How long should a turbo vane actuator hold vacuum for?

casm · **Joined:** Sun Jan 29, 2006 5:05 pm **Posts:** 694

In the process of tracking down the last of the CRD's performance issues, I put the Mityvac onto the vacuum hose running to the turbo vane actuator. It would pump up to 26psi, but took a fair amount of rapid pumping below 10-12psi to retain pressure long enough to let it build up. Above that point, it would pump to 26psi, but would bleed off slowly at a rate of about 1psi per minute for the first 5-6 psi, then increasingly quickly after that.

So, my question: if the turbo vane actuator is in good shape, how long should it be able to hold vacuum for? There are no hose leaks and the seal at the Mityvac was good, with its internals presumed to be in good shape.

Note that driving around for a week with the vacuum solenoid bypassed didn't change anything. Neither did cleaning the MAP sensor. At this point, the only parts of the intake system that haven't been replaced are the turbo and the intercooler, so I'm beginning to wonder if there might not be something going on with them.

flash7210 · **Posted:** Thu Jun 18, 2020 3:50 pm

IDK how long it should hold vacuum.
But vacuum is constantly modulated by the vacuum control solenoids.
If the vacuum solenoid cant modulate vacuum enough to maintain sufficient boost a code should be set. Usually p0299.
Basically, high vacuum = high boost
Low vacuum = low boost

Whats the performance issue?
Are you getting a p0299 underboost code?
Are you able to monitor boost levels?

layback40 · **Posted:** Thu Jun 18, 2020 8:17 pm

IIRC its just a simple diaphragm device similar to an EGR or wastegate control.
The vane control runs on vacuum & so applying pressure risks damaging the diaphragm in it. Try applying vacuum to it. It should hold it indefinitely as its a closed system.
Have you tried moving the arm it actuates to make sure the vane control is not jammed?

casm · **Joined:** Sun Jan 29, 2006 5:05 pm **Posts:** 694

flash7210 wrote:

Whats the performance issue?
Are you getting a p0299 underboost code?
Are you able to monitor boost levels?

Same as I've been having for months: significant turbo lag off the line, massive soot when it's happening, poor fuel economy, poor performance. No codes are being thrown (or stored), and Torque is reading boost pressures as high as 21psi.

Unfortunately, it's an intermittent issue so likely will be difficult to track down. What I can say is that it's more pronounced when the Jeep is fully warmed-up than when it's cold.

Have confirmed no intake or vacuum leaks to the best of my ability. MAP sensor is clean and functional per Torque. Turbo vanes were cleaned late last year / earlier this year. Shouldn't have air in fuel as there's a Carter pump in the tank. No apparent fuel leaks. Fuel filter head was replaced last year shortly after the Carter pump went in as its primer diaphragm was shot and leaking. All hoses in the intake path are silicone; ditto the vacuum lines feeding the turbo modulator, etc. Air filter checked out clean.

layback40 wrote:

IIRC its just a simple diaphragm device similar to an EGR or wastegate control.
The vane control runs on vacuum & so applying pressure risks damaging the diaphragm in it. Try applying vacuum to it. It should hold it indefinitely as its a closed system.

Sorry, wasn't very clear on this in the original post. The device I'm using to test with (a Mityvac) is a vacuum pump, so no pressure is being applied to the diaphragm.

Quote:

Have you tried moving the arm it actuates to make sure the vane control is not jammed?

Yep, and it seems to be working, which is why I'm wondering if the actuator itself isn't the problem.

Right now I'm about two weekends away from being able to look into it in any depth again, but would love to hear any ideas. It's really confounding me as to where the problem may be, and since both the turbo and intercooler (high-dollar items if ever there were any) are the two things in the intake path that remain stock, I'd like to avoid throwing parts & money at them without good reason.

WWDiesel · **Posted:** Fri Jun 19, 2020 9:29 am

Have you replaced the little plastic tubing that runs from the turbo modulator valve over to the turbo actuator?
When I replaced mine with some larger good quality silicone tubing, turbo response improved greatly.

Kind of a "thinking outside of the box" idea,
put a "Tee" in the vacuum line that runs from the turbo modulator valve to the turbo actuator
run a long piece of vacuum tubing from "Tee" into vehicle and connect a good vacuum gauge
this way you can monitor exactly what the modulator valve/ECM is telling the turbo to do and when.

maybe the modulator is bad?
or, do you have full vacuum supply at the modulator valve?
either of the above two could cause what you are describing...

casm · **Joined:** Sun Jan 29, 2006 5:05 pm **Posts:** 694

WWDiesel wrote:

Have you replaced the little plastic tubing that runs from the turbo modulator valve over to the turbo actuator?
When I replaced mine with some larger good quality silicone tubing, turbo response improved greatly.

Yep, that one is long gone. The only factory vacuum line still remaining between the brake booster and the turbo vane actuator is the one going to the HVAC controls; everything else is silicone. I do need to get in there and replace that one.

Quote:

Kind of a "thinking outside of the box" idea,
put a "Tee" in the vacuum line that runs from the turbo modulator valve to the turbo actuator
run a long piece of vacuum tubing from "Tee" into vehicle and connect a good vacuum gauge
this way you can monitor exactly what the modulator valve/ECM is telling the turbo to do and when.

Which is not a bad idea :mrgreen:

It's not like I've never seen a sensor be out of touch with reality, so it may be possible that Torque's being fed bogus numbers from the ECU.

Quote:

maybe the modulator is bad?
or, do you have full vacuum supply at the modulator valve?
either of the above two could cause what you are describing...

At this time, I believe the modulator to be OK. It was replaced last year, along with the vacuum solenoid.

As for full vacuum supply at the modulator valve, that should be the case, at least as best I can tell.

WWDiesel · **Posted:** Fri Jun 19, 2020 10:42 am

casm wrote:

As for full vacuum supply at the modulator valve, that should be the case, at least as best I can tell.

Put a gauge on it, it should have full vacuum on supply side of modulator valve even at idle since it is supplied by a vacuum pump.
If vacuum is low due to a poor performing vacuum pump or a leak somewhere, it should be affecting the brake booster and HVAC controls.
A mechanical gauge will tell all....

casm · **Joined:** Sun Jan 29, 2006 5:05 pm **Posts:** 694

WWDiesel wrote:

Put a gauge on it, it should have full vacuum on supply side of modulator valve even at idle since it is supplied by a vacuum pump.

Good point, hadn't thought it completely through. Will give that a shot.

Quote:

If vacuum is low due to a poor performing vacuum pump or a leak somewhere, it should be affecting the brake booster and HVAC controls.

Brakes feel fine and the HVAC controls work as expected - but that doesn't mean that they couldn't be low-but-functional-enough. I do want to replace the main vacuum hose from the vacuum pump to the brake booster with silicone just to have everything in the vacuum circuit(s) replaced, but that's incidental.

Quote:

A mechanical gauge will tell all....

Might have a little time on Sunday - will try to look at it then.

Oldranger · **Joined:** Tue Feb 11, 2020 8:41 pm **Posts:** 29

I’ve been chasing a under boost problem for awhile now. You should read around 26 on vacuum on the line going to the booster. I’ve also tested mine and get 14 on the line going to the turbo actuator, all numbers at idle. I think my actuator is out of adjustment is my problem.

casm · **Joined:** Sun Jan 29, 2006 5:05 pm **Posts:** 694

Oldranger wrote:

I’ve been chasing a under boost problem for awhile now. You should read around 26 on vacuum on the line going to the booster. I’ve also tested mine and get 14 on the line going to the turbo actuator, all numbers at idle. I think my actuator is out of adjustment is my problem.

That's a possibility. What has me confused is that the problem only starts to surface as the KJ warms up, and gets gradually worse (to a point) once the engine is fully up to temperature.

I'm suspecting a damaged diaphragm in the actuator, or some other issue internal to it. Need to get some vacuum readings and give the turbo / actuator another eyeball, but probably can't do that until the weekend after this coming one.

flash7210 · **Posted:** Wed Jun 24, 2020 7:09 pm

casm wrote:

That's a possibility. What has me confused is that the problem only starts to surface as the KJ warms up, and gets gradually worse (to a point) once the engine is fully up to temperature.

What you describe sounds like my typical hot afternoon with the AC on.
As in, HIGH intake air temperature.

Could also be high fuel temperature but I've only noticed that when below 1/4 tank.

casm · **Joined:** Sun Jan 29, 2006 5:05 pm **Posts:** 694

flash7210 wrote:

What you describe sounds like my typical hot afternoon with the AC on.
As in, HIGH intake air temperature.

Could also be high fuel temperature but I've only noticed that when below 1/4 tank.

Fair points. It takes a while for the KJ to reach this point, and I'm doing about 100 miles of driving (almost entirely in town; perhaps 20% is on 50-60mph rural roads) before it gets really bad.

In other news, I may have finally found a culprit for the suspected turbo vacuum actuator issue. It feels as though the brake booster may be getting to the end of its life at 162,500 miles. Had to do a couple of hard stops in the past two days, and found that power assistance is significantly lower than it has been. Going to break out the vacuum gauge tomorrow and confirm, but that could very well be a massive leak in the system. It's also possible that the check valve on the booster is giving out, but that was replaced a little over two years ago so is less suspect at this time.

WWDiesel, if memory serves, you replaced the vacuum line feeding the HVAC controls with silicone tubing. Any tips on how to get at everything? I remember that tee on the passenger side of the firewall as being fiddly as hell, but can't remember what I found on the back-of-the-glovebox side.

casm · **Joined:** Sun Jan 29, 2006 5:05 pm **Posts:** 694

Took a bit longer to make progress on this than expected, but made a couple of discoveries in the process.

Firstly, the part number (5072522AA; aka 05072522AA) for the brake booster check valve used on the CRDs is specific to the CRD. Good luck finding a new one; they're completely discontinued. The major auto parts stores think that the check valves were the same on both diesel and gas models; they weren't. While one of their works-on-all-KJs check valves will physically fit on the CRD, it lacks the vacuum port used to send vacuum to the HVAC controls and turbo actuator.

However, it appears as though Mopar part number 4796355 (aka 04796355) may work as a replacement - just keep the cap on the green vacuum port in place. Note that I am not at this time definitively suggesting that this is the long-term replacement part; it's only been installed in the KJ for a couple of hours and maybe 30 miles.

Soot is at the lowest level I've seen it in months, responsiveness is definitely improved (very noticeably so off the line with the A/C on), and fuel economy remains to be measured. The brakes are better, but I still suspect that the booster may be getting weak. Will investigate that once I've had time to see how replacing just the check valve goes.

WWDiesel · **Posted:** Fri Jul 10, 2020 3:39 pm

The vacuum on the turbo actuator is controlled by the boost modulator valve. Not sure if it dumps the vacuum totally when you switch the key off.
Do know the little vacuum canister reservoir is supposed to hold vacuum in storage for the modulator valve.

As to a check valve, one of these should work since the OEM check valve has been discontinued.
Part Number: 05016730AA [Supersession(s): 5016730AA]
Fits 2001-2004 Dodge Durango, Dakota, Viper, Quad cab. Club cab.

There are quite a few two fitting brake booster check valves around, just have to find one with the right size fittings.
Some early Fords like T Birds and Mustangs also used two fitting check valves.

And, you could also just cut and add a "Tee" brass fittings in the main vacuum line going to the brake booster and connect the vacuum for the turbo and the HVAC which already has a small check valve in it's line.
You could also use a metal one similar to this:
Look at Summit Racing, they got plenty of them listed. Just file off some of the threads and wrap in teflon tape.

This is another PN check valve that has two connections that might could be utilized. It fits Jeep Compass and Dodge Calibers
68045449AA

Plenty of these two check valves listed above available online.

casm · **Joined:** Sun Jan 29, 2006 5:05 pm **Posts:** 694

WWDiesel wrote:

The vacuum on the turbo actuator is controlled by the boost modulator valve. Not sure if it dumps the vacuum totally when you switch the key off.

Based on what I've seen from removing various vacuum lines after shutdown (sometimes immediately, sometimes overnight), it does hold some vacuum when the engine's off. There is likely some bleed-off, though.

Quote:

Do know the little vacuum canister reservoir is supposed to hold vacuum in storage for the modulator valve.

Yep. It's effectively an accumulator for the modulator.

Quote:

As to a check valve, one of these should work since the OEM check valve has been discontinued.
Part Number: 05016730AA [Supersession(s): 5016730AA]
Fits 2001-2004 Dodge Durango, Dakota, Viper, Quad cab. Club cab.

There are quite a few two fitting brake booster check valves around, just have to find one with the right size fittings.
Some early Fords like T Birds and Mustangs also used two fitting check valves.

And, you could also just cut and add a "Tee" brass fittings in the main vacuum line going to the brake booster and connect the vacuum for the turbo and the HVAC which already has a small check valve in it's line.
You could also use a metal one similar to this:
Look at Summit Racing, they got plenty of them listed. Just file off some of the threads and wrap in teflon tape.

This is another PN check valve that has two connections that might could be utilized. It fits Jeep Compass and Dodge Calibers
68045449AA

Plenty of these two check valves listed above available online.

Yep, those are all options I've been considering. Think I may have found another issue related to this, though, so will post about that in a different thread.

How long should a turbo vane actuator hold vacuum for?

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