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ISB Noise From the Heater Box Area
From Vol 27 of the Star Center News
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 1998-99 24 Valve Diesel Trucks Whistling or Moaning From Heater Core/Heater Box Area

There have been some reports of a whistling or moaning from the heater core/box area at approximately 1500 RPM in the 98-99 Dodge 24 valve diesel truck, check the following:

Check the heater core restriction fitting located in the top of the cylinder head. It should have a tapered rubber insert that is shaped like a funnel.

If the hole is straight through, replace the fitting with fitting PN 05011901AA.

If the noise is still there after installing the correct fitting, move the fitting forward two ports and add about seven inches of heater hose.

We have had several reports from techs who are using a Jeep heater hose PN 55036145. This hose has a 90 degree elbow at one end and is long enough to replace the old hose with one piece which gives the factory original look.

Additional Comments From the Mail Lists
> I have a strange whine coming from the intake area on my 98 ISB.
> It doesn't sound like the turbocharger, and it is most pronounced at
> about 1500 rpm. Any ideas?

Subject:   Re: Strange Whine
Date:       Thu, 25 Mar 1999 08:27:30 -0800
From:      Dave Crego <>
To:          Turbo Diesel List
Sounds like you have the old engine howl problem.  It's caused by the heater core restrictor located in the nipple at the engine block.  It's located inside the nipple at the block for the  heater hose on the farthest passenger side of the two tubes, that comes off the engine and into the firewall.  On the 24v it's the nipple at the rear of the engine. Remove the nipple and pull out the plastic restrictor (look close as I hear it may be hard to see the plastic restrictor as it may look like part of the nipple), on the 24v it's a rubber washer, and reinstall the nipple.  Very little coolant loss when doing this.  I had heard about this and thought "no way".  Other attempts to find the noise failed.  So I tried this fix and it solved the problem.

Try it you'll like it.

Subject:  WHINE
Date:      Thu, 25 Mar 1999 09:57:36 -0800
From:      scott <>
To:          turbodiesel

I had the whine in my 24V... we fixed it by removing the inside sleeve of the heater hose hook up at the back of the engine where the hose goes to the cab.  We removed the hose from the engine and inside the fitting is a 'sleeve' which can be removed with needle nose pliers.  Once that restrictor type sleeve was removed...presto no more are describing this dealer replaced my heater core thinking that was the problem...he was not far off...use a stethoscope on that hose up to the fire wall at 1800 rpm and you'll hear it loud and clear.  I was concerned with the restrictor piece being removed that it would cause poorer heating in the winter...made it better!  I have not had that whine since the day we pulled out that restrictor on the fitting.


Subject:   Re: WHINE
Date:       Fri, 26 Mar 1999 00:40:34 -0800 (PST)
From:      Hal Hildebrand <>
To:          turbodiesel

It turns out that there is/was a little restrictor in the heater supply fitting on top of the head. I removed the fitting and pried out the restrictor and re-installed the fitting in the top of the head, then went for a test-drive. NO MORE WHINE or MOANING !!!!! hurrah!! That noise was driving me crazy. Thanks to everyone that had the fix for this crazy noise. BTW the "restrictor" or orifice looks kinda like a small garden hose washer.

Douglas Hildebrand (AKA Big Kahuna).



Thanks to Bob Bergevin for providing the Star Center information
Also thanks to Terry <> who updated the part number

Last Update: August 23, 2001