Need help 98 4Runner thump/knock in lower RPM range???

[91v8yota]

I bought a 98 4runner a little over a month ago from up north, 170k miles seemed like a good deal with the condition and the price. I started noticing a thumping or knocking sound. I've heard a rod knock before and it really doesn't sound like one to me nor does it sound like a valve clearance issue, this is a low pitch noise that doesn't sound metal to metal. The sound does get faster with rpm and stays consistent with the rotation of the engine, but does not change in pitch and does not get any louder as rpm increases. It does seem to get louder as the engine warms up but only slightly. The oil level is correct and the oil is clean but I am going to change it in the next few days anyway. The noise sounds like it is coming from the drivers side and somewhere in the bottom end. It doesn't really seem to be effecting anything, it runs great, good power, and there isn't even a slight miss to the engine. Just wondering if it's any kind of a common problem. I know my pickup had a knock to it but it was just normal piston slap and never really effected how it ran. Right now the noise is more annoying then anything but has not gotten worse in the past month and i drive it a minimum of 350 miles a week. I am a mechanic and have been doing it a few years, i worked of a Toyota dealer for about 3 years but never really paid any attention to the 3.4 engine in the 4runner (never saw one with an internal issue though) and worked for a Chrysler dealer for 3 years so saw a lot of their junk. Now I'm a heavy equipment/diesel mechanic so everything i work on rattles, knocks, and is completely worn out, lol. I would appreciate anyone's opinion or experience on this issue. Thank you.

[kball]

Any idea on what previous maintenance was done before you bought it? Like had the timing belt and water pump been changed? If they are the original maybe the water pump is making noise. Really though a noise like that could be coming from lots of things. I'm just guessing...

[mh808]

I have a 2002 V6 4Runner and have the same noise appear a few months ago. I have very low mileage and change oil frequently. I took it to the dealer and they "suspect" it's the water pump but not sure. They quoted me $700 to replace the water pump and $1700 to do the timing belt as well. What bothered me is that they said we can replace the water pump and timing belt and once we put it all back together, we'll see if the noise goes away. I declined for them to do the work. My 4Runner runs well except for this noise.

Appreciate if anyone can help me and 91V8yota.

Also, if anyone has good instructions on how to replace the water pump, appreciate if you can send it to me. I want to replace the water pump myself to eliminate that and the pump costs only $93 at NAPA.

[kball]

haha nice try jetwhine I still don't get why this forum protects Toyota's interests by not allowing links to the fsm.


Maybe these links will help mh808

http://www.nwtoys.com/forum/tech-art...ming-belt.html

http://www.toy4x4.net/timing_belt/index.htm

http://www.4x4wire.com/toyota/maintenance/timing_belt/

You have to remove all this stuff to get to the water pump so doing both the timing belt and the pump at the same time is the only way to go. The prices they quoted you are total BS. They are trying to bend you over! A normal price for a timing belt and water pump job is between $500-800 depending on where you go.

I haven't done it yet but I bought my kit off ebay for around $300. Had everything to do the belt and pump with all pulleys and seals and accessory belts.

Here's a link to a thread on another forum that has links to a few kits.

http://www.yotatech.com/f2/98-4rnr-l...g-belt-124993/

[dandeman]

One thing I would check right away is the harmonic damper/crank pulley.. Make sure it is tight, not rocking on the crankshaft and in good condition. When they are loose it can make a variety of sounds, some similar to a rod or bearing knock. The concern is a possible do-it-yourselfer timing belt change in the history of this engine.

Reason: When the timing belt is changed this pulley must be removed, and given its function (harmonic damper) the one bolt that locks it down securely on the crankshaft must be torqued down to 217 ft-lbs.. That's tough without the right equipment.

Engines have been severely damaged by not torquing the crank pulley/harmonic damper bolt down to the required spec.. Failure to do so will allow the pulley to rock on the key and eventually bugger up the end of the crankshaft to the point that the only practical fix is a new short block.

[jetwhine]

My idea of a forum is to help people not to hender them. Oh well "My Bad"