rkuo

Hi all,

Bought a fixer upper Boxster and am going over it for things that need replacing. In addition to a few usual things, one thing I've noticed is that there seems to be an RPM related whine coming from the front of the car. Any clues on what could be the cause?

aron in toronto

If it's a "Coke bottle" sound coming from the front passenger side near the gas tank it may be a faulty fuel tank EVAP shut off valve.

link:
https://rennlist.com/forums/996-foru...VAP+shut+valve

&
https://rennlist.com/forums/996-foru...ht=coke+bottle

Macster

Trying hard to thing of something driven at engine speed at the front of the car. Can't think of anything.

All accessory drives are of course on the front of the engine which is right behind the engine access panel behind the seats.

There are 2 electric fans, one each corner located just ahead of the front wheel wells. These come on when 1) coolant temperature climbs above 212F; 2) A/C compressor is turned on. They switch to high if coolant temperature climbs to over 216F. They switch off when coolant temperature drops to 205F.

You'll need an OBD scan tool to view OBD data -- coolant temperature among the data -- to know the actual coolant temperature cause the in-dash temp gage is mostly there for show.

There's fuel pump located in the gas tank which is located under the front the car behind the front trunk and ahead of the cabin.

Then there are numerous water hoses and hydraulic hoses to feed coolant water to the radiators and of course return it to the engine and to feed hydraulic oil to the steering rack. These are of course fed fluid by accessory drives that follow engine rpm. Could be air in a line or a loose, improperly routed line is humming/buzzing and causing the noise.

It is very common for an older Boxster to have been worked on by someone who didn't know what he was doing and thus had its bumper cover removed along with other hardware and this bumper and hardware improperly re-installed.

Also, if the car suffered any accident damage it is likely coolant or hydraulic hoses not fastened securely or routed incorrectly. (Another "gotcha" is the fan resistors are not mounted properly but jammed in between plastic panels and held in place by friction. These run hot and this is not good for them or the plastic they're sandwiched inbetween.) Body shops are noted for not doing mechanical work properly wiring/hoses/etc get put back together all wrong. The connections are right, but the routing wrong. The securing of the hoses/lines/etc are wrong.

Sincerely,

Macster.

THXBABE

Wheel bearings?

rkuo

Thanks guys ... working on the brakes at the moment ... will dig into this one afterwards!

sjfehr

Whining coming from the front end? Can't hear it when the engine's revved up to high RPM? I hate to say it, but I think it's time to let your wife out of the trunk. Be prepared for even worse whining, though.

rkuo

OK, I messed with this a bit more. The noise goes away when I shut off the A/C. What's that mean ... bad compressor or fan? I *think* that it's passenger side.

Macster

When the AC compressor on -- the snowflake symbol lit -- the radiator fans should be on at least low speed. (They can be on high speed under extreme conditions like if the engine coolant temperature is elevated or there is some signal of extreme cooling demand from the A/C system.)

Now of course the fans are on and the compressor is operating as well, but the fans are located just ahead of hte front wheels while the compressor's located at the front of the engine behind the cabin's rear wall.

There's another "test" you can do: Shut off the AC. Drive the car and get it nice a hot. No need to beat on it just drive it normally in mild/warm weather. City driving does it for me.

With the engine idling allow the coolant temperature to rise until the radiator fans come on low speed. They should come on when the coolant reaches 212F degs. Be sure both fans come on. Check for air flow into the duct opening and air flow at the exit under the car just ahead of the front wheel well.

Since the A/C compressor not running any noise you hear from the front has to arise from the fans.

If the noise present not the A/C compressor. If not present while it may not be the A/C compressor it might be something to do with the refrigerant being pumped through the condensors. One is loose, has a broken bracket, or a pinched line or something that is causing the refrigerant to make a noise as it passes through the lines and condensors.

Sincerely,

Macster.

rkuo

I'm pretty sure I've heard the radiator fans kick in on high whenever I get home from work and I'm circling in the parking garage looking for a spot and it's unrelated to the whine. I'm gonna have to open up the car and listen more closely with the AC on. Oh well, nothing's dead yet, but not a lot of good online instructions for replacing the compressor if it comes down to it. This isn't going to require me to get under the car, is it?

minnesota911

You are low on air conditioning coolant " R-134 the "coke bottle noise is the valve without enough coolant and the whine is a noise it makes when it is low. Grab a gauge and plug it into the LOW tap on the passenger side engine compartment. add until it is up in the green. I have had 3 boxsters and each one did exactly the same thing and that was always the answer. cheers!

paulofto

Minnesota911, you do realize you are responding to a 9 year old post? RKUO likely has fixed it or sold the car by now.