Possible to Overtighten Subframe bolts?

7993 Views 25 Replies 7 Participants Last post by Dead Centre, May 31, 2005

FlyPenFly

Discussion Starter · May 27, 2005

I am experiencing a CLUNK over speed bumps unless I take them extra extra slow so I figure I might as well try this free exercise of retightening my subframe bolts.

I don't have a torque wrench and don't really plan on getting one. Is it possible to over tighten the subframe bolts? I was going to just handtighten them.

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Slaab4life

· #2 · May 27, 2005

FlyPenFly said:
I don't have a torque wrench and don't really plan on getting one. Is it possible to over tighten the subframe bolts? I was going to just handtighten them.

I hope you have a big wrench. Even with my 2 ft torque wrench I was unable to turn the subframe bolts (in fact I snapped the 3/8" socket connection) trying to loosen them. You may get lucky and find a loose one and know where to start, but I don't know how tight you'll be able to get it unless you have a 3, 4 or 5 ft breaker bar.

Sure its not a strut mount or something?

Dead Centre

· #3 · May 27, 2005 (Edited)

FlyPenFly said:
I was going to just handtighten them.

Err No...

That won't do at all. You need to take them to full torque for the subframe to do it job. Its job is integral to chasis squreness and rigidity.

The torque settings and order of tightness are very important.

Settings here.

Torque Settings Sub Frame Front bolts (x2) 85lbft or 115Nm

Sub Frame Centre bolts (x2) 140lbft or 190Nm

Sub Frame Rear bolts (x2) - Done in two stages Stage 1 81lbft or 110 Nm

Stage 2 Tighten through a further 75 degrees

Taken from my writeup here

Dead

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earthworm

· #4 · May 27, 2005

One of many reasons why cars are expensive to maintain. A man can easily spend over $200 for the necessary tools just to tighten these screws alone...But my 1/2" tools should be able to handle everything..

Each screw must be removed and examined (rust), then repaired as necessary..
The primary reason for torquing a screw is to prevent over tightening and resultant damage.....

earthworm

· #5 · May 27, 2005 (Edited)

Dead Centre said:
Err No...

That won't do at all. You need to take them to full torque for the subframe to do it job. Its job is integral to chassis squareness and rigidity.

The torque settings and order of tightness are very important.

Settings here.

Torque Settings Sub Frame Front bolts (x2) 85lbft or 115Nm

Sub Frame Centre bolts (x2) 140lbft or 190Nm

Sub Frame Rear bolts (x2) - Done in two stages Stage 1 81lbft or 110 Nm

Stage 2 Tighten through a further 75 degrees

Taken from my writeup here

Dead

Corrections noted..

Slaab4life

· #6 · May 27, 2005

140 ft-lb (190 N-m)

Dead Centre

· #7 · May 27, 2005

Sorry.....;oops:

That keeps happening its an error from the original writeup - upload on munkis site...

Dead

FlyPenFly

Discussion Starter · #8 · May 27, 2005

Okay sounds like I need to bring it into a specialist or dealership to get it done... any idea on fair price?

philosophicaldreamer

· #9 · May 27, 2005

FlyPenFly said:
Okay sounds like I need to bring it into a specialist or dealership to get it done... any idea on fair price?

I had it done for me for free by my mechanic, but he has told me that they charge about $50 to do this.

Ta-ta, janusz

earthworm

· #10 · May 27, 2005

The re torquing of the subframe bolts is or should be a part of a properly performed service/inspection , I'd think this should take about 20 minutes.. Sometimes the mechanic will run into rounded bolts, rust, seized screws and broken welds ....

But , it usually takes about 20 minutes to bring in the car, do road tests and paperwork, and not even turn a wrench; so yes, $50 is reasonable..
But why not have the full service done all at once - yes, I know this is costly....

FlyPenFly

Discussion Starter · #11 · May 27, 2005 (Edited)

Well I've done a lot of the service myself but this seems a bit specialized... so far after owning the car for a little less than a year...

a few fully synth oil changes (mobil1 15w50, i drive in florida, oem saab filters)

new spark plugs (ngk)

new pirelli pzero nero M+s tires (went slightly higher profile with 55)

radiator flush

short belt mod (upper idler pully replaced)

heat insulation/foil around pipe

air filter changes

auto transmission flush and fill

two alignments

cabin filter replaced

power steering basted and fill twice

techron cleaner twice

Fuel pump replaced by dealership ($600)

I am planning to get the rear anti sway bar, replace the DIC since I have no idea how many miles are on it (I'm at 97.3k), and change out brake pads and flush. Also there's a slight problem with my Touneau cover which I'd like to get fixed with the brace kit....

When I got the car I almost immediately developed a problem with one of the rod bearings which the dealership fix and replaced. They also supposedly retorqued the subframe about a year ago from today too. But i've put on a lot of miles on it since I got it which included driving cross country.

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Dead Centre

· #12 · May 27, 2005

If you have done all that get of yer horse and buy a torque wrench.

You will always use it again.
Why pay someone to do this!! You don't even have to jack the car up..
although its a little easier if you do.

Dead

FlyPenFly

Discussion Starter · #13 · May 30, 2005

Okay I think I will, which of these would be recommended, or should I get something else entirely

http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00944690000

http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00944642000

http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00944978000

Also, can I use these to retighten the head bolts?

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Dead Centre

· #14 · May 30, 2005

Hi Fly...

To be honest none of em. Beam torque wrenches are ok but really they have had their day.

This is the sought you really want. Known as a micro torque wrench.

I know its a little more expensive but its a better bit of kit.

You could probably find one of these used on Ebay USA.

You will need a scale that goes upto 150 ftlbs. Also a 1/2" drive is preferable. WHY? Well you are taking bolts and nuts up real tight you need a big socket lug to take the styrain as you tighten. I have sheared 3/8 fittings and also split 3/8 drive sockets.

If ya need any help understanding what to do get in touch happy to help.

Dead

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FlyPenFly

Discussion Starter · #15 · May 30, 2005

Darn these links on Sears seem to die out on time, probably session based.

Can you give me the part or item number?

JMarkert

· #16 · May 30, 2005

More SC weirdness. It works for me. Here it is, just in case Mr Centre has gone to sleep.

Sears item #00944595000 Mfr. model #44595

PMI

· #17 · May 30, 2005

FlyPenFly said:
I don't have a torque wrench and don't really plan on getting one. Is it possible to over tighten the subframe bolts? I was going to just handtighten them.

FYI, Autozone has a very liberal tool lending program. Basically you pay for the tool, and they refund your money when you bring it back.

Having said that, I recently inspected my subframe in anticipation of dropping the oil pan, and I do not see these bolts just getting loose on their own, unless someone did not torque them correctly.

Btw, I was warned against messing with the bolts w/o supporting the engine, first from the bottom with a hydraulic jack, then from the top with a beam.

The reason given was that when the engine is resting on the subframe, it deforms it slightly and puts strain on the bolts. This makes it difficult to loosen them, and impossible to retighten them to the correct torque. So you could loosen and tighten the bolts to what you think is right, even one at a time, and still end up with something worse than before.

In other words you only get the specified torque if you are tightening the bolts w/o the weight of the engine on the subframe.

I read all the time how people just "loosen" them to replace engine mounts or the oil pan, so I would welcome someone telling me I can do it without the extra equipment myself... <hint>

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Dead Centre

· #18 · May 30, 2005 (Edited)

JMarkert said:
More SC weirdness. It works for me. Here it is, just in case Mr Centre has gone to sleep.

Sears item #00944595000 Mfr. model #44595

Hi J..

Mr Centre is wide awake infact its early evening here on a glorious English summer day.

i am always awake if SC has an interesting topic to discuss, not much of that of late..:roll:

So for Mr Flys interest here is a listing from EBAY USA, Search term Torque wrench... LIST

Many good candidates and cheaper to.

Dead

As an edit...

PMI said...

In other words you only get the specified torque if you are tightening the bolts w/o the weight of the engine on the subframe.

Correct. So you should always really use a engine support beam. Mind you if you are removing the sub frame you really don't want to try and support the engine with your arm.

:lol:

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earthworm

· #19 · May 30, 2005

But, did the dealer do it correctly ?

I'll bet the mechanic simply placed the wrench on the head and tried to "tighten".
I know better,
Every five years or so a man should do this task as described below.

Support the engine and transmission (PMI is on the stick,again)
Remove one bolt at a time, clean, examine, check for rust and cracks - the subframe should be clean.
Reinstall and torque to the correct figure with a wrench that has been calibrated.
A torque wrench from Autozone that has been used by every cowboy in Dodge City ??
Our torque wrenches had to be re-calibrated every 6 months (I think)..

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FlyPenFly

Discussion Starter · #20 · May 30, 2005

The place that did it was a Saab/Volvo specialist center/dealership. They did the rod bearing replacement so I want to say they did but the CLUNK over speedbumps is weird especially because my suspension seems fine and it only with the front not the rear.

Okay so the engine needs to be supported (no tools for that), hmmm... now I'm conflicted again and sounds like a dealership job... argh!

Maybe I'll ask them to check the head bolts too.

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