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Discussion Starter #1
1. My 99 DOHC Neon is due for a timing belt replacement. I am not familiar with the hydraulic tensioner. Is it recommended that I change the tensioner along with the belt and water pump? how do I compress the tensioner to install it? Also, if anyone could post a picture from a manual showing how the camshaft markings need to align that'd be awesome too

2. My speedometer is dancing around, I will check to make sure I have 12v, 5v, and a good ground at the connector. If checked the ohms on the sensor what numbers would indicate a good or bad sensor?

Thanks guys :)
 

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You probably should get a good service manual with pictures and procedures first. Don't try tackling a DOHC timing belt without guidance.
The hydraulic tensioner can be compressed in a vise and a pin used to hold the stem down until it is reinstalled and can then be released. Roll the crank 2 turns and then revisit you timing marks to be sure that they still line up. A straightedge across the cam bolt centers and a mirror can help you make sure that the marks are dead nuts on the horizontal before buttoning everything up.
The tensioner itself is probably OK, but you want to replace the rotating pulleys and water pump as the bearings get tired and you don't want a failure that could damage valves. You only want to have to do this job once.

2008-02-12_185115_dohc_neon_belt_diagram.GIF

The speed sensor may be a bad connection or a worn plastic gear. There is no real resistance test for the sensor, but if you turn it one revolution you should count 8 pulses on your DC voltmeter.
 

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Discussion Starter #3
Thanks IC, I have done a timing belt on a PT Cruiser, but that was during an engine swap when I had the donor engine out of the vehicle. I failed to mention the car has 180,000 miles on it, would the tensioner still be ok?
 

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The diagram in post #2 shows the newer-style eccentric pulley that tightens the belt as you rotate it and lock it down at the correct belt tension. Yours may still have the old-style tensioner with the pulley on the pivot arm and the hydraulic/gas spring cylinder.

http://www.factorychryslerparts.com/showAssembly.aspx?ukey_product=4436764&ukey_assembly=688397&ukey_make=1061&ukey_model=15475&ukey_driveline=6889&ukey_trimlevel=0&modelYear=0

The cylinder can usually be collapsed and reused, but I would replace the turning items that wear and ride on the belt (#15, #16, w/pump and t/belt).
 

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Discussion Starter #5
sounds good. Now back to the speedometer, I did what you should never do, and that is just throw a part at the problem. I replaced the speed sensor but my speedo will still drop to zero randomly. I did back probe the spped sensor connector and I got a good ground, a 5V reference, but on 8V on the 12V wire. This is with the connector unpluged so I believeI have an electrical gremlin that I have to track down
 

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I don't think there is 12v to the speed sensor. OR wire is 8v supply. Wt/Or is speed signal to PCM and cluster. Bk/LBu is ground. It could still be a poor connection or a worn plastic speed sensor driven gear.
In rare cases, I have found the drive gear on the differential carrier broken. Reaching down the hole with a long screwdriver, it should not be loose or turn.
 
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