Hello.

On my 1993 Volvo 240 Sedan, I noticed that there was a broken pipe hanging off the exhaust manifold. I recently bought this car used and the previous owner is nice enough to buy me a new hose (since it was broken when he sold it to me) as long as I find out where it is meant to go to.

I desperately need to replace that pipe because the engine feels severely robbed of power, and I feel that this contributes to that because the exhaust system is losing all of its back pressure.

I will attach a picture, but I want to note that I took the broken part off, but it is the short pipe coming off of the exhaust manifold right next to the oil filter.



I also have one other question. When I was checking out the engine bay, my friend pointed out that on top of the air-cleaner box, it looks like there should be a hose or sensor or something in its place, but there is nothing. I will attach a picture of this as well, and just to be specific, he was referring to the small opening on top with the two bolts next to it.



Thank you for any assistance you can give me!

 

this broken pipe on the exhaust manifold... is it small, like 1" or smaller, or is it like 2-3" in diameter?

a small pipe likely would be EGR, and it points towards the back of the car, the EGR pipe snakes around the back of the block over to the intake side, goes to the EGR valve, then that valve connects it into the intake manifold. the EGR valve is actuated by a EGR vacuum thing, thats connected to a vacuum actuator on front side of the left suspension tower.

the large pipe pointing forwards is for the 'heat riser' pipe, looks like a piece of clothes dryer hose, and connects to the bottom of the airbox, where there's a flap thats opened by a thermostat spring only when its very cold outside. these flaps often stick open, and cause hot air off the exhaust manifold to be sucked into the engine, where it both cooks the MAF (mass air flow meter) and reduces engine efficiency. I recommend discretely wiring that flap shut with a bit of bailing wire. in smog inspection areas, you have to have the hose installed but noone checks the flap.

 

I looked around to try and find any places that were missing pieces that these could lead to, and I took pictures, so hopefully you can tell me if I'm right in thinking this.

Could this be where the exhaust manifold pipe leads to? Its an open port on the very bottom of the airbox (sorry, its tough to make out in the picture, so I highlighted the spot). Is this the spot where you meant the flap was supposed to be?

If so, is there anyway to get a working flap installed? Its getting cold where I live and I'm guessing it may help with cold starts.



Also, for the port on top of the airbox, could it lead here? It is behind the right strut tower (however, I mean right as if you had the hood open and you were looking at the engine bay) and next to the brake booster.



Thanks Again!

 

maybe if you post a link to your pictures...

 

p.s. the flap and heat riser doesn't help with cold starts either, as the exhaust manifold is cold. it might help with fuel economy or something if you're driving in deep sub-zero conditions, but we never noticed any problems with our 240 thats had that flap disabled since forever on ski trips to that frozen h*** known as Truckee and the rest of the Lake Tahoe area.

 

The large pipe coming off the exhaust manifold indeed is supposed to route to the lower intake on the air box. The flapper inside the air box has a thermostat switch that is supposed to open the flap to allow a certain amount of warm air from the exhaust to mix with cool air coming in the front of the air box. The purpose is to provide the air intake to the manifold to come in at a fixed temperature.

As Pierce said, this aids fuel economy more than cold starts. Many people disable or remove the flapper and close the lower intake in the air box. Usually what happens is that the thermostat fails in the air box and lets in lots of hot air from the exhaust manifold which quickly fries your air mass meter - a very expensive component. On my cars, I have removed the big fat hose entirely to eliminate this potential problem. I live in the Chicago area where sub-zero temperatures are expected every winter.

 

If I was to keep the hose removed, what would you suggest doing about the pipe hanging off the exhaust manifold? With that little pipe hanging off and going to nowhere, the exhaust system is losing all its back pressure.

 

the air riser thing we described doesn't connect to the exhaust itself, it connects to a heat riser plate thing thats bolted around the exhaust, its just taking hot air off the outside of the exhaust pipe.

can you post some pictures of what you are talking about? us guessing isn't helping here.

 

And Google exhaust back pressure while you're at it. Turbo cars need no back pressure and an n/a car like yours needs precious little. The exhaust manifold is sufficient. If you have a loss of power and you think it is exhaust related, then examine your catalytic converter. More likely, you're just underwhelmed by 114 screaming ponies dragging your 240 down the road.

 

yeah. what swift sez... anyways, if there was a 3" pipe coming off the exhaust open to the air, your car would sound like a straight pipe harley on steroids.