Car people help?

Question

My car occasionally makes this horrid kinda high pitch crunching/grinding noise but only when going up hill trying to speed up to the 80km/hr speed limit after being stuck behind a slow car doing 50km/hr. Got it serviced recently and the mechanic reckons the noise is something to do with the a/c, which just seems weird to me. Will have to book in with their a/c guy to figure it out and get it fixed $$$. I've been trying to make the noise happen every time I go over the hill to test the theory myself but of course, it doesn't happen when I want it to...

What's your opinion?

Anonymous · Accepted Answer

It sounds frustrating to have this mysterious noise, especially when the mechanic's guess about it being related to the A/C Based on the symptoms you've described, here are a few things to consider:
A/C Compressors: While it might seem weird, an A/C compressor can sometimes cause strange noises, especially when accelerating or under load (like going uphill). The A/C compressor works harder under these conditions, and if there's a problem, it can make grinding or squealing noises. The A/C might not be the root cause, but it’s worth checking. Transmission or Gear-Related Issues: The noise could also be related to the transmission or the clutch if you're driving a manual. If the car is struggling to shift smoothly or isn't engaging gears properly when accelerating uphill, it could cause a grinding sound. This is especially true if it happens when you try to accelerate after being stuck behind a slower vehicle. Brake Pads or Rotors: Sometimes, a grinding noise can come from the brakes, especially if they're worn out, or if something is caught in the brake components. However, since this only happens while accelerating uphill, this seems less likely, but it's still something to consider. Belts or Pulleys: Worn or loose belts and pulleys can also cause squealing or grinding noises, particularly under load, such as when accelerating uphill.

Since you're trying to recreate the issue and can't seem to get it to happen on demand, it could be that the problem only occurs under specific conditions (like load, speed, or engine temperature). It might be worth going back to the mechanic and asking for a more thorough inspection of the drivetrain or transmission, even if the A/C is a possibility.

In the meantime, if you suspect it might be A/C-related, it could be worth checking the refrigerant levels or ensuring the A/C compressor is functioning properly before spending a lot of money. Getting a second opinion from another mechanic who specializes in transmission or drivetrain might also be helpful if the issue persists.re-state://background_color_rgba (0, 0, 0, 0), font_color_rgb (77, 77, 77), justifyLeft, p

WindAtMyBack · Accepted Answer

High pitch and crunching/grinding don't go together. They are two different things, but they could be caused by a single problem.

Going uphill and accelerating means you are putting a LOT of load on the engine. So you are making the engine work hard.

The A/C can put additional load on the engine. The engine is working hard accelerating and going up hill. Then add to that the A/C.

It might not seem like the A/C should make much difference, but it does. A frozen compressor (A/C) can completely freeze the engine. There is a belt that connects the engine to the A/C. The engine is not just driving the wheels, but also the A/C and several other thing. If the A/C is not spinning freely, it can completely stop the engine from turning. If the A/C compressor is frozen you might not be able to even start the engine. So the A/C is not something trivial.

Some mechanics are better than others. They are often guessing. Even the best mechanics are guessing. But your mechanic has inspected the car and the "car people" here at GaG have not. The point is that the A/C MIGHT actually be the problem.

"Might" is the key word here. Most problems with cars can be caused by multiple things.

When you talk to your mechanic, pay close attention to the car. The more information you can give your mechanic the better.

Does the high pitch change with the RPM of the engine?
Does the high pitch change with the speed of the car?

The answer to those two questions is very important. It can help isolate the problem.

"but only when going up hill trying to speed up"

"Only" is one of the best words you can use when talking to a mechanic. It's good that you are paying attention.

Anonymous · Accepted Answer

Grinding could be anything and with the high pitch noise anywhere from your engine having metal chunks in it to yours transmission failing also what kind of vehicle what year what engine is in it people need more details to diag it

Kelly6 · Accepted Answer

@razp_sorbet does this noise only happens once after car was parked for longer, but doesn’t happen if you drove it lot?

BadApple69 · Answer

More details of the car itself would be helpful. Is it an automatic or a stick? Make and model car?
It could be the clutch on your AC making noise but that shouldn’t be affected by a hill…. But if you downshift and the RPMs are higher that might make the AC clutch act up. Not enough info to properly diagnose.

AviatorTom · Answer

My guess is that the AC compressor might need replacing, along with the belt that drives it, especially if the car is more than 5 years old. Before doing that thiugh, check that the AC system is fully charged with refrigerant. If refrigerant us low, the AC co pressure could make noise when running.

Finchie40 · Answer

The belt on your AC might be going bad and loosing it’s tension , so it’s more than likely wobbling when you have it on and driving uphill , so hopefully it’s just the belt that’s bad so they don’t rob you with money

MannMitAntworten · Answer

It might be the pulley bearing going out or the AC clutch. Take to a mechanic who does Air conditioners, double check. It could also just be your belt slipping which means you might just need a new belt.

FreyaRed · Answer

Most expensive will be AC compressor but maybe it's just a pulley or tensioner that costs few dollars. It's always good to have a car mechanic in your circle of acquaintances

DryGermanGuy · Answer

Has the mechanic checked specifically the belts and wheels around the climate system?

jshm2 · Answer

Sounds more like a brakes issue, not a/c issue.

exitseven · Answer

When it happens again try to shut the air conditioning off. See it the sound goes away or changes.

molonski2 · Answer

Sounds like the automatic transmission to me , kickin into gear.. not positive sadly.

Staximus · Answer

If it's the a\c then it won't happen when the a\c is off. I can't make a guess unless I hear the noise, plus different cars make different noises

Ariesman81 · Answer

What's it sound like? Like a whiiir whiiir noise or a knock knock knock noise?

Bklynbadboy12 · Answer

That's your transmission skipping you definitely have to take you car to a mechanic. Just a heads up transmissions are expensive to fix

msc545 · Answer

Does the car have an automatic or manual transmission?

Yellovv · Answer

What mechanic said to you when they do service?

kaucky1 · Answer

Clutch or transmission or car just not made sacred

wkhan_87 · Answer

Use best quality engine oil.

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