Intake manifold removal M42 1990 318is

[Mark James]

Hi, Just wondering if anyone knows how difficult it is to remove the intake manifold? I have a fuel leak (steady drip when engine is cold, then leak disappears when engine is warm) coming from under the intake manifold, so I have bought o rings for the FPR , fuel hoses and an o ring for the fuel injector. I am thinking that replacing all of the above will fix the fuel leak?
Also, I am going to need a gasket for the intake manifold. I've noticed there are 2 gaskets (on the diagrams) Do I have to get both of them or just one? If so, which one?
I've done basic servicing and bodywork before but never attempted anything like this!

[monty23psk]

normally the leak is at the 2 small 2-3in hoses from the gas tank to the fuel rail, the to and return pipes. they dry out over time. I believe you can get to them by just removing the upper intake manifold, so you only need those paper gaskets. Everything else you got is great for a complete overhaul but might not be required.

[1998ccc]

The hose you need is 8x13.  Buy the good stuff.  You will also need two new hose clamps if your car had the recall done....BMW used a tamper proof style clamp.

[Mark James]

normally the leak is at the 2 small 2-3in hoses from the gas tank to the fuel rail, the to and return pipes. they dry out over time. I believe you can get to them by just removing the upper intake manifold, so you only need those paper gaskets. Everything else you got is great for a complete overhaul but might not be required.

Great, thanks for your reply. Do I need to replace 2 gaskets on the upper intake manifold? (Numbers 10 and 11 on the diagram) or just number 10?
Its hard to tell where number 11 goes to a novice like me!

[colin86325]

You should need to replace only part 10. (part 11 goes between the cylinder head and the lower part of the intake.)

[Mark James]

Excellent, thank you very much!

[DesktopDave]

Just a few things off the top of my head...I don't want to sound pedantic so ignore anything you already know. It's not that hard, but I recall having the same anxiety when I pulled mine apart the first time.

I like to use a penetrating oil like PB Blaster or even WD40 to make disassembly easier.
You'll only need to replace the middle gasket, as mentioned. You likely won't need to disconnect the throttle cable, just put a rag on your windshield and rest the intake up there.
Once you get the manifold apart, stuff two shop rags/t-shirts/paper towels into the intake tubes. Dropping a washer or nut into the lower intake isn't a lot of fun.
I like to use a single-edge razor blade to remove what's left of the paper gasket but a gasket scraper might be a better idea since the steel blade will easily scratch the manifold surface.
The gaskets are only thick paper, you'll put them on dry. They don't have a top & bottom, ignore any printing. I avoid silicone RTV (make-a-gasket) whenever possible unless recommended by the manufacturer.
Be sure when you reassemble the manifold that you set the upper part onto the locating dowels properly before you start to tighten fasteners. There are two of them, part #6 on the drawing. Kudos for getting into RealOEM, BTW!
After you have the upper manifold pre-assembled onto the dowels properly, tighten the fasteners in steps...like get them all hand-tight, then go ever them all again with a ratchet wrench to do the final tightening. They are small fasteners, you won't need much strength to tighten them properly. I believe the spec for high-strength M7 & M8 fasteners (like those on the upper manifold) is only about 15 foot-pounds. Measure your wrench & estimate the force. A 12" long wrench will only require 15 pounds at the end of the handle to properly secure the fasteners.

I know that the bolts use 10, 12 & 13 mm heads, but all metric fasteners are designated by the thickness of the threaded portion. Once you're done with this job...you'll be ready to head on under the car to loc-tite the upper oil pan bolts!

[Mark James]

Just a few things off the top of my head...I don't want to sound pedantic so ignore anything you already know. It's not that hard, but I recall having the same anxiety when I pulled mine apart the first time.

I like to use a penetrating oil like PB Blaster or even WD40 to make disassembly easier.
You'll only need to replace the middle gasket, as mentioned. You likely won't need to disconnect the throttle cable, just put a rag on your windshield and rest the intake up there.
Once you get the manifold apart, stuff two shop rags/t-shirts/paper towels into the intake tubes. Dropping a washer or nut into the lower intake isn't a lot of fun.
I like to use a single-edge razor blade to remove what's left of the paper gasket but a gasket scraper might be a better idea since the steel blade will easily scratch the manifold surface.
The gaskets are only thick paper, you'll put them on dry. They don't have a top & bottom, ignore any printing. I avoid silicone RTV (make-a-gasket) whenever possible unless recommended by the manufacturer.
Be sure when you reassemble the manifold that you set the upper part onto the locating dowels properly before you start to tighten fasteners. There are two of them, part #6 on the drawing. Kudos for getting into RealOEM, BTW!
After you have the upper manifold pre-assembled onto the dowels properly, tighten the fasteners in steps...like get them all hand-tight, then go ever them all again with a ratchet wrench to do the final tightening. They are small fasteners, you won't need much strength to tighten them properly. I believe the spec for high-strength M7 & M8 fasteners (like those on the upper manifold) is only about 15 foot-pounds. Measure your wrench & estimate the force. A 12" long wrench will only require 15 pounds at the end of the handle to properly secure the fasteners.

I know that the bolts use 10, 12 & 13 mm heads, but all metric fasteners are designated by the thickness of the threaded portion. Once you're done with this job...you'll be ready to head on under the car to loc-tite the upper oil pan bolts!

Great, many thanks for your detailed reply. There is little or no information or advice wasted on me! Hopefully, the leak is coming from the fuel hoses, but I do have O rings for fuel injector and FPR as I've heard that fuel leaks can also be caused by corroded O rings.
I do also have a small oil leak, so I guess tightening up the oil pan bolts underneath the car would be a good idea for this?
Gasket will be in the post today, for delivery tomorrow, so I will attempt the work then!

[DesktopDave]

The oil leak is most likely from the o-ring & gasket at the oil filter housing. It tends to leak down the side of the block and around the lower pan. Replacing that gasket & o-ring is a little more involved than the intake. The intake & alternator both need to be removed, which means disconnecting the battery. You might as well do the oil pan and an oil change all at the same time.

Dropping the lower oil pan to check those upper pan bolts is for an entirely different reason. It's probably already been done to your car so don't worry too much. It's recommended to check for this sooner rather than later...maybe during your next oil change? Here's why: the upper bolts tend to work loose over the years due to vibration. This will cause the upper pan gasket to fail at the primary oil pump feed passage. That's pretty bad....the oil pump stops supplying oil to the engine, and is rapidly fatal to the cams & main bearings. Those are very small M8 bolts and can't take much torque. We've always recommended using a thread locking compound such as Loctite Red to prevent this from happening. Speak of the devil...here's a fresh post about that very problem!

Do you have any history on the car? It'll save you a bunch of work if you know what's been done over the decades. Once you've chased down all the vac leaks, checked the upper pan bolts, sealed up any pressure leaks in the cooling system, these engines will last for a LOOONG time. Mine's been parked for a while, but it's done 293K or so miles on the original motor without any overhaul whatsoever. Previous owners had done significant work on the car over the years...I was tremendously lucky to get almost every service receipt along with the car...it came to $10.5K worth of work having been done since the car was delivered to the customer on Oct. 27, 1990.

[Mark James]

Thanks again for your detailed reply Dave. I ordered the fuel hose and o rings for the FPR but the company I ordered from sent the wrong parts :-/
So, need to sort that first.
I don't have any history for the car, but have had it for 6 years and it's been mechanically sound up until now. I had the pinion bearings changed about 4 years ago, fuel pump about 3 years ago and water pump about a year ago. I love it and now want to try and work out how to repair most things mechanically.