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Estremo

Noise from engine - disappears with belt off

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After a longer trip my Boxster S 986 2000 started to have a very unpleasant sound. I didn’t here it while driving until I started to drive very slowly and that still is the case. It can be heared while the car is stationary or at low speed. After that the sound is eaten up by road and other engine sound. It was a long trip on the motorway in temperatures that is very high, in nordic climate measurements at least.
 
I’m having a hard time describing the sound, especially since English isn’t my main language, but I think it sounds a little bit like a truck sound and as if the sound is from something moving/rotating with kind of a scraping/not smooth sound. I hope these sound files and video clips will do a better job than me trying to explain.
 
The sound isn’t there when the car is cold and it starts after a couple of minutes. I feel like it also increases with rpm.
 
 
 
From within the car with the shield and interior on in front of the engine:
 
I took of the belt and then the sound disappeared completely. The belt itself, which I changed last year, looks good. I also mounted my old belt and the noice was still there. This got me down to three theories:
 
Water pump
The water pump can be moved inwards/outwards, is this how you would know that it should be changed? I think it can be moved from a couple of mm to half a cm maybe. It doesn’t make any sounds when I spin it. No other signs of it being bad. The water level in the trunk have been exactly the same for years and the temperature is fine. I don’t know if something of interest can be heard or seen from this:
 
AC compressor
This can also be moved inwards/outwards slightly and it does make a little scraping sound when I spin it. The mic didn’t really pic it up good so you have the turn the sound up quite a bit but than it could be heard rather clearly. The AC cools as it should and the sound doesn’t change wether the AC is turned off or on:
 
Crankshaft
When the belt is off it makes a very clunky noice that to my ears doesn’t seem right. Kind of like it’s wobbling. I think it can be heared quite clearly here:
 
Can it from this be said what the problem can possibly be, out of these three or do you have another theory maybe? All help is greatly appreciated! Right now I don’t now what I should do and if I can drive it to a mechanic or if I can find the right source of the sound and change it myself without moving the car.
 
Don’t now if this needs to be said since the sounds disappear when taking the belt of but I have reinstalled all the spark plugs (none were loose) and checked the heat shields. Some of the spark coils had cracks/missing pieces in the plastic but I guess that doesn’t affect their function?

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Posted (edited)

The only piece of advice that I can give is not to drive your car until you know how serious the problem is.

My first step would be to remove the oil filter, sift the oil which is in the bottom of the filter canister and cut open the filter itself to inspect if there are any ferrous particles in particular in there which obviously should not be there.

 

P.S. You don't need to drain the oil from the sump ... just remove the filter.

Edited by wizard
Additional P.S.

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Posted (edited)

How about the alternator, the steering pump and all the pulleys when you hand spin them?

Edited by Ahsai

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9 hours ago, Ahsai said:

How about the alternator, the steering pump and all the pulleys when you hand spin them?

 

12 hours ago, wizard said:

The only piece of advice that I can give is not to drive your car until you know how serious the problem is.

My first step would be to remove the oil filter, sift the oil which is in the bottom of the filter canister and cut open the filter itself to inspect if there are any ferrous particles in particular in there which obviously should not be there.

 

P.S. You don't need to drain the oil from the sump ... just remove the filter.

 

Thank you for the advice. I guess I wouldn't find anything unusual there if it's the water pump or AC compressor that is making the noice? A good clue that it's something else if I find something though.

 

9 hours ago, Ahsai said:

How about the alternator, the steering pump and all the pulleys when you hand spin them?

 

I would say that everything else sounds normal. The only wheel that sounds wrong when hand spinning it is the AC compressor with it's slightly scraping sound. Do anyone know if all the other wheels are on the same place on the non AC version so I can buy a belt for a Boxster without AC and see if the sound disappears when the AC isn't spinning?

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My advice was based on the "wobbly crankshaft" scenario.

 

I hope that it is (only) a duff aircon compressor.

 

Let us know what the problem is  ... and good luck.

 

 

 

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The a/c compressor should not feel scratchy but I'm not sure if it's enough to make the unpleasant sound you described.

 

Since you mentioned you can hear the noise when the car is stationary, you can use a mechanical stepthoscope to check the a/c compressor pulley (the clutch is stationary when the a/c is off) by touching the probe on the pulley. Obviously, be very careful though with all the moving engine parts.

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3 hours ago, wizard said:

My advice was based on the "wobbly crankshaft" scenario.

 

I hope that it is (only) a duff aircon compressor.

 

Let us know what the problem is  ... and good luck.

 

 

 

Yes that is a very good point and the crankshaft is what concerns me the most. I will just have to decide in what end I should start. Thank you!

 

2 hours ago, Ahsai said:

The a/c compressor should not feel scratchy but I'm not sure if it's enough to make the unpleasant sound you described.

 

Since you mentioned you can hear the noise when the car is stationary, you can use a mechanical stepthoscope to check the a/c compressor pulley (the clutch is stationary when the a/c is off) by touching the probe on the pulley. Obviously, be very careful though with all the moving engine parts.

Another great tip! I will make a little list of things to order to get this going since my nearest (which is still far away) Porsche center had a months waiting time to get it fixed. At least a new water pump is on the list since it seems to be due for a change no matter if it's whats causing the noice now or not.

 

I'm still very open for new ideas or if anobody recognize the noice or now if the crankshaft sound is normal or not.

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For some reason I missed some of your video clips till now. The crank pulley doesn't look wobbly to me. However, that pinging sound is not good and I can't tell what it is because it doesn't sound like lifter or bore scoring to me. It does follow the rpm directly so it's something reciprocating internal of the engine.

 

Your water pump needs replacement for sure and the a/c compressor clutch is not too bad. I would definitely try to track down that pinging sound first (by using a stethoscope carefully) with the drive belt off the engine.

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Also check if that pinging sound is from one of the catalytic converters (loose element inside) and all the spark plugs are tight.

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22 hours ago, Ahsai said:

For some reason I missed some of your video clips till now. The crank pulley doesn't look wobbly to me. However, that pinging sound is not good and I can't tell what it is because it doesn't sound like lifter or bore scoring to me. It does follow the rpm directly so it's something reciprocating internal of the engine.

 

Your water pump needs replacement for sure and the a/c compressor clutch is not too bad. I would definitely try to track down that pinging sound first (by using a stethoscope carefully) with the drive belt off the engine.

That's exactly the kind of comments I was hoping for, great!

 

It isn't wobbly, it was just a way of describing the sound. But ok, then I'm not the only one that thinks that sound is scary.

 

I will buy a stethoscope but what should I do with it with the belt off? Just put it against different places of the engine? It can't be heard at all when the belt on so my feeling is that the pulley is making the sound when the belt doesn't hold it place, or something like that.

 

Will also order a new waterpump and a thermostat while I'm at it.

22 hours ago, Ahsai said:

Also check if that pinging sound is from one of the catalytic converters (loose element inside) and all the spark plugs are tight.

Wouldn't make that sound no matter if the belt is on or off it was catalytic converters? I have tighten all the spark plugs and they were ok.

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With the belt off, you use the stethoscope (a simple mechanical $10 one will suffice) to trace where the noise is coming from by touching the suspicious areas. Check out the video of how to use one here.

 

When the belt is off, the idle load on the engine is much less and that may make a difference in terms of generating noise. No need to guess anyway, just use the stethoscope to  probe different places of the engine until you locate the source of the noise.

 

 

 

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Posted (edited)

I recently chased down a noise on my '98 986.  

 

With the belt off the noise went away.  Every thing like rollers, water pump, alternator all spinned freely.  With the belt back on and a $10 stethoscope from "Harbor Freight" , I deduced that the noise was coming from the alternator's front bearing.  I took it to a local auto electrical shop and had it rebuilt for $125.  Problem solved.  

 

 

Edited by kbrandsma

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On 7/31/2018 at 10:18 PM, Ahsai said:

With the belt off, you use the stethoscope (a simple mechanical $10 one will suffice) to trace where the noise is coming from by touching the suspicious areas. Check out the video of how to use one here.

 

When the belt is off, the idle load on the engine is much less and that may make a difference in terms of generating noise. No need to guess anyway, just use the stethoscope to  probe different places of the engine until you locate the source of the noise.

 

 

 

Good point about the engine load. That makes sence.

 

I'm away at the moment but listen with a stethoscope is the first thing I'll do when I'm home again. An electrical seems good in the sence that I could use sound isolated earphones, but maybe the outside noice doesn't disturb that much wich a mechanical one.

 

I came to think about an earliear question about tightening the spark plugs. Would a bad coil possibly produce the same sound as a loose spark plug?

On 8/1/2018 at 2:22 AM, kbrandsma said:

I recently chased down a noise on my '98 986.  

 

With the belt off the noise went away.  Every thing like rollers, water pump, alternator all spinned freely.  With the belt back on and a $10 stethoscope from "Harbor Freight" , I deduced that the noise was coming from the alternator's front bearing.  I took it to a local auto electrical shop and had it rebuilt for $125.  Problem solved.  

 

 

That gives me great hope, thanks!

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It's unlike a coil unless you also get a CEL with P03xx codes.

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I tried spraying some WD-40 behind the belt pulley on the alternator and the sound instantly improved but soon returned.  I decided to replace it rather than put everything back together only having to redo it later on.

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On 7/31/2018 at 10:18 PM, Ahsai said:

With the belt off, you use the stethoscope (a simple mechanical $10 one will suffice) to trace where the noise is coming from by touching the suspicious areas. Check out the video of how to use one here.

 

When the belt is off, the idle load on the engine is much less and that may make a difference in terms of generating noise. No need to guess anyway, just use the stethoscope to  probe different places of the engine until you locate the source of the noise.

 

 

I'm  back home again and with a new stethoscope but it wasn't as easy to track down as I would have hoped. What I missed last time however is that two out of three rollers are making some sounds that I don't think they should. As I understand it they should be quiet so I probably should replace them anyway. Is it possible that they would make noises like this when they are going bad?

 

I started replacing the water pump also and found green coolant, was this color ever used in the 986? I bought two litres of Porsche coolant since my Porsche center said that it's what I need to refill after replacing the water pump. They didn't changed the coolant so I thought that neither should I, but now I'm not sure if I should flush it completely while doing this work or if I should just fill it up?

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The original coolant in early 986 Boxsters was green and was superseded by pink years ago.  While the pink is backwards compatible with the green, I would dump the entire system and start with a fresh 50/50 mix with distilled water for maximum protection and life expectancy.

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4 minutes ago, JFP in PA said:

The original coolant in early 986 Boxsters was green and was superseded by pink years ago.  While the pink is backwards compatible with the green, I would dump the entire system and start with a fresh 50/50 mix with distilled water for maximum protection and life expectancy.

Thank you, then I guess I probably have the original. Would you just dump it as getting everything it all out and then refilling it with new coolant or also flush it completely with distilled water once before refilling it with new coolant?

 

Does it really matter if I change the water pump and thermostat before refilling? Thinking in terms of not wanting "bad fluid" running through the new parts.

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Just now, Estremo said:

Thank you, then I guess I probably have the original. Would you just dump it as getting everything it all out and then refilling it with new coolant or also flush it completely with distilled water once before refilling it with new coolant?

 

Does it really matter if I change the water pump and thermostat before refilling? Thinking in terms of not wanting "bad fluid" running through the new parts.

 

You are only going to get about 80-85% of the old mix out by simply gravity draining it, if you want to get more out you will need to do at least one or two flushes, preferably with distilled water.  As for the new water pump and thermostat, I would just install them and then do the flushes.

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4 minutes ago, JFP in PA said:

 

You are only going to get about 80-85% of the old mix out by simply gravity draining it, if you want to get more out you will need to do at least one or two flushes, preferably with distilled water.  As for the new water pump and thermostat, I would just install them and then do the flushes.

I would prefer to install them first so that's some good news. Maybe I'm off my own topic now but what is really the advantage of replacing it all? The cooling temp is rarely an issue but of course I want to do everything I can to take care of my engine if other bad things can happen.

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2 minutes ago, Estremo said:

I would prefer to install them first so that's some good news. Maybe I'm off my own topic now but what is really the advantage of replacing it all? The cooling temp is rarely an issue but of course I want to do everything I can to take care of my engine if other bad things can happen.

 

The reason for replacing it all is that nothing is forever, particularly "lifetime" coolants.  They all break down over time, lose their additive packages and thus pH  and corrosion control.  Realistically, coolants, even so-called "lifetime" systems need to be replaced every 5-7 years, or earlier if they show signs of failing.

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22 hours ago, JFP in PA said:

 

The reason for replacing it all is that nothing is forever, particularly "lifetime" coolants.  They all break down over time, lose their additive packages and thus pH  and corrosion control.  Realistically, coolants, even so-called "lifetime" systems need to be replaced every 5-7 years, or earlier if they show signs of failing.

I'll take your advice and flush it once with distilled water. So far I have gravity drained it and think I got 14-15 litres out of it.

 

Do anyone know if it's ok to mix Porsche coolant with VW/Audi G13 coolant. People seem to use that in their Porsches so I figured I'll do that too if it's ok?

 

I already have two litres of Porsche coolant so if it's ok to mix I guess I use those to litres together with VW/Audi. And if not I will only use VW/Audi.

 

Or as a third option I buy just Porsche coolant if that's a better option. The price difference isn't that big here but my nearest Porsche dealer is really for away.

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Porsche coolant is available in 1gal container https://www.sunsetporscheparts.com/oem-parts/porsche-antifreeze-3785-l-00004330575

You will need ~3gals if you flush out all the old coolant (~6gals). I think it's best to go with Porsche and not to mix with other coolant.

 

If you want to flush out all the old coolant without removing too many hoses, I've developed a method for 996 that many have used and got great results. Perhaps you could adapt it to your Boxster.

 

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1 hour ago, Ahsai said:

Porsche coolant is available in 1gal container https://www.sunsetporscheparts.com/oem-parts/porsche-antifreeze-3785-l-00004330575

You will need ~3gals if you flush out all the old coolant (~6gals). I think it's best to go with Porsche and not to mix with other coolant.

 

If you want to flush out all the old coolant without removing too many hoses, I've developed a method for 996 that many have used and got great results. Perhaps you could adapt it to your Boxster.

 

 

I don't think they sell it in anything else but litre bottles here. 1 litre is 18 USD. Not to mention the nearest shop is 1.5 hour away. But if you really think I should go with Porsche I guess I have a drive ahead of me tomorrow...

 

Is it ~6gals in the Boxster too? I've seen some different figures and actually thought I was rather close now.

 

Your method seem very smart, I wish I had seen that before. Since I have just drained it the old fashioned way and now know how to do it and have connected all the hoses again to flush it with distilled water first thing in the morning, I think I'll stick to that plan however.

 

 

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The Boxster S takes 22 litres +/- (5.8 US gallons) to fill from empty. That's 11 litres of coolant. It's ill-advised to mix different coolants.

 

Once done and you have the engine running, don't forget to open the burp valve for bleeding air from the system ... and keep a close eye on engine temperature.

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