Intercooler

[mrlong]

I just bought a 1998 TDi with 165,000 KM (100,000 Miles) on it and took it to the dealer for a going over. There was front end damage - the grill was broken out, frame around rad was broken, a stabilizer connector broken, and they said that the intercooler had a crack in it. I've checked the mileage and I'm only getting 38 mpg (US). Heard I should be getting 50. Would the intercooler cause this? Everything else checked out OK.

[Smileybug]

Is the intake clean? That's huge with MPGs. I don't think the intercooler being cracked is going to bring your mileage down that much. Might 1 or 2mpg but not 12mpg worth. 38mpg isn't terrible. Is your car a manual or auto? What type of driving do you do (city, highway, mix)? There are a lot of factors that go into MPGs.

[mrlong]

Originally Posted by Smileybug

Is the intake clean? That's huge with MPGs. I don't think the intercooler being cracked is going to bring your mileage down that much. Might 1 or 2mpg but not 12mpg worth. 38mpg isn't terrible. Is your car a manual or auto? What type of driving do you do (city, highway, mix)? There are a lot of factors that go into MPGs.

They didn't seem to think there was carbon build up when they checked the car over. I just bought it so I've been trying it out a lot. Maybe my speed had something to do with it. They did think that the intercooler crack would affect the power a bit, and I think it's a bit sluggish when you first shift gears. Mine's a 5 speed manual. 38 is a lot better than my truck which gets 15, but I'd sure like to get it up to 50.

[Blugg]

Originally Posted by mrlong

Maybe my speed had something to do with it. 38 is a lot better than my truck which gets 15, but I'd sure like to get it up to 50.

Then slow down

My TDi gives me a return of 30-40 mpg when i'm heavy footed. If i'm driving 50-60mph i get a decent MPG. If your driving it hard everywhere, constantly using the turbo. Then say goodbye to any decent MPG figures

[h_2_o]

a cracked intercooler will cause more of a loss of power than loss of gas mileage. the intake manifold if it is clogged will be more of a power loss as well, but can cause some mpg loss. I can guarantee you that they did not check for carbon buildup on the intake manifold and being a '98 i'm sure it has some because that is pre clean diesel, i guess i'm saying they outright lied to you there. you said 5 speed so that should help out with the mpg compared to an auto. I would guess it would come down to your driving habits.


OK now i'm actually going to possibly contradict myself in the same post, if there is a crack in the intercooler causing a leak then the turbo would not get the same boost as it is asking for from the electronics forcing the engine to work harder to accomplish the same task. I would personally try an epoxy or possibly jb weld on it if it is a small hairline crack as i've seen guys do that on tdiclub.com to fix an intercooler.

if you get it figured out post back, and also is it throwing any codes when hooked to a vag-com?

[mrlong]

I'll try to keep my foot out of it for the next tank. Does anyone know how you'd check the carbon build up? It would be in their best interest not to lie about it if they wanted the labor to fix it. I don't have any engine codes - they fixed the glow plug that was causing one. I've ordered a new intercooler, but epoxy would have been a lot cheaper. Whoever had it had a front end run-in and the grill is broken, a stabilizer bar part is broken, the intercooler is cracked, the plastic frame around the radiator is broken, and the middle engine guard is gone. I'm getting an aluminum skid plate that covers everything for less money than the plastic ones. I live on a farm so I have a bit of gravel and need to protect the motor as much as I can. I want to look into some of those chips that promise more HP and MPG. Some say 40 more HP and 10% better mileage, but that's hard to believe. Anyone heard of these?

[Great98]

Do you have any service records? If the TB hasn't been done I think you'll want to get that done ASAP since the '98s came with a 60K mile TB change interval belt and tensioner set-up. Another thing to look at is the fuel filter. If that hasn't been changed recently you'll want to get that done and that can affect the MPG. An injector cleaning with a can of Lubro-Moly Diesel Purge will also help with a 100K mile '98. Good luck!

[mrlong]

It had 165,000 KM on it which is about 100,000 miles. The timing belt has been done twice, once by the first owner and once by the second. I'm waiting for him to mail me his service records. I put some Sea Foam in it yesterday, but don't know if it did anything. Good idea about the fuel filter. I had an experience with my farm tractor this spring to do with that. 300 HP tractor that had a hard time getting up hills and could hardly pull a seeder. Fuel filter change made all the difference in the world. Where is the fuel filter, do you know? I haven't gotten my service manual yet.

[h_2_o]

look at page 19 on this pdf and you can see what buildup really looks like, but this is a full instruction on how to take it apart and clean it

http://pics.tdiclub.com/data/517/Int...d_Cleaning.pdf

here is another link to cleaning it

INTAKE MANIFOLD CLEANING 101

and every so popular fire method of cleaning it, i would not dump it in water after cleaning as it might warp or crack it

YouTube - ‪Redneck TDI Intake Manifold Cleaning!‬‏

[Great98]

Fuel filter is in the engine compartment, passenger side down front next to the windshield washer fluid reservoir fill cap. It has rubber lines coming out of it, one from the tank, one goes to the injection pump and one is the return from the injectors. Good luck!

[mrlong]

Found the filter, but boy, is it expensive. There's a VIN number break and my filter is $74 and the ones after the break are $24. Have to find receipts to see if it's been changed recently.

Is there any way to tell if the intake is plugged with carbon without tearing it off? Engine check light the only way?

[h_2_o]

yes there is, however in doing the check you will knock off carbon and it will require a cleaning at that point. however the intake is more of a power loss than an mpg thing so i would see if your fuel filter needs changed and plug the hole in the intercooler first. Cleaning it is a good idea, but it is a nasty job, seriously you will throw away every piece of clothing that junk sticks to everything it is just nasty, that and it takes a while to actually do.

[mrlong]

So the garage must charge a fortune to do it?

[mrlong]

Second tank I got 42.6 mpg driving reasonable most of the time. Might get it to 45 or so driving reasonably all the time.

[mrlong]

And 47.14 today going on the highway at 65 mph without A/C on. I guess I'm in the picture after all. Getting a new Intercooler tomorrow so I'll test again after that. Power seems to be good to me though I've never driven a different one.

[TDI_bubble]

The system past the MAF needs to be sealed and pressure tested to ensure this. Any air leak means your engine is getting less air than what the MAF is sending to the ECU as intake air.
The VNT's are on boost quite a lot, so even a small leak makes a huge difference.

[mrlong]

Well,I seem to have a bit more power with the new intercooler. I imagine they did the pressure test at the garage. I'll have to check the mileage now.