98 v70 warm/cool air intake door stuck

[98v70dad]

I have poor gas mileage on my 98 v70 with 124500 miles. I have done most of the items in the stage 0 list because I thought they were a good idea. After doing some reading tonight I think I probably need to check for a stuck door.

My air filter box has two (actually one is missing) white vacuum lines with black rubber lines going into the aft side of it. I don't know if those have anything with the operation of the door or not. I haven't looked at if for awhile but it looks like they pneumatically actuate something.....All the posts I read tonight talk about a wax valve which actuates the door. If anyone can tell me what the white lines do I really need to know so I can order and replace the missing one.

I'd estimate my mpg at no more than 15 on 87 octane fuel. I'm in the process of keeping track and having an actual figure, but i know the car is gulping down fuel. I filled it yesterday and it was down 4 or 5 gallons today when I got to work and I had driven maybe 75 miles tops.

The cold air only intake mod sounded like a good idea but its an old thread and there seemed to be at least a little disagreement about if was a good thing to do in colder climates with a lot of moisture in the air. Atlanta isnt that cold but every year we get freezing temps and temps in the teens for weeks at a time. The thought of having my throttle freeze in the open position doesn't appeal to me. Has there been any more wisdom in this area since people started doing this mod? I either need to get this door working again OR modify it to cold intake air only as many have done here.

I know I'm due for new 02 sensors. They are already on my to do list. The only difference from the list suggestions is I used NGK plugs instead of OE. They had some positive support as acceptabl alternatives. I didn't notice any big drop in mpg when I put them in, although I wasn't driving the car at the time.

[scot850]

Can I assume that your V70 is a non-turbo car, as it has the warm up pipe running from the exhaust manifold to the intake. I wish the turbos had this so they would warm up more quickly in the winter.
I haven't got an N/A Volvo at present, but I know the flaps on some older Volvos where operated by a thermal 'spring' which can fail. It should close as the engine warms up and pull most of the air from the fresh-air side.

If there is a pick-n-pull nearby the air intakes are usually cheap to buy. Easy to pull and swap over. If it makes no difference take it back!

Neil.

[98v70dad]

Can I assume that your V70 is a non-turbo car, as it has the warm up pipe running from the exhaust manifold to the intake. I wish the turbos had this so they would warm up more quickly in the winter.
I haven't got an N/A Volvo at present, but I know the flaps on some older Volvos where operated by a thermal 'spring' which can fail. It should close as the engine warms up and pull most of the air from the fresh-air side.

If there is a pick-n-pull nearby the air intakes are usually cheap to buy. Easy to pull and swap over. If it makes no difference take it back!

Neil.

Correct. Its a non-turbo. Yes easy to replace the thermal spring by replacing it. That said, it appears that this was a poor design. Putting it back to good as new isn't what I want to achieve. I hopin g to improve it if thats possible. Thanks for your reply.

[dosbricks]

The 98s had a different actuator than the 850s. The top vacuum line at the rear of the air box top runs over to the engine. I assume the line that is missing is the lower line because it gets pulled loose by folks servicing the air filter. It runs down to the front lower inboard corner of the air box--just under the corner actually. That is the fitting to a vacuum diaphragm that operates the headed air flapper. It's controlled by that little thermostat inside the air box lid. Replace this line and see if it restores the function of the heated air flapper. You can check its function by removing the cold air snorkel to the air box with the engine running and fully warmed up. Look inside the air box cold air tube with a mirror and see what is the position of the flapper. If it isn't working (cold air closed), mod the box--because a new vacuum actuator is $$.

I did the cold air mod on both our cars, but did not see the kind of performance increase on the S70 that was very evident on the 850. My wagon regained about 25hp from this no cost mod. The S70 maybe a little bit.

Your poor gas mileage is probably due to the failing O2 sensors.

FWIW, I've tried the NGK plugs and the electrodes don't last. Also tried Bosch Platinum and they performed poorly long before their claimed service life was up. You can not beat the original Volvo 3 prong plugs on a 2.4 NA for performance and service life. This opinion is based on 32 combined years of owning our 2.4 NAs. Just saying.

[98v70dad]

The 98s had a different actuator than the 850s. The top vacuum line at the rear of the air box top runs over to the engine. I assume the line that is missing is the lower line because it gets pulled loose by folks servicing the air filter. It runs down to the front lower inboard corner of the air box--just under the corner actually. That is the fitting to a vacuum diaphragm that operates the headed air flapper. It's controlled by that little thermostat inside the air box lid. Replace this line and see if it restores the function of the heated air flapper. You can check its function by removing the cold air snorkel to the air box with the engine running and fully warmed up. Look inside the air box cold air tube with a mirror and see what is the position of the flapper. If it isn't working (cold air closed), mod the box--because a new vacuum actuator is $$.

I did the cold air mod on both our cars, but did not see the kind of performance increase on the S70 that was very evident on the 850. My wagon regained about 25hp from this no cost mod. The S70 maybe a little bit.

Your poor gas mileage is probably due to the failing O2 sensors.

FWIW, I've tried the NKG plugs and the electrodes don't last. Also tried Bosch Platinum and they performed poorly long before their claimed service life was up. You can not beat the original Volvo 3 prong plugs on a 2.4 NA for performance and service life. This opinion is based on 32 combined years of owning our 2.4 NAs. Just saying.

I honestly can't remember what plugs I put in the car. One Saturday I'll have to take one out and see what it is. They may be volvo plugs, I just can't remember. I bought the wires rotor and cap from a guy who sells volvo oe parts. As for the vacuum lines I was at the dealer today and they are never able to tell me the part numbers for those vacuum lines or where they go. This is the second time they have tried to figure it out for me

[scot850]

A picture or 2 will help us to try and help figure out what goes where. Take one picture of the general area so we know where we are looking in the engine bay, and then some closer up so we can try to figure what pipes go where.

Neil.

[rspi]

O2 sensors.

[98v70dad]

The 98s had a different actuator than the 850s. The top vacuum line at the rear of the air box top runs over to the engine. I assume the line that is missing is the lower line because it gets pulled loose by folks servicing the air filter. It runs down to the front lower inboard corner of the air box--just under the corner actually. That is the fitting to a vacuum diaphragm that operates the headed air flapper. It's controlled by that little thermostat inside the air box lid. Replace this line and see if it restores the function of the heated air flapper. You can check its function by removing the cold air snorkel to the air box with the engine running and fully warmed up. Look inside the air box cold air tube with a mirror and see what is the position of the flapper. If it isn't working (cold air closed), mod the box--because a new vacuum actuator is $$.

I did the cold air mod on both our cars, but did not see the kind of performance increase on the S70 that was very evident on the 850. My wagon regained about 25hp from this no cost mod. The S70 maybe a little bit.

Your poor gas mileage is probably due to the failing O2 sensors.

FWIW, I've tried the NGK plugs and the electrodes don't last. Also tried Bosch Platinum and they performed poorly long before their claimed service life was up. You can not beat the original Volvo 3 prong plugs on a 2.4 NA for performance and service life. This opinion is based on 32 combined years of owning our 2.4 NAs. Just saying.

Thanks again dosbricks. I bought a piece of bulk vacuum tube and ran it from the lower attach point to the vacuum operated actuator on the inboard lower front side. While I was at it I applied a vacuum to see if the actuator works. It works but it doesn't close the warm air side off tightly. I don't know if its supposed to be that way or not. Do you know the answer to this?

Basically I got a partially opened valve door in both modes (open and closed) . That said, I applied the vacuum by sucking on the end of the hose which isn't a very strong vacuum.

[mika]

The 98s had a different actuator than the 850s.

97 850 has the same vacuum operated flapper as the 98. 96 and lower has the wax capsule thermostat.

The vacuum operated ones do not get "stuck" like the older ones. Chances are it is working well.

imperative this system is working in cold/winter states

to answer OP's last question:
-it often does not close "tightly" as we would expect. In my experience, any leakage is negligible. Think about how much air is being sucked in under acceleration. Any "air direction guide" will do its job.

I once tried to use foam tape and sealant to create a better seal on the flapper, and I did not notice any difference.

my NA had horrible gas mileage (15mpg) until I:
started using the correct grade oil (10/30), forget 15w40 or 20w50 even if 100+
lubricated my throttle cable spring (was so dry)
checked condition of E-brake pads: mine were seized on one side, loosened all. Ebrakes on autos create problems.
addressed CLOGGED PCV: pulled dipstick for time being. How can engine breathe if its sinuses are clogged?

want to replace throttle cable/lubricate cable asap

[98v70dad]

Mine was "stuck" because the previous owner had removed or lost the lower vacuum hose. I knew the vacuum line was missing but had no idea what impact it might have until recently. The valve closes maybe 80 percent. I can see daylight all around it. Maybe the airflow pushes it tightly closed.