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Whistle under the hood

7076 Views 29 Replies 12 Participants Last post by  eekthekat
It is a little bit colder these days in montreal...
This morning I started the 1998 Rodeo (3.2/ Automatic/ 50K miles) and between 1900 and 3000 Rpm I hear a whistle comming from the engine. It cleared away as the engine warmed up. I did not push it at all so I can't tell if there is a power loss or not. First day it does that.

Is that the first sign of a leaking intake gasket?
Could it be a stupid idller that starts to rock not roll?
Anybody has ever seen this before?
Should I simply raise the volume on the radio or leave the truck in the driveway for a week to punish it?

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On my car it was the beginning of an intake manifold gasket leak. The performance issues took a little more time to manifest.
How much to get that Holly seal replace.
Is like 50$ or more like 1000$
Is that a week-end mechanic kind of job or more like an open heart surgery?
I just use that new link at the bottom of the main page that brings you to speedy car parts. I can find the price for it but no drawing.
Does anyone know where i could find an exploded view of my engine (to see witch part I need)
One on either side of the intake manifold where it sits on top of the engine.

I didn't do this job myself so I honestly can't say what needs to be shuffled around in order to get it out and then put it back.

I've done intake manifolds before and I wouldn't say it's a terribly difficult task. You just need to work carefully and ensure that NOTHING gets into the heads.

IIRC, the parts are cheap and probably ~$70-90 at the dealer. The labor is where they'll get you. I would EASILY expect to pay $300-400 in labor for this @ my local dealer's rate of $75/hr.
Howdy. If you suspect a pulley going out, try using a mechanics stethoscope to find the problem. Or take off your belts and turn the pulleys by hand. The should be smooth and not shake at all from side to side.

If you suspect an intake manifold leak, the easiest way to find this is on the smoke machine. If you don't have one or access to one, try using some water in a spray bottle. Raise your RPMs to where you have the problem and then spray some water along the intake manifold gasket. If the water temporarally "solves" the problem, it is probably the intake manifold gasket. Just be very careful where you spray the water.

This job is not too hard, but it does depend on your comfort level. If you keep track of all the stuff you take off (label and/or take pictures), it shouldn't be a problem. Make sure to check the mating surface of the intake to make sure it is not warped. I would also recommend the use of a sealant when installing the new one. I like to use the red spray that permatex puts out. Also, don't forget to torque the intake to the proper ft/lbs (or in Canada the proper newton/meters!). Good luck.

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Thaks for the answer, I will keep watching it for the next days and I will probably try to do it myself at christmas time.
The only thing I don't understand is the newton meter thing, It sounds like a cookies brand name. :lol:

Thank you again
Isn't everything in Canada measured in the metric system?
officially yes but some units are too weird, we just kept using the good old english system.

I got 93 000 km on my truck
but there is 28 psi in my tires.
V2 said:
officially yes but some units are too weird, we just kept using the good old english system.

I got 93 000 km on my truck
but there is 28 psi in my tires.
thats priceles :lol: :lol:
the intake gasket is the most likely source of your noise it is not a major job you should be able to it at home on youor own in about two hours maybe even less than that I can get it done in about 40 minutes but I do this on a regullar basis what I do to determine if it is a leak at the intake gasket is while engine is running spray some carb cleaner at the base of the intake manifold good luck
I know brake cleaner is pretty rough for some materials. I know it can melt some rubber compounds. Is it going to eat my seal?

I openend the hood this morning and gave it some gas,
Dam its noisy, I am surprise a stupid air leak could be so loud.
Could a bad iddler make noise when cold only?
He didn't say to use brake cleaner; He said carb cleaner.

Good thing you thought about it before doing it. :)

Brake cleaner would eat up lots of other stuff on your engine that you wouldn't want to eat up. :)
I sprayed some carb cleaner at the base of those aluminium vertical manifolds, no RPM change,
I tryed to move all pulleys, idller wheels... where the belt travels and I found that the water pump pulley can move a little bit in and out. Not very much, but it is not as stable as the other one. Is that normal !!! it is not moving very much...

Tomorow, I will try to spray some WD40 on it to see if I get a new tone...
Howdy. V2, don't use the WD40, this will only cause a bunch of smoke to bellow from under the hood. If carb cleaner didn't do the trick, then your intake manifold might not be to blame for your "whistle". The problem is here at the board, it's difficult to determine what kind of "whistle" you are describing. What you might call a whistle, I might call a howl.

If your water pump is loose, it may be starting to go. If the bearings are starting to seize, your belt could be starting to slip and hence causing a "whistle" noise. What kind of mileage do you have on the engine? Does it feel nice and smooth when you turn the water pump pulley? Is there any signs of glazing or slipping of the belt on that pulley? Are your top and bottom radiator hoses the same temp when the engine is at full temperature? Are you overheating at all?

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Temperture is fine (always in the first half)
The noise only last for 3 minutes. Hapens once a day when cold and slowly goes away. I can park it for the entire day and it does not do it when I leave the office at night.
I was in a trafic jam last friday, temperture was fine.
Tomorow morning I will spray some WD40 on the pump itself. Probably between the center bolt and the rubber seal that turns with that small wheel.

It is loud (probably arround 70db).
I will also try to cover the pump with a piece of cardboard to try to isolate the source.

How do you spray the carb cleaner on the inside of the manifold?
It's easy to do on the outside but the inside...
Does the failure always happen on the outside of it?

My guess is that the bearing or the blades inside the water pump are rubbing against something but as temperture goes up, metal expand and everything is fine again. Thats until the temperture goes bellow like 35 F and the cycle restart making me go crazy.
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V2- you want to spray the carb cleaner around each intake runner, where they mate up to the cylinder head(s). Basically you are spraying around and under the main intake chamber & listening for a change in idle. I wouldn't spray WD40 anywhere around a belt driven accessory. You'll wind-up slipping & destroying your serpentine belt. You cannot get at the water pump unless you pull all the front accessories off the engine & pull the timing belt covers. The water pump is burried in there & is driven by the timing belt. That pulley up top near where the radiator hoses go into the block is not the water pump (I thought the same thing at first :oops: ). That's just an idler pulley. G/luck
Howdy. Hey guys. V2, sorry, I misunderstood your post on the WD40. But still, Joel is right. Don't use this on your pulley, it's a bad idea.

Joel you are obviously more familiar with the lay-out on these motors. :) On the idler pulley, just in case you did not know, most of these have a bearing in the back which you can remove. Take it off the vehicle and see if there is a clip holding in a bearing. If so, you are in luck. So, don't go out and buy a whole new pulley assembly unless it's damaged in some way. There may be some interchangeability here also if you can find one in a junk yard, but for the cost, I'd personally go for a new bearing. Good luck.

This morning I removed the belt and ran the engine for 20 seconds, No noise. Put the belt back... noise
Sprayed a little bit of WD40 on the beaaring: change of tone. I did not put too many, it goes every where. So if there is a long term side effect to the WD 40 on the belt I will let you know shortly :oops:

Just an iddler: That makes sense I could not figure out why the bolt was not turning with the pulley. That a good news, it mean I will be able to fix my problem for just a few dollars.

So thats a good truck it always gives a warning when something is broken and you can fix it with your pocket change. ( I am not waiting for your comments on this one, just let me dream) :wink:

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