1997 S70 'Red' Turbo Vacuum Line

Vuym · Post by **Vuym** » 18 Jan 2025, 09:47

coop wrote: 18 Jan 2025, 07:57 Check the line that goes to the fuel pressure regulator if the ones off the tcv look good.
It runs from one of the intake nipples to a hard line in the front of the engine under the intake tube that’s hard to see but that might have broken as well.

Do you mean this line?
https://ibb.co/6nFd25c

If it is, then yup that has also snapped off. I think RobertDIY said it brings in warm air to prevent cyrstals from forming in the tube or something. It's been added to my long list of 'to-do' work!!

coop · Post by **coop** » 18 Jan 2025, 09:56

Yea on the opposite side of the nipple that then has the small “j” hose that goes into the turbo control valve.

I think there’s like five lines in total that I needed to replace. Then a couple random pieces up by the radiator as well. 5mm silicone tubing took care of most of it.

Vuym · Post by **Vuym** » 18 Jan 2025, 10:03

coop wrote: 18 Jan 2025, 09:56 Yea on the opposite side of the nipple that then has the small “j” hose that goes into the turbo control valve.

I think there’s like five lines in total that I needed to replace. Then a couple random pieces up by the radiator as well. 5mm silicone tubing took care of most of it.

Nice one mate, that's very helpful. I should probably be marking the lines the way you did. Did you use 5mm for all the TCV lines? I've been using 5mm rubber hoses and they are snug but could probably feel tighter

Also, does that 'blue' line (TCV to Air Hose) allow the TCV to vent excess pressure or vacuum signals back into the air intake system? Could that perhaps be contributing to this compressor surge issue I'm having do you think?

coop · Post by **coop** » 18 Jan 2025, 10:33

I think there’s 3 different sized lines in total but the 5mm should work on most of them. The smallest lines that are like 3mm are usually hard and then have vacuum elbows that you could just replace with 5mm line or just replace the elbows.

It was easier for me to order the tubing online as most of the auto parts stores here don’t stock metric vacuum tube. The sae equivalent works but the silicone tubing I got from ipd is a lot easier to work with.

It’s probably a simple leak or cracked tube somewhere. You may want to also check the snorkel off the radiator and the turbo inlet pipe coming off the top of the radiator. The larger 3”? Silicone tube wears out and may be adding to the issue as well

Once you understand all the lines it’s not the complicated but it was confusing as hell for me to track them all down that’s why I ended up marking them all.

Vuym · Post by **Vuym** » 20 Jan 2025, 08:40

Strange.. I replaced the TCV and ALL connecting hoses and now I'm getting a P0243 Turbocharger Wastegate Solenoid A Malfunction code. It does feel like it's overboosting but purely subjective until I hook up a boost gauge. Could this fault lie in the electrical connection to the TCV? I've noticed no difference in function since going from an old TCV with 0 connected hoses to a new one with new vacuum hoses.

coop · Post by **coop** » 20 Jan 2025, 08:53

Do have the waste gate vac line going to the correct inlet on the tcv? They should be some paint marking them I think that one was yellow.

But I’d go over the turbo inlet pipe. Sounds like there might be something loose or cracked there

Vuym · Post by **Vuym** » 20 Jan 2025, 09:03

coop wrote: 20 Jan 2025, 08:53 Do have the waste gate vac line going to the correct inlet on the tcv? They should be some paint marking them I think that one was yellow.

But I’d go over the turbo inlet pipe. Sounds like there might be something loose or cracked there

I've routed things exactly as per this image: https://ibb.co/S5SNHhQ

I'm pretty sure the inlet pipe is fine, I had to take it off just to get to that red vacuum line.

I did buy a MityVac to try adjusting the wastegate arm but for some reason when I tried to push any pressure it would just stay at 0? Like it wouldn't even move even the tiniest bit so I just assumed I was doing something wrong (hose attached to wastegate yellow port to vacuum gun then set it to pressure). Surely I don't have a wastegate diaphragm that's damaged to that extent?

coop · Post by **coop** » 20 Jan 2025, 09:18

I think that code goes back to the tcv then the actual wastegate.

But double check the clamps on the inlet if you removed it.

You can always unplug the maf and see how the car runs without. Not that I’d suspect that to be the problem but if you have an air leak start there or the filter and go down to the turbo.

Vuym · Post by **Vuym** » 20 Jan 2025, 09:23

I'll give it a try and clean the MAF too - does that code mean there could be an air leak then? I thought it could mean that the car wasn't recognising the TCV

Some old posts I've seen reference this whole 'ECU re-learning process' whenever you change the TCV where the car has to be driven a few hundred miles to 'adapt' to the new TCV? Dunno if that could be related

Thanks again for the advice

Post by **abscate** » 20 Jan 2025, 09:41

The red line is a pressure line which takes pressure from the turbo to apply pressure to the watergate with the yellow hose. Pressure on the waste gate holds it closed and allows boost to build. The blue hose dumps any unused boost pressure back into the snorkel just upstream of the turbo

The TCV valve decides how much boost to send to either the waste gate or dump it back into the blue hose.

None of the hoses see vacuum. They need clamps to stop from popping off