L400 wastegate valve

[minicarz]

I have been having trouble with my L400, with what I believe is the wastegate valve. It problem is, under load(going up hill or harder acceleration) there would be a sudden load hiss coming from what sounded like the defrost vents , but of course it was not from there , but in the engine compartment. When this happens the power from the engine is greatly reduced. This occurrence now seems to happen all the time even under casual acceleration. As soon as go pedal is eased off it stops.

Now my questions are: (1) Is this the wastegate valve dumping turbo pressure? and if so, the valve is obviously defective as this should only happen under top end limits of the turbo, and not on casual acceleration on a flat road from a stop. I took it out , cleaned it up and it acts with the same disrespect.
(2) Where can I get one ?
(3) Anyone else have this problem ?
(4)Am I on the right track here with this problem.

I've attached a picture of what I assume is the valve in question.

Any advice would be greatly appreciated.

Thanks from sunny Kamloops
Neale

[tonydca]

From the looks of it, you have removed the spring-loaded overpressure popoff valve at the rear of the intake manifold.

The actual wastegate is lower down next to the turbocharger, attached to the exhaust manifold. An actuator rod from the turbocharger assembly opens the wastegate when maximum pressure is reached, and the valve you show in the picture is designed to pop open at around 13 psi as a backup relief valve if the wastegate fails to operate.

I was having the exact problem you described when I first got my van, and it turned out that the popoff valve was gummed up with years of black goop that had been entering the intake manifold from a faulty EGR valve. The goop was preventing the valve from seating properly, and it would open at around 5 psi or so. One of my telltale symptoms was that the firewall on the rear of the engine compartment near the popoff valve became speckled with little flakes of soot spitting out when the valve opened.

The fix in my case was to:

- exercise the popoff valve manually with the engine running and work it around to clean the deposits off the sealing surface,
- blank off the EGR to prevent more soot from entering the intake manifold, and
- install a $25 Princess Auto boost gauge to keep an eye on intake manifold pressure and turbo/wastegate operation.

[RichD]

I have heard of the part that minicarz has identified producing the symptom he described although I would start with what Tony is suggesting. As for adding a boost gauge, you can just plug a cheap handheld analog gauge into the system for tuning and save your money for more important gauges in the dash.

Regarding the part illustrated, the last time I checked a replacement is about $90. I saw a curber who didn't want to spend the $90 or delay a sale just replace it with a pipe thread (!!) plug. This, of course, was A Bad Idea - particularly because he didn't intend to tell the buyer of the van about it. But if you want to troubleshoot/isolate without a spare, a nylon plug would do in a jam.

[minicarz]

Thanks RichD and Tonydca for the great info. I'll dig deeper and take a look at the actual wastegate valve too. The popoff valve when I took it off was amazingly clean and there is no indication on the firewall of excessive soot. This popoff valve feels very easy to open to me so this may be the problem , but I'll check the wastegate valve, and even try blanking the popoff valve opening. to narrow down the possibilities.
Thanks again guys , I'll let you know the outcome/fix
Cheers,
Neale

[RichD]

While you are in there, if you could snap some pics... there isn't enough of that on here.

[Diver]

It could be that the over-pressure valve (pictured) has become weak, but if not check the wastegate actuator rod. It's common for these to seize but easy enough to lubricate and free off.

[Manitoba deli]

but I'll check the wastegate valve, and even try blanking the popoff valve opening. to narrow down the possibilities.

Don't blank off the popoff valve, it is there for a reason. If your waste gate is malfunctioning and allowing the turbo to build too much pressure, you can cause damage. Tee a pressure gauge into one of the small boost lines on the turbo and see what your pressure is at. This will tell you what needs fixing or replacing. Less than 12psi=faulty pop off valve, more than 12psi=faulty waste gate or actuator.

Jason

[minicarz]

Excellent information from everyone, thanks very much. I'll give it a go this weekend and relay the results. I'll try to get some good pictures to post documenting the problem and hopeful fix.

Diver what lube do you recommend for the actuator rod? Wouldn't that just burn off?

Cheers,
Neale

[Diver]

The usual method is to unbolt the actuator and wiggle the rod backwards and forwards while spraying lots of WD40 or other penetrating oil at the far end of the rod. After its been unseized the oil will burn off yes, but the rod will stay free (hopefully!)