seized engine advice please

[stemid 0]

I bought a rado vr6 with a seized engine a few months ago. As a quick fix I bought a replacement engine and got it going and it's awesome :D

 

Yesterday I had a spare half hour, so thought I'd have a look at the old engine to see why it seized.

 

Just for the record, I have never delved into an engine block before, so I am a complete noob and some of my terminology may be wrong. But I am trying :wink:

 

As they say a picture is worth a thousand words, so here's what I found

 

 

 

 

 

The shell of the second crankshaft bearing was completely scored up. As soon as i took it out the engine would turn over lovely by hand.

 

Now my question, as a noob, is what would cause this?

 

The previous owner told me the oild light/buzzer came on, so he took it to a garage where whilst investigating it, the engine went tight. He told me the car was never driven since this point. And to be honest I believe him, as the crankshaft looks to be in good nick. I don't think it has scored it.

 

Secondly, to fix this, is itjust a case of new shells and away we go?

 

Help appreciated, this is one big learning curve :salute:

 

Steve

[VR6 0]

Fair play for giving it a crack :salute:

[mikkijayne 0]

Are they all trashed or just #2? It looks like it has lost oil pressure for whatever reason, and that journal has overheated and picked up the bearing shells.

 

I would look carefully at the cams and the other bearings and see if there is any more damage, as its likely whatever has caused the loss of oil pressure has had some other effects as well. Check the oil pump, oil cooler, etc.

 

It could be that it spun that bearing first and that was the cause of the loss of oil pressure. I have heard of VR6s spinning bearings, but I don't know why they would do that in the first place without some other cause.

 

Hello from Crediton :wave:

[fla 9]

yep looks like oil starvation. The crank would need serious amount of punishment to get scored, the bearing shells are there for just that reaspn, to be the 'wear point'. I would change them, making sure that the new shells are properly fitted and oiled. When you do fit them in, make sure you line them up properly. Oil them nicely before fitting. I was advised that grease is not a good idea here.

There is an oil feed groove in the shell so gently press this into the oil feeder point. Also make sure that the shells are central axially. It will be obvious, as you've already taken it apart. Bolts can also be reused, unless they've already been off a few times and have stretched. You seem pretty clued up so i dont think you'll have any issues. :wink:

[mikkijayne 0]

Bolts can also be reused, unless they've already been off a few times and have stretched.

 

Torque specs for con rod and main cap bolts are all torque plus angle which means they are stretched on first installation - mains by 180* and rods by 90*, plus VW says to renew them. I would renew them myself for peace of mind. Mains for an ABV are N903 658 01 and are only £1 each from VW. Rod bolts (077 107 425B) are rather more at £8 each :pale: You might be able to get them from an engine builder though if you ring around.

 

Not sure if you could replace the main bearings on a VR without removing the crank completely? You certainly could on a 4-cylinder, but then if it were me I'd want to inspect and probably renew the rod bearings as well anyway after a failure like that.

 

:cat:

[stemid 0]

thanks for the replys guys, and hello mikkijayne, good to see a local onboard :)

 

i started by taking the conrod bearings out, and they all looked ok, so i then moved onto the mains, and got as far as number 2 which was fooked. havent's taken the rest off. i think i will though because i'll probably take the crank out to give it a polish on the one that failed. is it possible to remove the crank without disturbing the upper chains? don't really want to lose all the timing.

 

can someone tell me what a journal is, is it the groove in the shell which lets the oil pass, or is it the hole in the crank? also where does the oil come from in that hole? i can't see anywhere that oil is pumped into the inside of the crank?

 

it would seem that oil has been starved to that shell, but if the oil pump was nackered, wouldn't the all be trashed?

 

is there any way of testing an oil pump?

[Pickard1 0]

Hi,

oil starvation would normally result in the shells becoming very hot and therefore ending up discolored and blue. It is possible that you have a case of oil starvation and you just caught it in the very early stages. The oil light coming on would support this, but then it can be a bit of a chicken and egg situation, 'cause once the crank seizes and the tolerances between the crank and bearings become knackered you are likely to get oil pressure problems.

I don't know the exact ins and outs of this engine design, but I would have thought that if one of the mains were to go from oil starvation it would be one of the end ones (main 1 or main 7) as one of these would likely to be fed last.

 

The cap side shell in particular shows some edge loading. If it were a new engine or a newly rebuilt engine I might suspect an alignment issue.

 

When you strip the other shells you should learn more. If they are all on the verge of breaking down then it probably was straight oil starvation.

 

I was quite surprised to hear the big end shells were ok, I would have thought one at least would be fed by that main journal and would have picked up all of the debris from the seizure.

 

have fun!

[mikkijayne 0]

 

can someone tell me what a journal is, is it the groove in the shell which lets the oil pass, or is it the hole in the crank? also where does the oil come from in that hole? i can't see anywhere that oil is pumped into the inside of the crank?

 

Journals are the machined parts of the crank that the bearings run on, so you have two sorts - one for the main bearings in the block, and one for the connecting rods.

 

The oil is fed from the pump down drilled galleries in the block to each main bearing. The groove in the shell allows oil to flow around the bearing and in to a drilling in the crank which then feeds the oil to the conrod bearings.

 

Here's a rather handy pic that Google found for me:

 

 

The red arrow is pointing to a conrod journal. If you look at the two main journals on the left you can see the oil drillings there, and also on the two rod journals in the middle. Looking at the angles of the holes it seems that each main feeds the rod to its right in that picture.

 

Tracking down a failure on a single bearing is tricky, especially if all the rod bearings are still good. It could simply be that the oil pressure was low and that bearing got picked up and spun around the crank, but the others just managed to hang in until it stopped. I'd have a good look at the oil pump to make sure that is still intact and within tolerances, and also blow all the oil galleries out with an air line to make sure there aren't any blockages anywhere.

[stemid 0]

ah thanks for clearing that one up. starting to learn the terminology of these parts now :)

 

managed to get another 1/2 hour to look at it today. took the rest of the main bearings off and found the following

#1 just beginning to fail

#2 (pictured) the worse shell

#3 almost as bad as #2

#4 not quite as bad as #3

#5 again, just on the verge of failing

#6 & #7 perfect condition, look brand new!

 

so this is more pointing towards a loss in oil pressure, as 5 out of the 7 shells have started to break up. with #'s 2,3 and 4 being the starting point

 

now i need to decide if it's economic to replace all parts necessary, these being main shells, conrod shells, conrod bolts, and possibly oil pump? any idea on a rough price? or do i just scrap the engine? :confused4:

 

on a positive note though, the timing chains look in great condition, especially for a 160,000 mile engine :clap: i guess the must have been swapped at some point

[mikkijayne 0]

Given that you can buy a running VR6 for £200 or so I'd say by any normal standards its toast.

 

The only way I would consider this worth rebuilding is if you were planning on keeping the car forever and wanted to invest in a 'new' engine, by which I mean replace everything including honing the block, new rings, etc. Or, use it as a donor to build a mad turbo motor :D

 

For a normal runabout / weekend car I doubt it would be worth the cost.

 

:cat:

[stemid 0]

ha yeah well it's funny you mention 'turbo'......

 

i think i may go down that road with this engine sometime,

 

watch this space....

 

p.s does this look like a good deal?

http://cgi.ebay.co.uk/TURBO-KIT-ALL-VOLKSWAGEN-VR6-VW-BRAND-NEW-KIT-/170346524761?cmd=ViewItem&pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item27a971b059