Vacuum pumps on petrol engines.

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Hi all.

6 month ago we bought a 3 year old Toyota with a 1.6 valvematic engine. The engine runs great and is a really nice engine. But one thing bothered me..a lot. The engine had a faint but really noticeable knocking sound from the cylinderhead/valvetrain. It goes away above 1000 rpm's.

So.. I went to the dealer. They send out a mechanic he listened. And apparently it is perfectly normal. All Toyota valvematic engines do it. And the reason. A cam driven vacuum pump. He explained that due to the function of the valvematic system. The engine had no traditional throttlebody. And therefore no vacuum in the intake to support the brake system. Therefore they mounted a vacuum pump. Just like if it was a diesel. Or turbo engine.

It really does give the engine a bit rough idle sound. And not something I like to listen to.

But how normal is this to newer engine design. Any other engine makers who makes there engines like this? Or is it just Toyota?
 
You need to learn to live with it. Some newer engine designs are simply louder and it's for fuel economy and/or emissions. Mazdas Skyactiv engines are really loud when started on a cold day for the first minute.
 
Originally Posted By: shDK
....t due to the function of the valvematic system, The engine had no traditional throttlebody. And therefore no vacuum in the intake to support the brake system.

Any other engine makers who makes there engines like this?


Only other one I am aware of is BMW
 
On the Hyundai Genesis Coupe with the turbo and automatic transmission there is a vacuum pump for when the engine is in boost I guess.
 
I am pretty sure the Mazda Skyactiv engines do have a vacuum pump. They have a throttle body but they also have weird valve timing that lowers vacuum. So I have read anyway.
 
Will probably become more common. The only other way I know of to do a brake booster is to use hydraulics aka hydroboost, but that runs off the power steering pump which is pretty much dead these days now in favor of electric power steering.
 
My Ford EcoBoost 1.0 has a mechanical vacuum pump.

As does my 2008 MINI Cooper S. Actually, those have been known to seize. That's how I got a great deal on a used MINI. The exhaust cam mounted vacuum pump seized, which seized the exhaust cam, which sheared off the exhaust cam sprocket bolt and bent a couple exhaust valves.

I plan on replacing them preventatively ever 75,000 miles or so.
 
When the first level of save us from smog rules hit many car makers backed idle timing to zero advance or even AFTER TDC. This reduced idle vacuum to a very low level and VOLVO, for example, grafted a vacuum pump to the top of the valve cover. It was discovered by many that the pump could be removed and there would still be enough vacuum for brakes and HVAC switching. Cars have gone through many levelws of "anti smog" since and there's still smog in LA. Now they blame grills, lawn mowers, and motor bikes.
 
Originally Posted By: Colt45ws
Will probably become more common. ...
Yes, because manifold vacuum indicates wasted energy. Diesels, CVTs, Atkinson cycle engines, and the "valvematic" intake are all examples of ways to reduce the waste. Nothing says a mechanically or electrically driven vacuum pump has to be noisy, though.
 
Last edited:
Originally Posted By: CR94
Originally Posted By: Colt45ws
Will probably become more common. ...
Yes, because manifold vacuum indicates wasted energy. Diesels, CVTs, Atkinson cycle engines, and the "valvematic" intake are all examples of ways to reduce the waste. Nothing says a mechanically or electrically driven vacuum pump has to be noisy, though.


Well..to be fair the pump is noisy due til the pumping action. It is the air moving you can hear. Not a mechanical noise. If you place your ear on the air filter box. It is also clear to hear the air pumping.
 
They could've used a more expensive, quieter type of pump. Or could've muffled the existing one better, but that too would add cost, plus add weight, and take space. Fair trade-off or not? Automotive design involves numerous compromises.
 
Back in the '50's and '60's when Fords had vacuum wipers - full throttle and the wipers stopped. The English Zephyr had a vacuum pump combined with the fuel pump, so there was vacuum for the wipers even under low manifold vacuum. There is never annything new.
 
Originally Posted By: HerrStig
Now they blame grills, lawn mowers, and motor bikes.


Add cows to that list.
smile.gif
 
How about a return to non-servo brakes? I used to like them. Better brake feel, and made engine-off coasting on long descents much easier.
 
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