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308 knock at the front of the engine

Started by _The Baron_ , Aug 17 2014 09:29 PM

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#1 _The Baron_

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Posted 17 August 2014 - 09:29 PM

Got home from this morning’s run and noticed a knock/rattle sound coming from the engine at idle.

It was a deep heavy sound like that of a stuffed conrod big end bearing but it was emanating from the front of the block, too far forward for the crank/rod. It was also inconsistence with the engine timing/mechanical sequence if you know what I mean.

Whilst listening, the thermo fans kick in and the noise disappeared??? Once the fans dropped off the rattle returned and got worse when I dropped the idle a touch.

So I pulled the fan belt off and immediately the sound was gone no matter what I did with the idle. (Don’t worry I ran it only for a few seconds).

This is the second genuine GMH water pump gone to the dogs. The belt is not that tight in my opinion, just enough to stop slippage when the fans, lights and battery charge load is on. I pulled the spare new GMH pump off the shelf and opened it up and had a good look. I notice that the anti-cavitation plate was floating loose but prevented from dropping out by the impeller arrangement. However if I shook it side to side it made a sound not unlike what I was hearing?

Has anyone else got a new genuine pump and does the plate float in it too? Do I have a dud?

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#2 lx308

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Posted 17 August 2014 - 09:38 PM

I had the same type of noise years ago on a 351 in a XD. Sounded like a big end gone.

Took it to the crazy Russian mechanic, that was the only choice in Cue at the time. He had a listen, looked at me with a smile, got his can of CRC & gave the fan belt a squirt.

Wallah, noise gone.

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#3 _The Baron_

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Posted 17 August 2014 - 10:12 PM

CRC Belt grip?

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#4 rodomo

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Posted 17 August 2014 - 10:19 PM

Crank bolt tight?

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#5 _76lxJAS_

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Posted 17 August 2014 - 10:24 PM

Whilst listening, the thermo fans kick in and the noise disappeared??? Once the fans dropped off the rattle returned and got worse when I dropped the idle a touch.

are you sure it not the alternator? i wouldnt of thought the water pump would change with load?

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#6 _The Baron_

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Posted 17 August 2014 - 10:27 PM

Crank bolt tight?

I gave the pulley/balancer assembly a fair yank in a number of directions and there is zero play in it but another good point.

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#7 lx308

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Posted 17 August 2014 - 10:33 PM

CRC Belt grip?

Nope. Plain jane CRC...

I couldn't believe it!

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#8 _The Baron_

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Posted 17 August 2014 - 10:33 PM

are you sure it not the alternator? i wouldnt of thought the water pump would change with load?

Sound is definitely from the engine front, A9X alternator is down low on the driver’s side and the sound is not there although stranger things have happened.

I have wiggled the water pump pulley side to side and there is some play with a slight clunk but not as loud as when the car runs at idle.

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#9 _76lxJAS_

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Posted 17 August 2014 - 10:36 PM

do you have a gilmer belt set up?

mine is and would slip with a quick rev making a clunk noise, was hard to pinpoint where it was coming from. i first thought it was in the engine also.

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#10 _The Baron_

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Posted 17 August 2014 - 10:37 PM

Nope. Plain jane CRC...

I couldn't believe it!

OK, sounds like the belt was riding high as it fed onto the pulley and then would snap into the groove as it turned further around the back. Thereby hammering the pulley as the assemblie rotated. Hmm food for thought, worth a check before the pump change. Thanks.

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#11 _The Baron_

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Posted 17 August 2014 - 10:39 PM

do you have a gilmer belt set up?

mine is and would slip with a quick rev making a clunk noise, was hard to pinpoint where it was coming from. i first thought it was in the engine also.

Thanks for the comment, no gilmer belt (gee they sound tough) as I will be hooking up the AC later.

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#12 _76lxJAS_

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Posted 17 August 2014 - 10:43 PM

they do sound nice and look great but very impractical,

im looking to change back to v belts as the tension needed to stop it slipping isnt good for any components.

hope you find your issue mate.

Cheers

Jason

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#13 _outer control_

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Posted 18 August 2014 - 01:17 AM

Try some hair spray on the belt it may have been having a bad hair day (just a thought)

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#14 76lxhatch

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Posted 18 August 2014 - 06:31 AM

Generally by the time they get to the stage of having belt problems a new pulley is the best solution.

Baron if it has some play then sounds like maybe it is done, had a genuine one (short nose with cast impeller) die on me in a big way recently. I guess they went to the bigger bearing for a reason, could always fit one by changing the pulley and keep the original on the shelf?

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#15 _oldjohnno_

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Posted 18 August 2014 - 07:17 AM

I had the same type of noise years ago on a 351 in a XD. Sounded like a big end gone.

Took it to the crazy Russian mechanic, that was the only choice in Cue at the time. He had a listen, looked at me with a smile, got his can of CRC & gave the fan belt a squirt.

Wallah, noise gone.

Yep, saw the same thing on a red 173 many years ago. Metallic knocking noise from front of engine, sounded like alternator or maybe WP. Mechanic pulled dipstick from engine as it was running and touched it to the belt, noise disappeared instantly. So try a new belt first.

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#16 _The Baron_

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Posted 18 August 2014 - 12:12 PM

Yep, saw the same thing on a red 173 many years ago. Metallic knocking noise from front of engine, sounded like alternator or maybe WP. Mechanic pulled dipstick from engine as it was running and touched it to the belt, noise disappeared instantly. So try a new belt first.

Sound like the ticket, will do and will let you all know how it goes.

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#17 _The Baron_

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Posted 18 August 2014 - 12:15 PM

Try some hair spray on the belt it may have been having a bad hair day (just a thought)

You should know, you stared in the movie as the lead actor!

Where were you 6am Sunday morning? Going from a dairy worker to a truckie has made you soft buddy.

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#18 EunUCh

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Posted 18 August 2014 - 03:56 PM

Bit of dipstick oil on the belt is the best way to fix rattly/knocking cruisers as well,soluble oil in a trigger pack works ok as well,mite save a dipstick

if it gets in the wrong place.

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#19 _outer control_

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Posted 19 August 2014 - 05:30 AM

You should know, you stared in the movie as the lead actor!

Where were you 6am Sunday morning? Going from a dairy worker to a truckie has made you soft buddy.

When the auto is sorted i will join you i will be able to enjoy my ice cream and ice coffee while i drive

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#20 TerrA LX

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Posted 19 August 2014 - 01:18 PM

I have wiggled the water pump pulley side to side and there is some play with a slight clunk but not as loud as when the car runs at idle.

LOL, a slight clunk when wiggled by hand, imagine how it feels at 6000rpm...

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#21 _The Baron_

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Posted 21 August 2014 - 06:10 PM

LOL, a slight clunk when wiggled by hand, imagine how it feels at 6000rpm...

With a 2.6 diff I never reach 6000rpm. I would exceed the highway limit at those revs in first gear!

When "clunked" by hand it takes some effort and a special technique. Can't here the problem at 6000rpm either, only at idle.

Still yet to get the new fan belt.

With a 2.6 diff I never reach 6000rpm. I would exceed the highway limit at those revs in first gear!

When "clunked" by hand it takes some effort and a special technique. Can't hear the problem at 6000rpm either, only at idle.

Still yet to get the new fan belt.

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#22 _The Baron_

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Posted 23 August 2014 - 08:22 PM

Update.

I have replaced the fan belt but the sound is still there, same as before. Bugger.

Next task it to double check the balance bolt is tight. This might sound like an easy task but I have the Wombat plough which makes it impossible to get access from below. The Wombat Plough is a front spoiler with a pan that runs back to the x member which is a night mare to remove. So I must go through the top however I have a large radiator with a set of fans which gives me about 2" of access into the double pulley arrangement to get to the bolt.

Does anyone know what size socket I will need?

Is this bolt left or right hand thread?