Amazon: Air Leak and Hoses

[edworcs]

Hi,

I'm pretty sure the rough running I experience is due to an air leak.

I've used up a good bit of WD40 spraying around the carb and manifold but couldn't detect any change in engine note.

It got me to thinking about the different hoses that are attached to the engine … I've attached a photo with numbered sections (sorry about the quality, but a mobile phone in the dark isn't the perfect tool).

This is a B20B engine with twin SU carbs. I have a hose connected between the big blue air filter (no. 1 in my photo) and the rocker cover oil filler cap (no. 4 in my photo). There are no valves in this link, just plain rubber hose.

I have a hose connected between the brake servo (no. 6) and one of the two nipples(?) (no. 2) on the manifold. This appears to have a valve just before the connection to the manifold (separate photo attached).

The final hose appears to be a plain rubber hose between the crank case breather (no. 5 - metal filter present and clean) and the second of the nipples on the manifold (no. 3).

Questions are:

Is the a sensible arrangement for the hoses?

Have I got the valve in the right place? I have a hunch that the valve should be between the crank case breather and the manifold and not the brake servo and manifold.

Do I need any more valves in any of the hoses?

Green book and this forum seem to have conflicting advice / opinions, so this isn't as clear to me as it could be!

Thanks,

Ed

[123GT-AMAZON]

Originally Posted by edworcs

Hi,

I'm pretty sure the rough running I experience is due to an air leak.

I've used up a good bit of WD40 spraying around the carb and manifold but couldn't detect any change in engine note.

It got me to thinking about the different hoses that are attached to the engine … I've attached a photo with numbered sections (sorry about the quality, but a mobile phone in the dark isn't the perfect tool).

This is a B20B engine with twin SU carbs. I have a hose connected between the big blue air filter (no. 1 in my photo) and the rocker cover oil filler cap (no. 4 in my photo). There are no valves in this link, just plain rubber hose.

I have a hose connected between the brake servo (no. 6) and one of the two nipples(?) (no. 2) on the manifold. This appears to have a valve just before the connection to the manifold (separate photo attached).

The final hose appears to be a plain rubber hose between the crank case breather (no. 5 - metal filter present and clean) and the second of the nipples on the manifold (no. 3).

Questions are:

Is the a sensible arrangement for the hoses?

Have I got the valve in the right place? I have a hunch that the valve should be between the crank case breather and the manifold and not the brake servo and manifold.

Do I need any more valves in any of the hoses?

Green book and this forum seem to have conflicting advice / opinions, so this isn't as clear to me as it could be!

Thanks,

Ed

Hi Ya Ed

all looks ok from the image regarding the hose from the front filter going to the oil filler cap , now your hunch is right i would fit the firetrap valve in the middle ( 3 & 5 ) from the crankcase breather up to the centre breather nipple off the minifold you should only have that one firetrap fitted in the arrangement thats the rule i follow with the setup you have there when i do them , i hope thats helped try that and see how you get on

ps - is the metal gorse inside the oil filler cap clean aswell ?? and when is the rough running at its worse hot ? cold ? idling ? or is it just overall rough runining have you looked at the dizzy and carbs to make sure there all ok

kind regards
robert

[edworcs]

Thanks Robert. Much appreciated. I've been down the carbs and timing/ignition route and while I can't rule them out completely, an air leak now seems the best bet for poor running. I have very poor low end acceleration making pulling away from junctions somewhat hairy. Above 2000 revs and the car goes very nicely. The car runs well for the first couple of minutes from cold running on full choke. The problem is not consistent. I returned from a 10 mile trip earlier, stopped, turned the engine off for a minute or two, started again and all was well. I could go on and on:-) I'd like to investigate air leaks right now, even if it so that I can rule this out as a possibility. My symptoms seem very similar to a number of posts in these search results:

http://www.volvoforums.org.uk/search.php?searchid=3172372

I've taken your answer to mean that I should swap the (PCV ?) valve that currently goes in the hose between the servo and number two nipple on the manifold to the hose that runs between the firetrap / crank breather case and number one nipple on the manifold?

Derek offers some advice for a B18 engine in this post:

http://www.volvoforums.org.uk/showthread.php?t=151900&highlight=air+leak

but I'm struggling to match the diagram shown with the set up I have.

[Volvo Canadian]

I have no valves on mine, but can see why you could use one from the crankcase breather. If there are no cracks visible, something could be blocking the hose on the inside, like a flap of rubber, but I don't see how any of that fits your description of the problem. It looks like you have done some homework too. If the engine is starving at low rpm it sounds more like a carb/fuel problem to me. Since she runs well sometimes at least, it should be a relatively minor fix once you find the problem. That's my two-bits worth.

[Derek UK]

I can't get either of those links to open so can't instantly check what they say. Basically the B18 and B20 systems work the opposite way to each other, that's why it's difficult to combine the two as far as routing goes. Haynes does show how they work but the flow direction arrows are a bit hard to see.
I think I would have the one way valve for the servo vacuum close up to the servo rather than at the manifold end. Don't just reverse it without also reversing the valve in the pipe. Does your servo seem to working OK? The pipe from the crankcase side ear to the manifold is open but the fitting at the manifold end has to have a restrictor in if there is no pcv valve at the ear end. Best to check that. Without doing anything else perhaps just take the pipe off the side ear and block it off and then do a test drive. If your acceleration from slow speeds, as mentioned, improves, it's probably because the vacuum is better in the manifold. Your "leak" is the suck from the crankcase via the side ear.
As James aid, as long as you have a correctly functioning line to the servo the rest can be either open or sealed off, with no piping. Best if the engine is running well and not smoky, otherwise not so good environmentally.

[Alf ista]

Originally Posted by Derek UK

Basically the B18 and B20 systems work the opposite way to each other, that's why it's difficult to combine the two as far as routing goes. Haynes does show how they work but the flow direction arrows are a bit hard to see.

Ron Kwas has a diagram on his site; sw-em.com. Here is a link to the page.

http://sw-em.com/pcv_diagrams.htm

Excellent, as usual.
Hugh

[edworcs]

Thanks to all for the helpful replies.

Hugh, Ron's diagram was one of my causes for confusion. This shows the B20 setup as being air filter to crank case ear and not air filter to oil breather. I'm easily confused ...

I tried removing the hose between the crank case ear and the manifold. Thanks Derek for the suggestion. I blocked the manifold inlet with a bung while I did this. No noticeable difference. Good. One thing ruled out.

I went round the engine with carb cleaner and WD40 (again) paying special attention to the carb spindles. No change in engine note.

I thought I'd look at the servo hose next. Derek suggested that the one way valve might be better at the servo end of things. Well, the one way valve doesn't really live up to its name. It is sometimes a one way valve and sometimes a no way valve. I am consistently able to blow through the black end (picture included) and for it to be blocked. If I blow through the white end at an even(ish) pressure air flows and then stops. It sort of feels like James's flap in the hose idea. Any how, the behaviour isn't consistent.

I've never really understood the brake servo principle, but I would have thought that the servo should be "powered" by air from the manifold? In other words, the valve should allow air to flow from the manifold to the servo, but not from the servo to the manifold. Is this correct? In my case the valve looks like it would have blocked any air going out of the manifold to the servo, but would have allowed (sometimes) air to go from the servo to the manifold. This doesn't feel right.

I think a new one way valve might be a good idea. Are they filled with gold dust? £20+ for a plastic valve seems a little more than I was expecting :-)

Ed

[edworcs]

So, the article I've just read tells me that my idea was plain wrong:

http://auto.howstuffworks.com/auto-p...wer-brake1.htm

a one-way valve that only allows air to be sucked out of the vacuum booster. If the engine is turned off, or if a leak forms in a vacuum hose, the check valve makes sure that air does not enter the vacuum booster.

So, my setup was probably the correct way around. Air could flow (mostly) from the servo to the manifold, but not the other way around, which, according to the above is correct.

[swedishandgerman]

I have to say it, but I think you might be barking up the wrong tree mate. Your symptoms aren't typical of an air leak.

I would say you need to go right back to the start and check your timing. First things first, are you sure you've set your points completely right? In fact, have you put a new set of points in there? Check them and check them again! Even better, do you have a dwell angle meter?

Even though your symptoms aren't those of knackered points (misfiring, uneven running at low - mid engine speeds) you can't check timing properly until the points are proper.

Next, does your car have a vacuum advance or retard? If it doesn't have either - GREAT! If it does, then disconnect the pipe at the carb end and give it a suck. If there's resistance, good. If you continue sucking and sucking, there's your problem. If this is the case, get back to me and I can help you out

To me, your symptoms say your distributor is not advancing properly so next, take off the distributor cap, grab hold of the rotor arm and twist it. If there is no resistance and flops to and fro, there's your problem. If it has good resistance and it it springy, it's good. Now's the time to add a couple of drops onto the felt pad under the rotor arm and through the side oiler, if it has one, that is. Also you should thoroughly check your the metal nodes in the cap and the rotor arm. Any signs of deterioration, just change them - they're not expensive.

Do you have a strobe timing light? If you do you can get a better diagnosis of the advance. Take one reading at idle take another at 2,000rpm. It should go from circa 10 degs to =/<34 degs. If it stays at one setting or moves little, you're due for a distributor rebuild. Again, get back to me and I can help you out!

You're confident the spindles aren't leaking and you would notice this mostly when you are running just at part throttle openings (I really mean just) rather than closed (idle) or even partially open (IE: more than just open). This would give the same symptoms as a partial air leak through a broken pipe or broken manifold gasket. At idle, you can make adjustments to compensate for a partial air leak that then come to light as soon as you fractionally open the throttles. Once the throttles are more than fractionally open, enough air is getting in that a partial air leak will make sod all difference!

If you are absolutely sure that you have definitely balance each part of both carbs (mixture the same - that's very important - and airflow as well as both pistons lifting in harmony) then it should run smoothly at all throttle openings.

If I understand correctly from your description, you are saying that the problem is engine speed dependent rather than throttle opening dependent, right?

Right now and with reference to your worry about your pipes, I would leave the pipe from the manifold to the crank breahter unhooked and bunged, just leaving the servo attached. Also, to test your valve, I would suck it rather than blow through it

[arcturus]

sounds to me that you should be looking at your condenser also. A faulty one gives the symptoms of fuel starvation.