Broken Timing Belt - Hyundai Forums : Hyundai Forum
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post #1 of 6 (permalink) Old 06-07-2009, 07:07 PM Thread Starter
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Hi All,

Timing belt has broken on our 2004 Sonata (2.4 4cyl. DOHC) In the process of changing it now and working on that darn crankshaft bolt. Anyway, I did some research and have not been able to come up with a definitive answer to the following question:

Is this an interference or non-interference motor (do valves strike the pistons when the timing belt breaks?). Obviously I will be a happy guy if this is non-interference and I still intend to do a compression test prior to pulling the cylinder head, but I thought this might be a good place to get a definitive answer. Otherwise this might be a might bigger job that intended.

Thanks in advance!
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post #2 of 6 (permalink) Old 06-08-2009, 12:54 PM
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you will likely not want to read this but it is an intererence engine and damage to the valves is very likely



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post #3 of 6 (permalink) Old 06-08-2009, 10:59 PM Thread Starter
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QUOTE (montego @ Jun 8 2009, 11:54 AM)
you will likely not want to read this but it is an intererence engine and damage to the valves is very likely
Ordered some of the parts today and the guy at the autoparts store informed me of my misfortune. I plan to put on the new belts and then do a compression test to check everything out before pulling the head. Is there anyone out there with a visible diagram of where the timing marks should be on the 2.4 dohc. I tried hma service, but it looks like their pen was out of ink when they drew those drawings. From what I could make out it appears the dowels on the cams should be pointed straight up and with #1 at tdc, but I can not tell for sure with the drawings.
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post #4 of 6 (permalink) Old 06-09-2009, 04:30 PM
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Dear bit,

Welcome to the wonder of interference engines. You are correct that the drawings are not very good.

1. The two camshaft sprocket marks (mine are blue) point straight up to the two 'arrow' marks on the valve cover.
2. The crankshaft 'V' slot on the inner plate points to the tip (at about 10 o'clock position) of the mount for the tensioner pulley. I know it does not really look like the hma drawing. I had to buy the Haynes manual to be sure myself.
3. The rear balance shaft sprocket (mine had a white paint dimple) matches the arrow (mine was painted white) on the engine block on the left at the 9 o'clock position.
4. The front balance shaft has a good drawing so use that one.

I did like you and gambled that I had not bent any valves. Do install your balance shaft belt, and timing belt. To get all the timing marks aligned, you likely will have to move the crankshaft. If you need to move the crankshaft more than 5 degree left or right ( no more than 5/16"), you can do this without harm. BUT that is highly unlikely. So make sure you remove all of the camshaft journals off of the two camshafts before you rotate the crankshaft more than 5/16". This will prevent the camshafts from opening the valves, so you can 'freewheel' the engine. Once you have the timing marks lined up, you can reinstall the camshaft journals and torque to spec.

After you get your inner balance shaft belt and timing belt installed, do not install the outer covers and belts yet. Static time the engine by turning clockwise 3 times with a 22mm wrench on the crankshaft. Use a helper friend up top to listen and observe the movement of the valve train for any sticking or binding noises. If your engine was like mine, you will hear 'plink' and the two bent valves will break at the bend line and drop into the cylinder. You will definitely feel if the valves are bent, as they will bind during the revolution of the engine. If the two valve heads break off, they will literally not let you turn the engine over so don't force it.

Since I had the head off, I could tell from the clearances that it is almost impossible not to have bent valves if you broke a timing belt. Sorry. I can give you a source for a cheap, fast, professional cylinder head if needed.


Where's my bailout?
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post #5 of 6 (permalink) Old 06-10-2009, 05:21 PM Thread Starter
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Cylinder compression tests revealed that #4 had abolutely no compression, so I am pulling the cylinder head yet.
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post #6 of 6 (permalink) Old 06-16-2009, 05:26 PM Thread Starter
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Head bolt torque

So anyway we are back with a repaired cylinder head (2 bent valves on #4) and a new head gasket kit. I am stuck with a question after reviewing the torque specs on hmaservice: That is I am using the old head bolts with a new gasket kit, do I use the torque specs for new parts or the torque specs without new parts?

The spec seems to read for new parts:
48 ft pounds - then release the torque - torque to 14 ft pounds + 90 deg + 90 deg

Used parts
14 ft pounds - then 90deg + 90 deg

The drawing seems to indicate the head bolts being the new or used parts, but I am looking for some confirmation from you folks.
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