1998 v70r - boost

[Bren]

So I'm just getting to know my volvo and everyone on this site has been extremely helpful so far - love this place.

I finally got around to replacing a couple of my clearly visible broken/leaking vacuum hoses and I'm starting to notice a difference in performance which is good...but I think I'm still leaving some performance on the table as the car still feels pretty sluggish and I have a feeling it has to do with boost leaks.

I'm experiencing little to no feeling of boost until about 5k RPM's and then I can feel the boost kick in...especially in higher gears. That seems so late and it takes a while for the car to get to there - and under normal driving 5k RPMs rarely happens...This sounds like a boost leak problem to me no?

I'm also hearing the turbo hiss from inside the car, pretty much across the whole rev range - is that normal? or is that my leak?

I'm working on getting a boost gauge so I can actually measure vac and boost levels but in the mean time, where are the trouble spots I should check? I'm going to try and block off my intake with something and fill it with some compressed air to see if I can track it down

[Scholz]

If you accelerate at half throttle and if your 98R is like my 98T5 you will feel the turbo at ~3050rpms. no mistaking it. Are you using some sort of OBD2 scan tool to look at real time information? I use Torque Pro for android. Being in the same boat as you without a reliable vacuum/boost guage, I was able to find all the little issues that were preventing my T5 from operating correctly. Fuel Trims both short and long, Timing Advance, Front O2 sensor readings, throttle position readings, and Engine Temp ended up being the ones I personally looked at to diagnose the issues. Which ended up being Throttle position Sensor, the Coolant Temp sensor and cruddy plugs/wires. Mind you I had no check engine lights. Luckily the more knowledgable people here were very very helpful. Looking at you Abscate!

[Seaway]

Intercooler hoses are a good place to start. The hose at the bottom of the intercooler on my car was a culprit. Inspect all of them for obvious holes and then tighten all the hose clamps. Also check the connection at the short hose at the top of the turbo.

Your TCV and associated vacuum lines is another good place to check. Depending on mileage - and to establish a baseline - you may simply want to replace them. You can get 5mm silicone vacuum tubing for cheap on Amazon and run this from the TCV to the turbo. Just do one at a time so you don't get anything hooked up incorrectly. Which brings me to the next check: Make sure all the hoses are connected from the TCV to the turbo correctly! Google "1998 volvo vacuum hose diagram" and follow the diagram with the colored hoses. My car once popped the hose from the CBV on the turbo back to the front of the intake manifold and it would not boost to the correct levels. Remove the air filter box and you will be able to see where all the lines go from the TCV to the turbo.

You can also check the vacuum tree under the plastic cover where the throttle cable runs. See if anything is unplugged there, and also check the hoses to the Idle Air Control Valve. The top hose can crack and the leak may not occur until the car is under boost. Take is off to inspect it.

Lastly, you can check the wastegate on the turbo and see if it is functioning correctly. There are a couple ways to do this - the safest being with a pressure gauge so you can set it correctly. But you can also tighten the nipple/connector on the rod one turn (shorten the rod - turn the connector thing towards the front of the car) and see how it impacts the turbo spooling. This will make the turbo begin to spool sooner. Too many turns and you risk damaging something, but if you are not feeling any boost until 5k rpms one turn should be a safe starting point.

Hopefully some smarter folks will chime in soon...

[ferocity02]

How hard would it be to pressurize the intake system to check for leaks? On my 335i it was pretty easy. I just used a PVC pipe cap with a fitting for the air compressor. I inserted this fitting into the intake hose and clamped it down. It pressurizing the whole intake system from the filter to the intake valves. I had to cap off the PCV hose so it wasn't pressurizing the engine block. I went up to 20 psi, probably not necessary on these Volvos.

Any reason not to do this on our cars?

[scot850]

Here are a few other issues to check out once you have thoroughly checked out all the vacuum and pressure pipes, as well as very carefully checking the turbo/intercooler rubber hoses, and finally check the intercooler itself for cracks. The bottom is more common.

Not sure about pressurising the system as you suggest but would be great if you can find a way that works and is safe. I for one would appreciate that!!

Once you are satisfied all is well, then continue with the other checks the guys have suggested.

Two of the main culprits that age affects are the TCV and the TBV. The TCV's fail with age as the valves become worn and slow to respond, or prevent the turbo spooling up. The Turbo Bypass Valve (or Compressor bypass valve) has a rubber diaphragm in it that can split with age. Good thing with your car is you should be able to replace it on your turbo without removing it. IPD and I think ARD do replacement kits.

If you want to see the pipe positions for the TCV, check out IPD's website as they have a down-loadable file with fitting instructions for their up-rated TCV. If you decide to fit their TCV, do NOT turn the plastic leg on the 'front' of the unit in any more than 3-4 turns. It may feel loose, but turning it in any further can allow it to jam on the internal valve (don't ask how I know!!).

Replacing the pipes to the TCV can be a major pain, particularly the one under the turbo. Patience and angled narrow nosed pliers are what worked for me along with a bendy mirror.

Finally, also check your fuel pressure. Needs to be at lease 43psi (3 bar).

Neil.