740 Turbo crankshaft

Albert

Hi, hoping someone can give me some advice….my son has a 1991 740 turbo which has a damaged crankshaft due to a loose front pulley. Can anyone give me a definitive answer on whether the turbo, non turbo and 240 crankshafts are the same? Can anyone suggest where I can purchase one? Many thanks

GingerNinja

I thought it was the pistons that were different. As long as you get a later model crank like the one you have. Maybe 1990 onwards but hopefully someone else will chime in about the dates.

jamesinc

They're not all the same, the B21/23 crank is different to the B230 crank. There are two types of B230 crank, mid thrust bearing, and rear thrust bearing, you'll need the right one for your motor.

Otherwise they are interchangeable NA and turbo.

Major Ledfoot

Crankshaft p/n 1378980 fits all redblocks with 80mm stroke and 63mm main bearings with rear thrust.
Thus K and L blocks use the same crank, even if early production K block engines from 1988 use the weak 8mm rods.

ramrod

Are you sure the damage cannot be repaired?

Changing a crankshaft is a BIG job, easier to replace the whole engine

Maybe show a picture for a better understanding of what has happened

Albert

ramrod There is too much material missing from the front of the crankshaft to attach the pulley correctly. Apart from this the engine is in very good condition and I am reluctant to replace it with one of unknown quality. Either way the engine has to come out.

ramrod

So what’s actually damaged, the front of the crank, the crank pulley gear (for the belt) or the harmonic balancer

it most probably can be fixed

Show a picture if you can

Albert

It's all a bit complicated, the car is in Canberra and I am in Ballarat Vic. It is at a workshop that specialises in Volvos and they are telling me that the front of the crankshaft is damaged and cannot be repaired. They are willing to replace it if I can source one as they are not prepared to spend time searching.

ramrod

Get your car back and fix it yourself.

Don’t support those that refuse to support you

Spac

Which workshop?
Ike’s is the only Volvo Specialist who are actually Volvo specialists.

I imagine that the harmonic balancer has come loose and the grooves on the end face of the crank that locate the balancer have flogged out.

Just to reiterate what James said, there’s three possible cranks, although the first of the three is not going to be an option in a 740T unless it has had an engine swap.

The B21/B23 crank has big bearings for the main and rod bearings.
The early B230 crank has small main and rod bearings.
The late B230 crank has big main bearings and small rod bearings.

Albert

It would appear to be the late one then and there's not likely to be many of them knocking about, I wonder if repairing is possible.

ramrod

The harmonic balancer doesn’t contact the crankshaft.

it rests against the crankshaft gear pulley.

Does the mechanic know this or are they being complacent, not bothering to actually spend more than twenty seconds diagnosing the issue?

Albert

ramrod It is the crankshaft pulley that had been loose.

Spac

If you can confirm which one you need, then I am sure you’ll be able to find what you want.

It is definitely repairable, but we live in a world where nobody wants to repair things, and it is easier to just replace… they probably don’t want to have the replacement part on hand so the whole process is quicker and easier for them.
Lots of mechanics have no awareness of what can be repaired anymore, too.

I would be asking them how much they will be charging too. It’s not a small job - there’s a few different ways to do it, but they are all time consuming.

Albert

Spac Definitely expensive whichever way you go.

ramrod

Albert

I understand what you’re tying to explain.

So that we are 100% totally clear on what we’re talking about, there are two pulleys.

The pulley on the OUTSIDE of the engine, aka harmonic balancer. You can see this by looking at the bottom front of the engine. It turns the drive belts (alternator, water pump, power steering, air conditioning).

The pulley on the INSIDE of the engine, aka crankshaft gear pulley, is behind the harmonic balancer and drives the cam belt and you cannot see it unless you remove the harmonic balancer.

If the pulley on the inside is damaged, it is removable and replaceable for a couple of hundred dollars. It should not have done any damage to the crankshaft.

That’s why it would be ideal to see pictures showing where in fact the actual damage is

Albert

They told me they removed the harmonic balancer then found that the bolt holding the crankshaft pulley was loose and the pulley had been moving around which had chewed up the end of the crankshaft, I should imagine where the two surfaces mate.

ramrod

Ask for pictures (evidence)

jamesinc

I've had this happen, you can see here what a loose harmonic balancer does https://ozvolvo.org/d/11590-11590/36

I didn't have to replace the crank though, or the pulley for that matter, I just filed the damage off and put a new crank pulley on it.

Spac

Which workshop is it at?