Crankshaft bearing bolts: Measuring tightening torque

Hello forum,

"At my AXG TDI 111kW engine in a VW T4 manufactured in 2002, the workshop checked the torque settings of the connecting rod bearing bolts and the crankshaft bearing bolts. Specifically, the latter are known to sometimes loosen on this engine type, which can potentially cause major damage."

The connecting rods were tightened to 60 Nm each (measurements for rods 1, 3, 4, and 5), while the second connecting rod was tightened to 52 Nm initially, but then adjusted to 60 Nm. All crankshaft bearing bolts were at the specified torque of 65 Nm.

Since measuring the torque essentially only works with a slight further tightening, was the workshop's procedure permissible, or do all the screws now need to be replaced?

I mean, for the following two reasons, the screws do not need to be replaced:
- These are not stretch bolts, and the procedure described above would be dangerous in that case. The measured torque values almost exactly match the specified torque values, making it unlikely that the bolts will be overloaded.

Will I get approval from the forum for this procedure (i.e., putting the oil pan back on without replacing the crankshaft and connecting rod bearing screws)?

Thank you and best regards.
Kurt.

The connecting rod bolts should be tightened to 30 Nm plus 90 degrees, and the main bearing bolts to 65 Nm. That is correct.

Die Pleuelschrauben sind auf jeden Fall zu erneuern! Woher willst du wissen, wo du vom Anzug her jetzt stehst?!

Unfortunately, you can't easily replace all the screws for the main bearings. For the two on the last bearing bracket, flywheel side, you would have to remove the oil pan, which means removing the transmission and clutch/dual-mass flywheel.

Okay, thank you.

So, the connecting rod bolts are stretch bolts, and that's why they need to be replaced now because you shouldn't tighten them any further.

But regarding the crankshaft bolts, is it okay to leave them as they are?

TDI-GTI-4-Motion wrote:

The connecting rod bolts are tightened to 30 Nm plus 90 degrees, and the main bearing screws are tightened to 65 Nm, which is correct. Die Pleuelschrauben sind auf jeden Fall zu erneuern! Woher willst du wissen, wo du vom Anzug her jetzt stehst?! Die Schrauben für die Hauptlager kannst leider eh nicht alle ohne weiteres wechseln. Für die beiden am letzten Lagerbock schwungradseitig, müsste der Dichtflasch runter, sprich Getriebe und Kupplung/ZMS runter. {}

That's correct. When the connecting rod bolts are rotated by 90 degrees, they stretch (deform, elongate), and the torque reaches an unknown limit.
A stripped screw that has been re-tapped is longer than a new one.

The 60 Nm torque reading determined by the workshop is likely below the yield strength, because if it were above that limit, one could have continued tightening until the screws came loose.
The foolproof and guaranteed solution would have been to replace the connecting rod bolts and tighten them according to specifications.
However, I lack the experience with this motor to know whether checking a torque value just below the specified limit (i.e., continuing to turn after measuring the torque at 90 degrees) might be sufficient.

Best regards, Rainer.

Kurt.M wrote:

So, the connecting rod bolts are stretch bolts, and that's why they need to be replaced now, because you shouldn't tighten them any further?

That's correct; you don't know if they are already overstretched, but it's likely.}

"For the E36 (BMW), the 10.9 grade screws should already be standard equipment. Have you checked? If, for some reason, they are still 8.8 grade, then replacing them would definitely be recommended."

TDI-GTI-4-Motion wrote:

Die Schrauben für die Hauptlager kannst leider eh nicht alle ohne weiteres wechseln. Für die beiden am letzten Lagerbock schwungradseitig, müsste der Dichtflasch runter, sprich Getriebe und Kupplung/ZMS runter. {}

"ARP offers a stud kit, and the product description states:"

ARP wrote:

The ARP head bolts can be replaced while the engine is still installed. Lediglich die zwei Schrauben zum Getriebe lassen sich erst im ausgebauten Zustand des Motors wechseln.

What are these two screws supposed to be for, the ones that go "to the transmission"?

And according to the aforementioned statement from ARP, "the head studs can be replaced while the engine is assembled."

Who brings about enlightenment?

Does the transmission need to be removed in order to replace the main bearing bolts of the crankshaft on the AXG five-cylinder TDI engine?

As Michael mentioned in a comment five posts above.
For the two components on the transmission side, the dual-mass flywheel (DMF) needs to be removed, and the engine needs to be taken out.
be separated from the transmission. The ARP in the first sentence forgot to include "almost all".
It's probably just a mistake. *cough*

Best regards,
Micha

I'm just seeing on the T4 forum that it's reported to work even without [something - the context is missing].

Quote:

[...] subsequently, the oil pan must be removed. [...] Only two screws are critical here, as they are located towards the transmission. To remove them, the recess in the flywheel needs to be rotated accordingly. [...] now you can replace the mounting screws.

Kurt.M wrote:

I'm currently seeing on the T4 forum that it's reported to work even without Quote: . [...] anschließend muss die Ölwanne demontiert werden. [...] Kritisch sind hier nur zwei Schrauben in Richtung Getriebe. Zur Demontage muss die Aussparung in der Schwungschreibe entsprechend gedreht werden. [...] jetzt kann man die Schrauben der Lagerung austauschen.

;)Die Aussage betrifft die beiden Schrauben für die Ölwanne am Übergang Motor/Getriebe.

Quote:

You definitely won't be able to remove those two specific screws for the KW suspension. The only way is by using what I call the "brute force" method: essentially, you have to grind away some of the material from the sealing flange in the area where the screw interferes, and then glue the oil pan with sealant afterwards. See a few lines further down for more details.

- It should also be noted that the screws on the bearing, which are located directly next to the transmission, cannot really be loosened. There is not enough space to fit a wrench. However, this tight piece is made of plastic (it's the radial shaft seal or its fixing device), so it won't cause any functional issues if it's modified. Jan said that it should be possible to remove some of the plastic to allow for a wrench to be used. A Dremel can be used very effectively for this, and only minimal modification is required.}

Okay, thank you. If I tell the workshop that, then at least the transmission can stay in place.

But please don't completely ignore the risk that your workshop might not be able to seal the oil pan properly if they remove too much of the sealant. It remains a makeshift solution done at your own risk!

Okay, but what kind of sealing flange is it? Is there a picture available to help understand? Over in the T4 forum, they're talking about a piece of plastic that needs to be removed.

Quote:

The tight-fitting part is made of plastic (it's the radial shaft seal or its fixing device, so there won't be any functional failure due to modification). Jan said it should be easily possible to slightly enlarge the plastic to allow for a nut to be attached. You can very well use a Dremel tool to do this; it really only needs minimal adjustment.

What does that have to do with the oil pan gasket?

Kurt.M wrote:

What does that have to do with the oil pan gasket?

What you need to grind away is the counterpart to the sealing surface of the oil pan.

And is this counterpart to the oil pan's sealing surface made of plastic?

What works shouldn't be changed (or messed with).
If the connecting rod bolts are designed as stretch bolts, and the manufacturer does not specify any requirements for changing them to different bolts (regarding quality or tightening torque), there is no reason to replace them. The bolts were tightened beyond their yield point to achieve a specific preload.
If the torque values for the screws on the KW suspension components are correct, there's no reason to replace them. I would leave those two inaccessible screws as they are in that case. Otherwise, you can make your own tools; a socket wrench doesn't necessarily have to be the right tool for the job.
hg
Herbert.