After reading and thinking about it. I was thinking about taking the preheater hose off. The dopey thing keeps splitting right at the exhaust manifold anyway.

I figure I will just let the car take a bit longer when warming up. I also thought that I will never fry my AMM if the Heater box T stat craps out (common problem) with this disconnected.

Either close it off entirely or run the hose to the passenger side. there is a covered hole by the Headlight that looks like a good candidate for additional fresh air.

Doe sthis make any sense to do?
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'75 Jeep CJ5 345Hp ChevyPwr and two motorcycles: it wasn't Volvos safety , it was Longevity that sold me

Thanks everybody. There are more of you than I thought that did this.

In New York they do Emissions (ridiculous scam) All I have to do is make sure the engine is hot before I get there...so long as it passes on the machine Everyones happy.
That damn machine puts more abuse to my car in 5 minutes then I do in two years. Braking hard, accellerating hard,and the exhaust getting cherry red because the car is working hard on the Rollers without the speed to cool the pipes.
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'75 Jeep CJ5 345Hp ChevyPwr and two motorcycles: it wasn't Volvos safety , it was Longevity that sold me

At the CT emissions stations, at least during warm weather they put big fan(s) in front of the cars when they were on the dynos, to get airflow thru the rads. Of course, now that we're moving to non-state-run facilities, that will probably change.

Interseting. Ct is moving away from State run facilities. New Jersey just went to all state run facilities..4 hour lines I was told and New York is private but they are on the fence. They were talking about the State run emmision stations. I guess I have nothing to do all day then get my Safety inspection at one place and my Emmissions somewhere else.
Silly
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'75 Jeep CJ5 345Hp ChevyPwr and two motorcycles: it wasn't Volvos safety , it was Longevity that sold me

The indy shop who worked on my first Brick removed the hose, and I never noticed a difference. I pulled it off my '92 and '91 240's and removed the 'stove' on the manifold as well. Here in CT the emissions inspectors I've seen to date would barely be able to tell the engine was missing, much less a half-hidden hose.

Starting and warmup shouldn't differ with or without the hose - at least until the exhaust manifold is up to operating temp, which takes a few minutes in cold weather.

Removing the pre-heated air from a mass meter system will pose no problem. The hot wire sensor will compensate and still accurately measure incoming air and the fuel required. Volvo used heated air on the 740 Turbos and then dropped it, which is a fair decision considering that they then passed the marginally heated air through the intercooler. My 88 740 Turbo "lost" its preheat when I bought it, and so far hasn't missed it...
On the k-jet system the warm-up regulator is calibrated to the heated air, but a simple adjustment of the base air fuel ratio compensates fairly well. My 82 240 GLT has no preheat, and draws air through an enlarged snorkel behind the grill. It has a momentary lean period during warm-up, but cold starts and runs hot just fine up here in Canada.
In the far north preheated air is a good idea, if only to maintain fuel economy, and for those that care, emission standards.

quote: "In the far north preheated air is a good idea, if only to maintain fuel economy, and for those that care, emission standards"

Just curious, does anyone know why most modern FI cars use preheaded intake air? Is it just for the emissions during warmup? How would cold air intake influence fuel economy and emissions once the engine is warmed up? I always thought cold=dense=more performance.

I also own a 94 Chev Camaro with the LT-1 engine. It does not use any preheat for the air, but it does have in intake air temperature sensor, and has a water heated throttle body to prevent ice formation. Lots of modern engines no longer use air preheat. I imagine some continue to do so - much depends on the engine management strategies employed by the various manufacturers.

This thread needs a dissenting opinion so here it is. I got two replacement airbox t'stats from FCP Groton ($7 each I think), and checked them out by putting the whole airbox unit in the freezer, then out in the sun. It was kinda cool to see the tiny 'stat push that flapper shut against that strong spring! I put them back in the cars (81 and 83) and put one of those little indoor/outdoor electric LCD thermometers in the airbox behind the filter, through the small rubber bung in the top, and the readout/display on the dash. Both cars would quickly heat up to about 60F on a chilly morning and stay there. So the thing works. When the temp did go above 60, it was because of the outside air temp rising.

If the sheet metal shroud on the downpipes rattles, tighten its bolt.

If you don't have a working stat (ie: failed to the hot position), and you just disconnect the hose, you are still drawing air from inside the engine compartment, which will be plenty warmer than ambient temp. This can be cured by running the other end of the preheat hose to a cool air location, modifying the airbox so it draws only from the front snorkel...(or by putting in a working stat).

Before I got the new stats, I had the preheat hose disconnected and the smog tech spotted that and reconnected it and noted it in his report. So at least in CA, they check.
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Bob (81-244GL B21F, 83-244DL B23F)

I checked my hot air valve in the airfilter box shortly after getting my car a year ago, and it was stuck open. I removed the valve and removed the hot airhose. I also removed the heat collector bolted to the manifold, it was always rattling. I'm pretty sure the heaterhose is just ment to reduce some emissions during warmup and doesn't effect drivability at all. In fact, if anything, you should get slightly better performance (don't know if it's measurable) because cold air is denser therefore more o2 more fuel bigger bang.

I've disconnected mine and the car runs fine here in western Oregon. You should check to see if the thermostat has the flapper valve stuck in the position which directs air from the heater to the air filter. Mine was and this meant that I was only getting air through the heater hose, not the front snorkel. I took the air filter box out, removed the flapper valve mechanism and blocked off the heated air input opening. I considered running the metal heater hose out to the front and having two air sources for the engine. It might be a good idea, I'm not sure though.

It all depends on where you live: average winter temperature, local emissions testing, etc..

I bought my brick at 59k, and removed the pre-heater hose as my first "maintenance" job. I'm in the Southeastern USA, with relatively mild winters. The temp drops below freezing overnight, but warms back up by 7-8am. Also, my area does not have annual emissions tests for passenger cars, so I don't have to worry as much about exhaust fumes during initial warmup.

[[ southern fried volvo '91 240 124k mi ]]

I have a 1980 245, k-jetronic, N/A, second owner for almost ten years. I removed the hose somewhere in the first year that I had the car and removed most of the wall of the air cleaner box so that most of the filter is exposed. The car runs great and always has. I am in Florida so I don't have sub-zero start-up temperatures to deal with (or emissions inspection) but it is fine down to 30 degrees F.

Go for it! Mine has been disconnected for 2 years with no problem. Slightly longer warm-up in cold weather, otherwise you will never know the difference!!



Jim 90 244DL 211K

I have a 1992, 245. No turbo. Auto transmission. 103,xxx miles.
I removed my pre-heat hose this summer and have just left the hole in the airbox open.

The car seems to run the same. A few weeks back it idled rough but I cleaned the throttle body and checked the flame trap and it now seems to idle fine again.

I have removed hoses from an 83 carb model and a 93 injection. In my experience it doesn't make the slightest difference to warm up or running, just something less to rattle.
I have always found the thermostatic flap unreliable, tending to stick partly open. If it does that, it lets hot air in all the time. Once pulling hard up a long hill I smelt burning, and it was hot air burning the air cleaner element.
I pulled out all the mechanism inside the black box and blanked off the inlet.

I have a header and cold air intake, so no pre-heat or restrictive air box.
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92 244 lowered, Bilsteins, IPD sways, Unitek cam/header, TSW Revo 18x8's - 94 965 Niiice MONEY PIT! - 76 Datsun 280Z lowered, modified head, cam, headers, intake