'90 535ia head gasket went south

[Dash01]

How much extra trouble is it to replace the timing chain, sprocket(s), and tensioners while the head is off for HG replacement?

How about the oil pump?

Most important questions:

1. If the head is overheated due to a blown HG, what are the chances that it will need to be resurfaced? (Need to make a decision on what thickness gasket to buy, hopefully without having to wait for head inspection)

2. Can the oil pump be rebuilt with new internals (i.e., whatever wears out replaced), or is a whole new pump required?

[535ise]

To replace the chain and guides you have to remove the lower timing cover which means you need to remove the vibration damper and hub. The big hub nut can be a pita depending if you have the right tools as it's VERY TIGHT !

You need a 3/4 drive breaker bar, matching socket with a big tube to slip over the breaker bar handle for extra leverage or a decent air wrench type thing.

Once the nut is off you will need a hub puller, you might be lucky and just be able to pull/gently lever the hub off but all bar one out of four hubs i've had off needed a puller.

The timing chain guides and the oil chain tensioner are just held on by some little circlips so come off easily.

Cam sprocket is easy as it just bolts on but the crank sprocket is heat expanded on to the end of the crank, i've never replaced one so i'll let some one else help you with that.

Oil pump change will need the sump to be removed(or lowered out of the way ?), once the sumps off it's fairly easy to swap pumps. The oil pump is not re-buildable as far as i know ?

I would get the head checked out properly by an engineering shop, explain whats happened and see what they advise. It's going to be hard to decide about which head gasket to use till you know what state it's in ?

[Jeff N.]

Good advice.

Dash, let me know if you decide to do the entire lower front end. I've done a couple lower crank sprokets (admittedly never with the block in the car) and am familiar with removal and assembly.

Also, if the head is overheated and sprung, normally they don't prefer to shave it. Instead, they'll disassemble and heat it in an oven and then straighten it out.

[Dash01]

Thanks, guys, that's really good info to have, especially about the re-cook of the head rather than resurfacing. Any idea ~how much that costs?

And, regarding the timing chain guides: To remove the old one and replace it, is it still necessary to remove the lower TC cover. Or, can it be slipped out/in from the top with just the upper cover off?

[535ise]

And, regarding the timing chain guides: To remove the old one and replace it, is it still necessary to remove the lower TC cover. Or, can it be slipped out/in from the top with just the upper cover off?

The lower cover has got to come off unfortunately :(