w1ayne

I just had the water pump (it was getting noisy) and timing belt on my 91 LS400 (131,000 miles) changed at Lexus of Marin, CA. I am a very good mechanic but being 78 I thought I desired a break to save my back.

When I got the car back the high tension cord grommet on the LH #3 timing belt cover had not been fitted back (it is hard to get in place). Of the 4 cap screws holding this cover on the lower one was just set in it hole, not tightened. Also, the large clamp around the accordion rubber air flow pipe was loose.

Using a torque wrench, all the nuts and bolts that I could reach, which were involved in the repair, were over-tightened 64% and more, as the upper limit of the torque wrench was reached (I bought the wench just for this test, having never owned one). I have to assume that all the bolts and nuts in the repair are over-tighten. What future problems might this cause ( there appears to be none right now)? Down the line will the thin water pump case distort and the mating surfaces leak?

LScowboyLS

you really cannot tell the previous torque of a bolt by using a torque wrench, as the torque it takes to break it free is far more than it was torqued down with (straight forward physics)

while a torque wrench should ideally be used on pretty much every bolt on the car, on the vast majority of engine bolts, too much torque is mostly only a risk of shearing the bolt off, some exceptions would be: head bolts, valve covers, transmission and oil pan (where a flange sealing surface can become distorted)

water pump is a hard call, but likely will be fine if they are all over-torqued equally, as the seal is relying on a formed gasket or more likely FIPG (i.e. Permatex)

if all of those 10mm timing cover bolts are still tight, then he probably hasn't over-torqued anything, because those are very easy to break if overtorqued much at all

1sWt2GS

iTrader: (6)

my buddies have always told me that when it comes to engine bolts, it requires things to be torqued to the correct specs.

PureDrifter

iTrader: (10)

+1 on not being able to measure an already torqued bolt effectively.

timmy0tool

iTrader: (7)

agreed how can you tell 64% overtightened? that's one heck of a wrench you bought.

in all seriousness covers and the intake i can understand being overlooked (not a big deal) but then that tells me "what else did the mech overlook?" it is hard to get to the water pump bolts without removing the front covers. if it's not leaking i wouldn't worry about it. there should be a warranty on the work regardless.

denverdog

if you put the wrench on a bolt and determined what force it took to tighten it slightly more, rather than loosen it, would that give you an idea as to what it had been torqued to previously?

i'd also write the place and tell them what you found. let them say "no problem", or "we'll do it over". that way they can't say "if you'd let us know we'd have taken care of it. now our warranty is voided."

mitsuguy

iTrader: (2)

I would say somewhere around 80% of the bolts on an engine don't require a specific torque (there is a spec solely because that is what the machine that put them together was set to), and if overtorqued, so long as the fastener doesn't break, it is nothing to worry about...

denverdog is correct, to properly find out what the torque is, you would literally have to start low and go up in torque until you got the nut or bolt to move a small amount, then this amount would be 5-10% more torque than the fastener was previously torqued to...

I remove wheels all the time that require 50-100% more torque to remove than they were initially installed to... sometimes less too, its weird, and not accurate to use reverse torque to figure out what it was previously torqued to...

w1ayne

A few details. I did not break free or tighten any bolt/nut that could compromise a seal. I did remove the 10mm cap screws holding LH # 3 timing belt cover and the tightness of those are what gave me the clue of over-tightened bolts. In the testing I applied the torque wrench only clockwise.

When I am working on a car and tighten a number of bolts/nuts and think I might have missed one, I test it by applying torque but not enough to move it if, indeed, it is tight. I have been doing this for so long that I know the torque I would have used on that item and can match it. What I am saying is that I have acquired a sense of the "correct" torque for that bolt/nut in a given environment, as I assume (incorrectly) any experienced mechanic has.

The torque wrench I bought "breaks" (clicks) when the set torque is reached. By setting the torque low and increasing in value without the bolt or nut moving (which is easily felt and seen), when the highest setting of 250 in-lb is reached and it clicks, that tells you there is still more to go. This happened on the water pump nuts. The 1991 Lexus repair manual indicates 156 in-lb for those nuts. That is 64% over but it would be even higher as the torque wrench limit was reached.

My first vehicle was a WWII jeep in 1951 when I was 16. I have only ever used a mechanic in the intervening years for automatic trans repair (and the current timing belt change). My father owned a earth moving company and besides cars and trucks I worked on D8, D7, TD18 etc.

dengman

I do valve cover gaskets by feel in the ratchet and looking at the gasket

I honestly have only used torque wrenches on wheels and engine assembly. Other than that its with a wrench or ratchet by feel. I tend not to use air ratchets to tighten, I find they over tighten easily. I tend to use them to aide faster removal and assembly.

LScowboyLS

well with all of the other mistakes you have highlighted that these goobers made, working on your car, I am starting to believe that these guys are idiots and the water pump bolts may well be over-tightened

however, I do know those 10mm cam cover bolts are very easy to shear off if over-tightened, seen many rookies do this on LS400's