Tapping felt through thermostat cover

twflyer · 04-21-2009, 12:56 AM

This is a great, informative website you guys have. I'm glad I found you.
I've searched for similar threads to my "problem" with no exact match found. There's plenty written on ticking, tapping, clicking and knocking, but none of the threads that I've read mentioned the description of a VERY noticeable tapping felt registering through the thermostat housing, as in my truck. I have a 1990 extra cab, manual, w/3vze - 190,000.

It starts easy, runs great, just passed smog. It just has this light/moderate, ticking/tapping/knocking/diesel-sounding noise coming from the front of the engine. The noise can either be noticeable or not - usually is. It goes away (drowned out by engine roar I presume) at higher rpms. It almost sounds like something tapping against a shroud most of the time, therefore not a real "hard" tap. Although it does follow the rpms up and down with a rather sharp ticking. It's not really noticeable from the cab unless it's quiet out and at idle.

Again, the one difference in everything that I've read is that putting my finger on the Thermostat housing there is a steady beat to the tapping noise. I can also feel it, although less so, on the water hoses leading from the thermostat. I can barely feel it on the timing belt cover. There is no other place on the engine that I feel it, even immediately adjacent to those spots mentioned above. Everywhere else is smooth.

Not being much of an auto mechanic, I thought it might be a water pump sort of thing. I dropped the belts from the alternator and steering pump, thinking I could isolate the water pump, and started the truck for a couple seconds. The noise was still there and still registering through the same places.

Any thoughts?
Thanks.

This ad is not displayed to registered members.
Register your free account today and become a member on Yotatech!

vital22re · 04-21-2009, 01:46 AM

well water pump is drivin by the timing belt on that moter. When was the last time the timing belt was changed? It could be from the idler pulleys or tensioner pulley on the timing belt.

twflyer · 04-21-2009, 10:41 AM

Ahh, so I didn't isolate anything with dropping the drive belts. I kinda thought that. Also I just discovered that I was wrong about the thermostat housing. The tapping noise is coming through the water outlet (top of the motor).

Timing belt, idlers, water pump, etc all appear to have been replaced about 60k ago.

04-21-2009, 01:46 AM	#2 (permalink)
vital22re Registered User Join Date: Feb 2006 Location: kirkland washington Posts: 679	well water pump is drivin by the timing belt on that moter. When was the last time the timing belt was changed? It could be from the idler pulleys or tensioner pulley on the timing belt. __________________ 92 toyota truck 3.4 5spd 4.56 gears magna flow cat and muffler2 1/4 piping isr mod to intake 1.5 bjsfront add a leafs and 2inch lift shackles rear rancho shocks all around sitting on 265/75/r16 nitto terra grapplers

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Running Cold. Thermostat open? OEM thermostat replacement?	Harold Of The Rocks	86-95 Trucks & 4Runners	17	01-28-2009 08:11 PM
Just felt an earthquake....	Tacoclimber	Off Topic Talk	4	12-06-2008 09:47 AM
No wonder My clutch felt so bad	nmtoy	86-95 Trucks & 4Runners	18	04-13-2008 07:55 PM
Felt left out not having a winch so...	White83	Offroad Tech	5	01-22-2007 03:03 PM
Thermostat Cover Sensor	drewberglund	95.5-2004 Tacomas & 96-2002 4Runners	5	01-10-2005 09:40 AM

04-21-2009, 10:41 AM	#3 (permalink)
twflyer Registered User Join Date: Apr 2009 Posts: 0	Ahh, so I didn't isolate anything with dropping the drive belts. I kinda thought that. Also I just discovered that I was wrong about the thermostat housing. The tapping noise is coming through the water outlet (top of the motor). Timing belt, idlers, water pump, etc all appear to have been replaced about 60k ago.