1999 Chevy Suburban Leak Questions


#1

We replaced the intake manifold gasket on our 1999 Chevy Suburban 1500, 2-Wheel Drive with a 350 vortec engine. We fear that when we tightened the bolts down to torque specs but did not account for the lack of torque with an extension. After calculating this, it seems that we only had 7.83 ft-lbs when we needed 11 ft-lbs. Could this be the cause of a leak that didn’t make itself apparent until about a week and a half after the repair?


#2

As long as the axis to the fastener from the torque wrench is a strait line, the torque reading won’t be skewed.

It’s when you use an extension along with a U-joint/swivel socket and a torque wrench where things can get messed up.

Tester


#3

If you did indeed torque to 11 in-lb, then there is your problem. Torque specs for intake bolts are 11 ft-lbs. Not in-lbs.


#4

@“pete peters” thank you but I must have made a typo, it is 11 ft-lbs.


#5

@Tester Yeah, we used an equation to calculate a loss of torque when using a straight line extension like we did, is that just garbage then? Not true?


#6

It doesn’t matter if you use a regular socket, a deep well socket, along with an extension, as long as it’s a straight line from the torque wrench to the fastener there is no torque correction factor required. The torque is being applied on a straight axis.

It’s when you approach the fastener at an angle with either a U-joint or a swivel socket is where the torque reading can be skewed.

Tool manufacturers recommend avoiding using such U-joints or swivel sockets when using a torque wrench because it’s not known at what angle the fastener is being approached. So it’s impossible to establish a torque correction factor.

Instead they recommend that a crows foot wrench be used to access the fastener. Because if you know the length of the crows foot wrench from the axis of the torque wrench to the center of the fastener, you can establish a torque correction factor.

Tester


#7

There’s another problem with using U-joints with torque wrenches; U-joints do not transmit torque in a linear fashion. A constant torque in results in a sinusoid shaped wave out. The peak gets higher than the indicated torque. The greater the articulation of the joint, the more inaccurate the torque wrench reading, and it’s impossible to know how much torque the nut/bolt is being tightened to.

Re: the crow’s foot; as long as you can keep the crow’s foot in line with the torque wrench you can measure the length from the nut/bolt axis to the torque wrench axis and use the percentage of the length it adds as a multiplier for the indicated torque reading, but as soon as the torque wrench ratchet gets out of alignment with the crow’s foot the force is being applied on a vector and calculating that gets complicated. To illustrate, if the crow’s foot were to get turned around 180 degrees from the line of the torque wrench, you’d have to use the reciprocal of the percentage you factored in to start… the distance from the hand-end of the torque wrench to the turning axis of the bolt/nut would be 1" shorter rather than 1" longer (if the crows foot adjustment were based on a 1" measurement).

Bottom line; I don’t recommend using any attachments with a torque wrench that allow the applied axis to vary from the axis of the hardware being torqued.


#8

Here’s how to correct the torque reading when using a crows foot wrench along with a torque wrench.

http://www.engineersedge.com/manufacturing_spec/torque_wrench_1.htm

Tester


#9

@RaiderNationNews

I believe you opened a new thread, instead of continuing your previous thread . . .

Why?

And you still haven’t answered my earlier questions . . .

I believe on this engine, you have to make your own end gaskets, using rtv. Did you lay a nice solid bead

Any chance the rtv sealing bead got disturbed too much when you dropped the intake back into place. If you had to move the intake to line up the the holes once it was down, you may have created a path for coolant and oil to leak out.

Were the sealing surfaces extremely pitted?

How did you prep the sealing surfaces on the heads and the intake?

Exactly what tools did you use?

No offense, but there are many guys who go WAY overboard in trying to get that sealing surface looking all shiny and glossy. They use extremely aggressive methods to achieve this. And when all is said and done, too much material has been removed, the surface is shiny, but not straight and correct anymore, and it won’t seal properly.

Does this sound familiar?

I apologize if this sounds offensive, but many guys are guilty of this mistake in prepping sealing surfaces for a new gasket


#10

OP, did you use a torque wrench to do this, or just a regular wrench and some arithmetic? The reason I ask, I sometimes have used a regular wrench when the torque wrench won’t work. For example when tightening axel nuts, those have to be really tight, and my torque wrench won’t read that high. So I use my own weight, and stand on the breaker bar at the corresponding distance from the bolt to get the proper torque. You didn’t do something like that, right?