156.net saved thread - 166 3.0 V6 teardown - Sept 2007 - Alfa Romeo Forum
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156.net saved thread - 166 3.0 V6 teardown - Sept 2007

As some of you might know, the 156.net forum is no more. We knew that the site was going down for a while (lack of traffic) so I took the opportunity to save some of my (hopefully) useful threads.

Bought a broken 3.0 V6 and a good gearbox out of a 166 last Friday. Spent my day off work removing it, some of Satuday stripping the ancilleries off (not included in the sale) and Sunday Mounting it on a stand. I started to strip it down last night after work....







Removing the gearbox. The V6 uses a pull clutch so you must remove the slave cylinder prior to trying to pull the box off the engine.





Unfortunatley, the starter motor needs to be removed and to get at one of the bolts holding it in place (circled yellow) you need to remove the rear exhaust manifold which is a real pita in car.



Clutch removed to show DM flywheel.



The 166 engine mounts are very different to the 156 set up, as is the subframe. On a 166 it forms a complete square around the engine, with the front mounts bolted to it rather than the chassis legs ala 156 Its also more difficult to remove the engine as a result.



In order to remove the mid drive shaft you need to remove the 3 bots holding it in the mount:



Putting the engine on a stand:





Removing the cam belt covers. I rounded off the hex head bolt circled red... [:$]



Removing the rounded bolt. The splined socket shown is fantastic for removing them pesky rounded off bolts.



Covers removed:



Stripping the wiring loom off the front bank:

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Treacle tart and tesco finest custard!!!!!!



Removing the plenum chamber. Its suprising how much stuff you DON'T need to unbolt off it:



Its bolted to the cam over via the two hex bolts arrowed:



Removing the wiring loom to the plugs and injectors:



Ping it off with a flat blade screwdriver, just make sure you keep a finger covering it otherwise it really will "ping" off!



Injectors - green
Coil packs - red
Multi plug that lives by thermostat - yellow
Earth lead to cam cover - magenta



The intake plenum sits on several rubber bushes and they nearly always go awol. There are 4 on the plenum itself and an additional 2 on the cam cover.



Plug holes. I've put all of the loose bolts back in their respective positions. Some are longer than others and it avoids confusion.



Removing the sump. The bolts circled green hold the heat shield on over the crank sensor. The sump is held on with 11mm bolts for some bizzare reason.







Remove heat shield.



Crank sensor circled cyan. You don't need to remove it, Just release the wiring all the way up to the connector.

Remove bolts circled red.



It was at this point I started to attack it with a crow bar, not realising I had missed one hidden bolt:



Bugger!!!! To get at it you have to release the rear mount and oil filter housing. This engine is out of a 166 remember, other cars will be different.

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Problem is the cast alloy plate that the alternator bolts to fouls the oil filter housing. If you unbolt the housing you should be able to get enough clearence to get at the sump bolt without removeing the alternator mount. Handy if engine is still in car. I just removed both.



remove sump....

.... and oh dear. [xx(] That's a lot of metal on the pick up...



and in the sump....



Just one bearing had failed and spun on the crank within the conrod. Both are fubar. Engine is not an economical repair.





Oh well. []


I stripped the engine down a bit more last night. Shown here with the cam covers and intake pipes removed.
I did NOT use cam locks when stripping the engine as I have no intention of rebuilding it, I do have some but I couldn’t be arsed fitting them. I would advise that anyone considering changing the cam belt on a V6 should use cam locks.



Arrowed Green – Idler pullies, should be replaced with cam belt.
Arrowed Red – Tensioner, should be replaced with cam belt.
Arrowed Cyan – Water Pump, should be replaced with cam belt.
Arrowed Black – Cam belt pullies.



The cam belt pullies are held on with a 19mm bolt which fastens and locks them onto the camshaft via a taper lock.
When changing the cam belt I have seen some people attempt to “lock” the cam shaft via the cam locks. This is a MISTAKE! You use the cam bearing cap bolts to fasten them in place and they are not strong enough to withstand the torque generated when undoing the pully bolt. You tend to end up with a stripped thread for the bearing cap bolt.

Not good. Head off, and a complete rebuild required. I use this tool (below) to hold the camshaft. Its very awkward to get it onto the rear bank pullies in car but not impossible.







Dial guage, used to find TDC



Cam belt tensioner. As I have said before, if you’re changing the cam belt you would be mad not to re-new this as well. Its critical to the well being of the engine….

It rotates about the socket bolt circled and you nip up the bolt out of sight (arrowed) when the correct tension is achieved.



I’ve always struggled to tension the belts on V6’s as I have always replaced the plastic impellor pump with a metal type. But not the genuine GTV pump from Alfa, nooo cheapskate here tends to favour the pattern equivalent. There isn’t a great deal wrong with them, they’re good quality AFAIK, the only problem is they are slightly different externally and you can’t fit the tool to tension the belt on them. I eventually found the solution – Stillsons.

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Cam belt removed. If you look at prev pics and compare it with this one, it should be obvious why the water pump can only be replaced by removing the cam belt.



Cam Pullies and cam shafts. The cam shafts for have a groove cut into the ends but its not keyed to the pully. The inside of the pully is completely smooth. It makes tension the cam belt a doodle but start up time is a bit nerve wracking. If you don’t torque the cam pully bolts up enough, the cam pullies don’t lock onto the camshaft and valves get chewed.





Another problem I have encountered working on these engines is with the idler pullies. The hex head bolt that holds them in place for some reason is always fecking tight. I think they’re put in with thread lock pus with the bolt being steel going into an alloy casting you get the usual corrosion issues despite the bolt being the plated type. 50% of the time I’ve found myself rounding the head off rather than undoing it.

There are two methods of extraction worth trying. The splined sock has been shown in my first post, the other method worth trying is to smack a suitably sized socket over the head of the bolt.

To gain access to the lower pully in car on a 156 you have to drop it off the offside front engine mount. I don’t know what access is like on a 166.

Its much easier to gain access to the top (mid) pully as you can remove the section of engine its bolted to quite
Easily…. Remove the section held on with the nuts circled green. You may to remove the shield 1st, I can’t remember TBH. Its held on via the bolts circled cyan.





Water Pump removed from the engine block. 12x 10mm bolts.





The WP itself. On first glance it looks OK:





Closer inspection however revealed slight signs of failiure. I don’t know how many miles the engine had done of if the pump had been replaced at any time.



The pipe shown in this picture runs to the thermostat. I’ve had problems with these before. They have rubber o rings that seal it at either end into the water pump and the stat. They don’t always seal properly and can leak, sometimes profusely. Problem is you cannot remove them without taking the engine out or one of the heads off. A smear of silicone grease should help it seal if you do have problems with it.





Pics of the cam shaft position sensor. Unlike t sparks they are not in a vulnerable position and generally don’t cause any trouble.



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And finally a pic of the chain drive to the oil pump.





Thermostat removed, the wiring for a knock sensor is in the vee. There are two knock sensors, if either fails its going to be a bit of a problem as they’re buried under the solid pipe I’ve mentioned previously, the one that runs from the wp to the stat. To remove it you’d have to take the head off the front bank.



I’ve labeled the next two pics as the way alfa sees them. The front bank is the left hand bank, and the rear right hand, obviously. In the first pic there is “SX” cast into it. S standing for Sin, Sinister….. left handed. It’s a roman thing I believe. The rear bank has “DX” cast into it in the same place, standing for Dextra IIRC. Sorry if I’ve spelt any of that incorrectly…

Then in the second pic you have Alfa’s method of numbering the cylinders. This is all great and works fine if you use genuine cam locks as everything ties in: e-learn instructions, the makings on the engine and the markings on the cam locks.

The problem I’ve found is the Cam locks for the 2.5/3.0 I have, taskmaster I think, are labeled entirely differently and it all gets a bit confusing.

Either way TDC is found on no 1 as labled in the pics. The camlocks go on inlet and exhaust on no 1, inlet on 6 and exhaust on 4.

Also if you look closely at the first pic you can see the cam bearing caps are marked. The have a number and an arrow so that know which is which. They are marked numerically on the front bank and alphabetically on the rear bank. Who ever did the last cambelt change on this engine wasn’t paying attention as the bearing caps marked 4 and 7, i.e. the ones you remove to put the cam locks on, were switched.

The numbers in perm marker relate to the sequence for the head bolts. I don’t think it’s that critical when you’re undoing them.





Some pics with the heads off:







Going back to the bottom end. Oil pump removal. Three bolts and its loose. Having removed it I would suggest you leave the bolts till last as the cog that drives it is on a taper lock and having the pump flapping about loose doesn’t aid the removal process.



You the need to remove the front section off the engine to remove the pump. The Cam belt drive pully just slides off. Its not locked to anything and comes off with the front of the engine. I swore at it and used a crow bar.



Front crankshaft oil seal, highlighted pink.



Chain drive for the oil pump.



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Before removing it you need to remove the key on the crank shaft like so:
(Crap pic I know….)



There is no need to break the chain. It just slides off. Again, I used a crow bar and harsh language.



Pump removed, main bearing cap bolts highlighted.





Main bearing caps removed.






Front bank. In the process of detaching the con rods from the crank. I had unbolted the 2 bolts holding the rod together tapped the end of the con rod loose and the piston and liner fell out onto the floor….



You’re supposed to lock the liners in place. Like so (Pics taken from another rebuild thread)

I used a big washer - 13mm ID, a 90mm length of tube another washer and the head nut. The middle liner isn't close enough to a head bolt for this to work so in this instance I trapped a flat steel bar uder the washers to hold it down.







Crank shaft removed:





Pistons removed, shown in order. The piston and rod highlighted pink is the one that failed. Number 5.





Oil cooling jet aimed at the bottom of the piston



And a garage full of bits.

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