Very high temps with factory HAI

[ShadeTreeMech]

My Volvo has a fairly aggressive hot air intake that I'm starting to wonder about. It generally will automatically adjust the intake air temp to around 100* to 120* F regardless of outside temps by adjusting a damper between the outside air snorkel and the stove pipe coming from the shield around the exhaust manifold. It seemed to stay fairly constant, so I never worried about it.

But yesterday was the exception. I noticed a couple days ago my thermostat is apparently stuck open because it was not getting up to temperature. So yesterday I blocked 90% of the radiator with cardboard before going on a 500 mile round trip. The outside temps were from 18*F to 27*F all day, so we were using the heater constantly. The engine did not get over 140* until it sat idling at a gas station for about 10 minutes, then it was at 186*. It dropped down to 150* or so fairly easily, which is where it stayed for the most part. The weird thing was, despite the cold, the intake air temp (measured via SGII) nearly matched the coolant temp for the whole trip. I also did not get very good economy during the trip, getting around 24 mpg which may have been because we were going about 75mph the whole way there.

I know HAI are sometimes used to good effect to improve economy. I am also running 87 octane in a Volvo that specifies 91 octane, but it doesn't seem to run any different with 87 octane, and it doesn't knock. The economy tends to be slightly better on the 87 also. The old girl just got an oil change and new plugs, so that should be good.

I guess I have all these puzzle pieces and I'm not sure how they fit together. Anyone have any insights?

[user removed]

Inop stuck open thermostats will drive other systems crazy. Why not just replace the thermostat? Is it a nightmare to get to?

regards
Mech

[Superfuelgero]

Too much grill block. Temp fine while using heater, spikes if idling or heater is turned off. I had the same recently. Generally takes 40-50 miles for it to spike up high enough to trigger the fan.

Fix the thermostat.

the Volvo is a mass air car. Mass air cars adjust the density of the hotter air automatically negating the WAI effect (sometimes worse).

On volvos, if that preheat valve fails, it will cook the MAF. I've seen this on my old 87 240, and 98 s70. It does work well at startup though, and below freezing, but isn't perfect.

On the 99 V70 I helped with (fathers) it liked cooler air, and actually a slight bit off ram (has to do with the throttle by wire and MAF).

[ksa8907]

My car uses a map and temp sensor and I've had it capped out at 200 degrees. It got slightly better mpg at light throttle cruising but if I prodded it at all mpg's dropped off faster than normal.

I've decided around 150 is pretty ideal.

[ShadeTreeMech]

I'm planning on changing the thermostat soon (it's easy to get to thank goodness!) but the air preheater has a broken vacuum line on it, and I can't figure out where it is supposed to be connected. This Volvo is a great car, but the Swedish do like doing things a bit different. One of the hardest things to deal with is finding decent prices on parts, which usually means going to eBay for pretty much all of it. I had my alternator go out, and the replacement was $300+ because I was too impatient to wait for a cheaper fix.

xntrx, you have any idea where the vacuum line for the preheater valve is supposed to go? I can't find a loose vacuum line anywhere, and the routing diagram is worthless to tell me. And why does the Volvo require a special antifreeze? Have you noticed there is a gap between the top washer on the strut mount and the actual strut mount? I replaced a strut mount, but the cross nut seemed to prevent tightening the nut down all the way, so I took it out. Couldn't see why the thing was supposed to be made to rattle around.

[Superfuelgero]

Its been awhile since I've had that car in front of me. I got out of the volvo scene about 5 years ago after being very heavy into it. The best thing I can tell you is to join a volvo specific forum such as sweedespeed. I made good contacts for new parts (cheaper than ebay) on the forums. Also another thing you can do to learn is start going to the self service junkyards. Volvos unfortunately are disposed of too early due to expensive mechanics and parts. At the self service yards though, it doesn't matter if its a hyundai or a volvo, same price. It is good practice since if it breaks, you can walk away.

[ShadeTreeMech]

I just got the car less than a year ago, and it has been a joy for the most part. But it is certainly a bit different to work on. I think I'm lucky to have the non turbo engine, as it seems a lot less complicated under the hood compared to the turbo varieties I've seen video of.

I did finally figure out where the vacuum line went to. The vacuum diagram kinda said where the line belonged, just had to read between the lines a lot.

Any Volvo specific hints as to how to get her to cough up better economy? You'd think a car like this should be capable of better than 25 mpg.

[Superfuelgero]

There's no magic bullet for volvo's, just the normal mods: Scangauge (its also easy to replace the cluster with the factory trip computer, plug and play), and making sure everything is functioning properly. This should net 32-34 on the open road with a n/a v70. Beyond this, you'll have to get into aero mods. Volvos are "bricks", anything you do (grill blocks, under trays, wheel covers, etc.) will net an appreciable difference.

[ShadeTreeMech]

Originally Posted by xntrx

There's no magic bullet for volvo's, (its also easy to replace the cluster with the factory trip computer, plug and play),

So the trip computer is in the cluster? That would be very handy, the scanguage is nice but it is clumsy to find a place for it where it isn't in the way or getting baked by the sun.

32 MPG on the highway would be outstanding. Since I have steelies, I'm going to try and hunt down some aero wheel covers, especially since I have one missing anyways.

I don't get why there is all the wiring available for the fog lights, but it was considered an option. I don't have them, but they are quite reasonable to purchase online.

I'm toying with the idea of modifying my bumper to block air and be more aero using some fiberglass etc. Guess I'll see how it goes, won't be able to mess with that til summer I'm sure.

Oh and I figured out where that vacuum line went and replaced it. Guess I'll see how it goes.

[brucepick]

Yes, the Volvo air intake thermostats die, and need replacement. Not too difficult. It's a wax-based thermostat; you can look that up in wikipedia for an explanation.

For an on line parts source for Volvos, try fcpgroton.com. Pay attention to what brand you get and where it's made. I also second the motion to use junk yards. BTDT with excellent results.

Volvo alternators (the 240 ones at least) have an easily replaceable brush and diode assembly. Comes out with a screwdriver with the alt still in the car! Costs about $35 from fcpgroton and usually gets your alternator working again. Sorry I'm a bit late with that news! Consider it a "wear" part, it just takes something like 100-200K miles for it to wear out.

We drove nothing but Volvo 240s (rear drive) for about 13 years and my stepdaughter still has one. I've done lots of work on those. Yours is newer though, front drive.