finding vacuum leaks

clubman_dan · Post by **clubman_dan** » Mon May 21, 2007 8:03 pm

i have noticed that at idle my boost gauge hovers above the -14 mark, indicating that i must have a vacuum leak somewhere.
i have just spent a while today changing all the old cloth wrapped hoses for new silicone ones.
i was hoping this would solve it, especially since the ones connected to the fuel evap unit were really nasty at the ends.
however the leak remains, i have also removed and checked the one way valve for the oil breather, i can blow and suck through the larger pipe, and i can suck, but not blow into the smaller one (i think thats ok?)
any other ideas for things that i could check?
cheers
Dan

pol · Post by **pol** » Mon May 21, 2007 8:53 pm

The valve next to the oil breather..... Is shit.... Check it in much the same way. Also suck the vacuum hoses. I had this problem. Removed the valves for some simpler design...

pol

clubman_dan · Post by **clubman_dan** » Mon May 21, 2007 9:05 pm

do you mean the one that is covered in foam and sits on it? thats the one i have checked. or is there another one which i havent seen?

rpruen · Post by **rpruen** » Tue May 22, 2007 1:07 pm

Vaccum leaks can happen anywhere. Any pipe between the MAF and the throttle body being split or broken will make the car run lean, giving a poor vaccum reading. The intercooler tends to leak at the bottom where water sits in the crimped part near the end tank.

There are more of those cloth pipe joins inside the car, near the ECU there is a 'T' that splits the pipe in two. One to the ECU, the other to the boost gauge.

Try the manifold gasket that holds the two sections of intake manifold together. The bolts tend to strip if overtightened, and can lead to leaks.

Another point to check is the intake/exhaust gasket. A total pain to get to the nuts, but can be done with a 1/4 drive socket set. The nuts tend to work loose due to heating / cooling cycles. I have found many engines where at least one has dropped off. They are 'special' nuts, and also have a thick washer under them.

Test for leaks by spraying easy start down the back of the injectors onto the intake manifold. Do this with the engine cold as you can't help but spray the exhaust manifold too. A change in engine note indicates a leak, a flame, a leak on the exhaust side.

If doing the nuts up a bit doesn't help, then removing the manifolds to replace the gasket is the only option.

I think that just about covers everything.

Richard

piper1st · Post by **piper1st** » Tue May 22, 2007 1:33 pm

rpruen wrote:I think that just about covers everything.

Almost Rich ...

This happened to me last year ... see thread here!

Here's a pic of what my boost gauge was reading ...

Only the problem was simply ... the gauge was faulty! Try that too!

rpruen · Post by **rpruen** » Tue May 22, 2007 2:07 pm

piper1st wrote:Almost Rich ...

Only the problem was simply ... the gauge was faulty! Try that too!

Ok I'll give you that one...

That's the only one I have seen to go wrong, and I have subjected boost gauges to some serious abuse (like 28 psi or so).

Richard

clubman_dan · Post by **clubman_dan** » Tue May 22, 2007 2:21 pm

thanks for the replies.
i am sure the gauge is funtioning ok, because the needle will go down to -14 if you lightly press the throttle, also since i have changed the hoses it now sits at -14 most of the time when warm, however when cold it will sit about halfway in to the white section. i do have a spare gauge set though so i guess its worth a try.
i will check the inlet manifold and report back.
cheers
Dan

JohnTurbo · Post by **JohnTurbo** » Tue May 22, 2007 2:21 pm

In this case i think you do have a vacuum leak though - The lumpy idle is the tell-tale.

clubman_dan · Post by **clubman_dan** » Tue May 22, 2007 9:07 pm

yeah! if only it was just the gauge lol! worth a check though in case a miracle happens

martinholmesuk · Post by **martinholmesuk** » Tue May 22, 2007 9:53 pm

My gauge shows to much pressure. How do I fix this?

pol · Post by **pol** » Wed May 23, 2007 8:41 am

Home come your digi clock is red martin? Did you change the colour?

My manifold gaskets were a big problem at one point.
Also my bottom intercooler hose, and the breather valves.

pol

Agwa Moose · Post by **Agwa Moose** » Wed May 23, 2007 9:24 am

martinholmesuk wrote: My gauge shows to much pressure. How do I fix this?

First off you need to decide how much pressure you would like it to show

Once you've decided this drill a small hole in the gauge face at the point you have decided on then glue a small peg into the hole - when your gauge rises the needle will now hit the peg and stop instead of going all the way up

Problem solved

Alternatively you could just disconnect the gauge, that'd work as well

J

robkendall · Post by **robkendall** » Thu May 24, 2007 6:56 am

martinholmesuk wrote:My gauge shows to much pressure. How do I fix this?

photoshop the needle in a different place next time

rob

98kellrs · Post by **98kellrs** » Thu May 24, 2007 10:06 am

martinholmesuk wrote:My gauge shows to much pressure. How do I fix this?

There's such a thing as too much boost?

clubman_dan · Post by **clubman_dan** » Thu May 24, 2007 4:32 pm

checked the manifold, and one of the nuts has fallen off, obviously the problem lies here. i have slung a nut on there from the old car and tightened, hasn't really made any difference, not surprising really though.
does anyone have any part numbers for the gasket? i went to volvo and its about Ã‚Â£32! even the guy on the parts desk thought that was a bit steep.
and i tried a couple of motor factors who told me that its dealer only.
there must be a cheaper alternative!
not looking forward to doing this! looks pretty tight for clearance back there..
cheers
Dan

catgroom · Post by **catgroom** » Thu May 24, 2007 6:32 pm

@Pol Mate,you just take the green film strip out of the clock then you actually read it!!

You can do the same with the infocentre too,but its a hoe of a job,unless youre dexterous.In which case the girls will be kicking yer door down n all!

Hahaaaaaa!

rpruen · Post by **rpruen** » Thu May 24, 2007 9:03 pm

clubman_dan wrote: does anyone have any part numbers for the gasket? i went to volvo and its about Ã‚Â£32! even the guy on the parts desk thought that was a bit steep.
and i tried a couple of motor factors who told me that its dealer only.
there must be a cheaper alternative!
not looking forward to doing this! looks pretty tight for clearance back there..
cheers
Dan

Unfortunatly there doesn't seem to be an alternative, as the Renault gaskets don't fit. The ports are not quite the same. There are cheaper gaskets for some of the early N/A engines, but they also don't fit on yours.

Also the job is a total PITA as you need to remove the turbo to get the manifold clear of the studs. There is also a silly little braket (not always fitted) that holds the manifold to the block, if you have that then you need to crawl up the back of the engine to undo it, the exhaust manifold end has a stud. To do it you may need to remove the starter motor for access

Hopefully you don't have the bracket, if you do it's near the turbo to manifold flange, under the exhaust manifold. It is a pressed steel bracket that goes down to the engine block.

I wish you luck, and hope you don't have the bracket.

Richard

clubman_dan · Post by **clubman_dan** » Fri May 25, 2007 10:41 am

dropped back in to volvo again this morning to order the gasket.
The guy on the parts desk did a bit of searching on the computer and found that up to a certain chassis number the gasket is called a heat shield and costs about 32 quid. after that its called a gasket and costs much less.
funny thing is they have identical part numbers! so he has ordered me a gasket (rather than a heat shield!) hopefully its ok.
i will check for the metal bracket, sounds like i don't want it to be there, so fingers crossed it isn't!
cheers
Dan

rpruen · Post by **rpruen** » Fri May 25, 2007 11:08 am

clubman_dan wrote:dropped back in to volvo again this morning to order the gasket.
The guy on the parts desk did a bit of searching on the computer and found that up to a certain chassis number the gasket is called a heat shield and costs about 32 quid. after that its called a gasket and costs much less.
funny thing is they have identical part numbers! so he has ordered me a gasket (rather than a heat shield!) hopefully its ok.
i will check for the metal bracket, sounds like i don't want it to be there, so fingers crossed it isn't!
cheers
Dan

Hmmm....

I think the heat shield is the part that joins the two sections of manifold together. That is a metal heat shield with a gasket either side, they are semi-reusable. If the gasket has gone, then the gasket you have found above can be fitted (you need two, part number 3344314) one each side of the heat shield. Remove the old gaskets and rivets that hold them to the metal part before fitting a gasket either side.

The gasket I was talking about is the intake and exhaust manifold gasket part number 3451590

Hope that helps

Richard

clubman_dan · Post by **clubman_dan** » Fri May 25, 2007 11:42 am

i have ordered the gasket that sits between the plenum and inlet manifold. and the actual manifold gasket, the one i was talking about above is the manifold gasket.
it arrives tommorrow, hopefully its all ok!