cars and we have no such thing. When engine dies and all electric is gone we still have reserve pressure to stop with power brakes because of the reserve pressure vessels. These storage vessels are called accumulators and operate with nitrogen gas and brake fluid pumped in to become pressurized, much like pressurize small servo tanks on house well pump systems, I suppose. Greg

[JimO]

Sounds like you know what you are talking about. If it does control heater venting etc. do you think I may have a leak somewhere or is this running often like I am experiencing?

[gbs2320]

Quote:

Originally Posted by JimO Sounds like you know what you are talking about. If it does control heater venting etc. do you think I may have a leak somewhere or is this running often like I am experiencing?

You can tell whether it is the power brake pump or the HVAC vacuum pump by going to the two sources. Open the generator access/front hood of the coach and look behind the front drivers headlight. You will see the vacuum pump for the HVAC controls. Listen in that area for the noise and put your hand on the pump motor and feel for vibration. If that pump is not the source then do the same with the power brake pump it is under the coach above and behind the front axle on the drivers side.

If your vacuum pump keeps running check the vacuum line running from that pump to the small ball shaped storage vessel nearby and from that vessel to the HVAC controls for leaks or disconnects. Also check the storage vessel for leaks. You can spray soapy water and look for bubbles to locate leaks. If you have a leak you HVAC controls for your switching of heat and cold and air direction control (defrost, feet and face) probably are not working to some degree.

Your power brake pump should only run for the time it takes to pressurize its 2 ball shaped storage vessels (accumulators) (with your foot off the brake pedal). If it never stops running you need to take it in for service. Good Luck. Greg

[RocketDork]

Quote:

Originally Posted by gbs2320 You can spray soapy water and look for bubbles to locate leaks.

Does that work on a vacuum leak? It doesn't seem right.

On a car I used a propane torch (unlit) to find vacuum leaks, when the engine speed changes, there it is!

[gbs2320]

Quote:

Originally Posted by RocketDork Does that work on a vacuum leak? It doesn't seem right. On a car I used a propane torch (unlit) to find vacuum leaks, when the engine speed changes, there it is!

Probably not since it is pulling not pushing I guess. I usually use a vacuum gauge at each connection to trace a leak. Greg

[UFO Pilot]

Is this a Workhorse issue or a Coach builder issue? I was just denied warranty work on a Workhorse problem as the Coach builder did something that caused the problem.

[gbs2320]

Quote:

Originally Posted by wthomas1 Is this a Workhorse issue or a Coach builder issue? I was just denied warranty work on a Workhorse problem as the Coach builder did something that caused the problem.

Please tell us what the denied warranty work was and why they said the coach builder caused it. Many of us have your coach so we need the heads up on this. Hope you can get Winnebago to fix it. If the rest of us have the potential problem perhaps Winnebago would be more willing to help you when the rest of us similarly potentially affected start calling about this. Perhaps start at new thread on the subject. Good Luck Greg