3.5 efi crank case strong vacuum

hi there everyone i own a 94 discovery 1 with 3.5 efi v8 engine.

i bought it at decent money as it had a badly running poorly serviced engine in it.

once i had found a good engine from a 1989 range rover we set about and checked the 89 engine, checked and cleaned everthing fitted a new 3.9 cam push rods rhodes bleed down lifters steel rockers and rockers shafts oil pump gears true roller timing gear and chain and also had the injectors sent off and cleaned.

i wanted to keep the hotwire injection setup so all we fitted from the 89 engine was the block and heads all the inlet manifold plenium chamber and all sensors came off the original 94 engine,

incidently it was built in 92 not 94 but must have stood somewhere till it was sold hence it being a 3.5 not a 3.9

my problem is now the crank case has started to have a vacuum inside and its using loads of oil, when its ticking over if you remove oil filler cap its trying to suck it back in and the engine slows below normal tick over and picks up again only when the oil filler cap is screwed back in.

this is not a problem i have ever come across before as its the first efi i have owned.

a mate of mine who is used to carbs says it could be a breather or some thing thats blocked. but before i start chasing every thing down to isolate the problem i thought i would ask you guys, any thoughts anyone ??? cheers in advance

the breather hasn't got put on wrong side of throttle body or something stupid like that?
for instance on the servo vat take off.

Can't say I've ever had anything like you describe before

i dont think its a pipe in the wrong place as i photographed them in place before we switched the engines.

i should say that this engine was fitted easter 2009 and has been fine up till a short while back when i noticed it had started to use oil at a high rate.

this problem seems to be head scratcher ive got to know quite a few guys in the landy fraternity over the years and this is a new one to them.

worn bores possibly -a leak down test would confirm this

It's not worn bores etc as you'd have pressure, not vacuum, so it sounds like the engines fine.

The only place the engine can find vacuum is in the inlet manifold. I wonder whether the air intake has been partially blocked and the engine is trying to suck air in through the crankcase breathers? That might explain the poor idle.

Try removing the air filter trunking and running the engine and see if anything changes.

we did check the air filter and it was nice and clean as i changed it when the new engine went in.

i was going to check out the air flow meter next as a precaution.

i do rememeber that i had the air filter detached from the air flow meter once and it didnt run right like that at all.

i will strip it all down from the filter to the plenium chamber and make sure its clear all the way.

As long as it's sucking through the AFM it should run fine without the air filter connected.

Generally, if you unplug the AFM the injection goes into a default mode and the engine runs rich, but I'm not sure that applies to the Rover V8. If it runs better when the AFM is unplugged, you have a bad AFM.

Take a look down the air trunking to make sure nothings blocking it, or the pipes collapsed internally etc. If your Disco is the same as mine, the actual air intake is taking air from a funny gap in the panels in front of the front wheel. It's always struck me as an odd choice. Make sure there aren't any small furry animals stuck up there! Vacuum off a running engine is pretty impressive...

thanks guys i will try out all theories and get back to you.

the vauum from the oil filler cap is so strong that on tick over it sucks your skin in and leaves a red mark, some thing ive never experienced before.

ive haf crankcase pressure before but never a vacuum

I'd agree, sounds like blocked inlet somewhere so drawing air from wherever it can, would also explain it using oil, I don't know much about this engine but, if we're right, I think you'll find a load of oil in the inlet manifold if you take stuff off so you can see in there. Then, with the engine running, I'd take pieces of inlet piipe etc off starting at the end furthest from the engine and see if the engine suddenly breaths a sigh of relief (check pipes over as you go), best of luck.

What's it drive like? I'd assume it's very down on power if the inlet's blocked, if it's drivable at all.....

hi there

right ive stripped down the inlet from the air filter through the afm and the flexi to the plenium chamber all as clean as a whistle no obstructions.

it only runs smooth with the oil filler cap in and every thing connected.

remove afm connector plug and it stops dead.

pull off breather pipe from the left hand rocker cover where it goes into the plenium chamber and it runs rough and the crank case vacuum increases even more.

take air filter off afm and it runs rough.

it seems to be getting the majority of its intake air in from through the crankcase.

im totally baffled it will only run smooth and sweet when sucking its air in through the crankcase.

change any thing that means it has to draw air through the air filter etc and it runs rough which doesnt make any sense as this should put every thing out of kilter because the air flow meter isnt getting a true reading.

with every thing connected as is in normal running it is powerful and runs sweet as a nut, but i must sort it as its using oil at an alarming rate.

any other suggestions will be followed up guys, i have over 600 pounds in this engine i want it to have a long and happy life.

It's a horrible feeling when you spend money on a rig and it runs worse than ever.

I'm really puzzled by "pull off breather pipe from the left hand rocker cover where it goes into the plenium chamber and it runs rough and the crank case vacuum increases even more". You are venting the crankcase to the atmosphere (same as removing the oil filler cap), so vacuum should evaporate. Weird. Running rough, though, should be the lack of vacuum!

If it runs well with everything connected I think the apparent vacuum might be a red herring. If it's using oil, where is it going?

Excess crankcase pressure will be very messy, and removing the oil cap will mean oil is blown out through it. It doesn't sound like it's doing this.

Other than that, oil is being drawn into the bores and burnt. The engine will smoke and possibly 'diesel' - ie run on it's own engine oil, ignoring the throttle.

I wonder if there is a flame trap or valve somewhere in the inlet and crankcase ventilation that is stuck, omitted or leaking? It sounds like the inlet tract is open to the crankcase to excess. It's ages since I had an EFi V8 and I can't remember the layout.

Bear in mind that the ECU is capable of adapting to the engines preferences. Try disconnecting the battery for 30 minutes to get it to forget it's settings (not sure if this works on Land Rovers but it works on BMW's!). Expect it to run a bit rough for 5 or 10 minutes as it finds it's settings after you start it again.

Disconnecting the air filter or anything else that is upstream of the AFM should not make any difference to the engine. I'm still suspicious that somehow the feed to the air filter etc is blocked and it's adapted to running on a different source of air.

hey uncle fes

this really has got me foxed to, when you unscrew the oil filler cap you begin to hear hissing and when it pops out the engine immediatly slows struggles to run and runs very uneven,

if you put your palm over the oil cap and seal it it pulls your skin in and leaves a red mark, when i pulled the pipe off the plenium from the drivers side rocker cover and stuck my hand over the end of the pipe it still ran rough and putting my palm over the oil filler hole at the same time found some great suction my hand came off with a right pop.

some how its finding it easier to draw air from the crankcase to run and my freind who looked at it siad it will be drawing the oil up with it, he said he has heard of diesels doing this that just rev on their own till the oil runs out and they die.

with te oil filler cap off you can tell the air is flowing in but it doesnt like this.

when i took off the air filter from the afm it ran rough as well and putting your hand over its inlet stopped the engine.

putting your hand over the open end of the air filter once its attached back to the afm has no difference you can hardly feel any air flow so i removed the air filter and its clean only done about 2000 miles since new.

it was still drawing a vacuum as well with the afm detached from the air filter.

i despair at this problem as i cant understand what could be wrong.

Have you got a compression tester of any kind? Sounds daft I know but wont cost you anything to try it.

well guys i thought i would update you on the progress and the problem we found. on the plenum chamber right at the front as you look into the engine bay there is outlet/inlet pipe stuck out on the vacuum/inlet side of the butterfly, also across the front of the plenum chamber passes the engine breather pipe to the air intake, some bright spark had attached a t piece (very neatly) to the breather pipe and attachec the pipe coming ou of the plenum chamber.

this meant as soon as the engine was running it was drawing a vacuum through the pipe on the plenum chamber out of the crank case.

this set up was on the original engine and we passed it over not knowing it was wrong.

incidently all i have done with the pipe out of the plenum chamber is screw in a bolt with some gasket sealer on it to seal it up.

does any one know where this pipe is supposed to go, all other pipes are spoken for and correctly placed, is it to do with air con (i dont have this fitted)

after we got all pipes back where they belong we had to reset throttle linkage and timing as well.

thanks for all your help and attention guys. rave on

the lad that sorted it said if it had been a diesel the suction would probably have been enough to suck the oil out of the sump and burn it.

try looking on you tube at engines runnin on their own oil, its not pretty.

NICE ONE!!!

I'd guess the pipe on the plenum chamber is where the breather goes, if there's one either side of the engine thats probably what the T piece was meant to be - one breather split to both sides of the inlet.

i think i know what youre saying, it's like the biggest breather/vacuum pipe there is on the egine.

it goes from the throttle body, to a t piece which goes to the plenum, and then down to the flame arrestor breather (the grey cylinder screwed into drivers rocker cover)

well, this is the same on mine.

mine however runs same with oil cap on or off, and has no major vacuum or pressure at the oil cap if i remember rightly.

the crankcase is supposed to run under slight vacuum though. air goes in at the tiny breather passenger side rear, flows down to the crank and then up the drivers side, and oput of the vacuum breather.

my pipes, breathers/rocker covers were crammed full of sludge, to the point where i expect they were unable to function. this took around 6 hours of cleaning (we did the whole of the inlet system and the rocker covers and rocker areas etc.

i wouldnt recommend simply doing something that makes your engine ok, as it is not supposed to be like that. that t piece is supposed to draw good vacuum from the plenum.

i would be keen to put it back to how it was, but focus on cleaning a hella lot of muck out first.

if you have already done so, then you need to go round working out what makes a difference and what doesnt make a difference, and analyse each reason why.

and find out why the engine would rather draw all its air through a breather pipe than through the inlet.

a good engine WILL run fine with the airflowmeter fitted without an air filter.

check for air leaks in every hose.

check the idle air control round the back of the plenum.

there will be a reason why this is not right.

then you might figure out where all the oil is going.

interestingly my engine has been in its new clean form for a couple of months now, and i have done a few hundred miles in it and various pay n play days, and there is not a spec of oil on the fillerr cap or filler neck. the oil does not spray around in there, so i would find it very unlikely that all the oil is going up the brathers into the throttle.

also, there are trumpets in the plenum so it would be difficult for that amount of presumably liquid oil to make it into the cylinders through the inlet.

hope that helps, sam

p.s. i hope nobody says that the oil should be spraying like crazy in the rockers of a 3.5, cos i guess that means my oilways are badly blocked...

I am assuming this is an idle problem? Does it also run rough (and pull a massive vaccum) at Wide Open Throttle?

Assuming it's mainly an idle issue, then on idle the engine gets air from one of two places,
- air filter ONLY via the Idle Control Valve (Stepper Motor) pipe (not via the butterfly)
- Crankcase, via the breathers; yours are connected correctly via the t-piece.

It does not get air from the butterfly, cos it's closed.

If there is a massive vacuum in the crankcase, then it can't be getting any air from the Stepper Motor Brether pipe.

Therefore, it is only getting air from the crackcase breather.

So, my bet is on a dodgy stepper motor. And, I bet the previous owner sorted this by adjusting the idle tick over screw, which is on the thottle body section of the plenum.

Jim

Very clever analysis Jim, good detective skills!

That would explain why it's sucking so much through the crankcase!

The only place vacuum can come from is the inlet manifold. That small pipe to the plenum chamber is not going to cause that much vacuum as there is a pipe on the left tappet cover on the left that should be letting air into the crankcase. Also the larger section of pipe that the little one connects to may go to the crank case breather, but the other end of it goes to the airfilter side of the throttle butterfly. It is much easier to suck the air it needs from the airfilter than to create vacuum in the crankcase. My suggestion would be that your intake manifold is not sitting properly on the heads and the engine is sucking air directly from the valley of the motor.