[85vette]

I just bought my 98 C2500 for $1500.00. I think I got a pretty good deal. It needed a transmission and tires. It's the f motor with 210K miles on it. It runs good, A/C works good. A friend of mine looked it over for me ( I don't know a lot about diesels) and told me someone had bypassed the wastegate solonoid. He said that's why the truck has so much power and that this will not cause any damage. Is this so?

 

[Scrufdog]

thats bad. Could cause the turbo to go into overboost conditions if the vacuum solenoid has been bypassed. If that happens, you blow your motor and shred the turbo bearings.

Does the wastegate still have vacuum lines going to it? Look at the turbo (snail shell on the pass side) and look to see if there is a round diaphram or a spring on the little arm that sticks out of the bottom of the turbo. If its the diaphram type, and the vacuum lines are still there, the follow the vacuum line to the drivers side, on top of the engine, and see if it goes to a small solenoid, with another vacuum line, or if it is just 'jumped' to another vacuum line. The solenoid your looking for has a green dot on it.

MAybe take some pics if you can.

 

[85vette]

I looked on the turbo and it has a diaphram on the side with a vacumn line coming out of it going over the top of the motor. On a bracket is the solonoid with the green dot with two vacumn ports that is hooked up to nothing. Also, next to that is a wiring harness with an identical solonoid attached to it. This also has no vacumn hoses on it. The vacumn line from the turbo goes right by the solonoids and is an orange line with a small "dog leg" black rubber piece....not sure if there is a vacumn port in this piece or not. The line then goes toward the front of the motor and down behind the altenator. Sorry, I don't have access to a camera. Do you have a picture of one that is hooked up correctly? I have no idea how long this has been hooked up this way but there must be a problem as two solonoids are on the truck yet neither one is hooked up. Also , I am not getting a check engine light. Thanks for the help.

 

[Scrufdog]

ok good job gettin info.

Now...

The orange and black vacuum lines are supposed to be plugged into the green dot solenoid with a rubber boot. I'd guess that at some point the solenoid went bad and whoever owned that truck rigged it with a bypass. Bad move for a permanent fix. Go find the guy and smack him. This may have caused premature engine and turbo wear.

To fix this you have a couple options.

1. Go to the dealer and spend the $35 for the boost control solenoid, and whatever it costs for the black boot, replace.

2. Buy or build a manual wastegate control. If you go with that option you will first need to get at least a boost gauge so you can properly set the boost levels. An EGT gauge is also highly recommended to keep things under 1250 degrees. Set the max boost for 8 PSI so the computer doesnt freak out.

I take it the engine code is an "S" VIN since you mentioned a 2nd solenoid. This solenoid is meant to control the EGR valve that should be on top of the upper intake manifold.

 

[85vette]

It's an F motor, the second solonoid is identical to the one on the bracket, I'm thinking they bypassed that on with another one. Both of them have green dots on them. It sounds like I need to get a new solonoid for the time being. Is there an advantage to having a manually controlled wastegate? I plan on towing a Gooseneck with Massey 240 with a loader and other equipment. I have been using my 1988 C2500 with a 350, 5 speed but it's really hard on the gasser, hoping I would see a big improvement with the diesel.

 

[DavidPhillips]

sounds like you just need to hook the vacuum lines to the solenoid there with the green dot on it. The one that is connected to the wiring harness. See if that works.

 

[DavidPhillips]

Diagram

 

[Turbine Doc]

85 Vette welcome to the site :welcome2:

2nd solenoid ??? most F's have only 1 solenoid sounds like you have a F with EGR it gets a little trickier to bypass vacuum controls; S engine that yr should have a bank of 3 solenoids,
what is 8th digit of VIN, S or F, pics also will help.

$1500 for a functional engine isn't bad, provided that is what you have, since you are 2wd which makes it a little easier, drop the oil pan and check the main bearing webbing for cracks, a fairly easy check to determine if it's even worth going further with TS vac issues, if bottom is toast we have bigger issues than vacuum accessories.

In the FAQ picture area is a pic of a 98 S engine vac hose routing sticker, see if you have same sticker under your hood.

Lastly take a minute to update your signature line for us please see info how to do it in my or any other 6.5 moderators signature line

 

[96GMC6.5L]

Would bypassing the selenoid like this alow me to test my boost gauge by going straight from the pump to the actuator? Someone told me that this would hold the wastegate tighter than with wire, allowing for better more accurate results.

Keep in mind this is just to test my boost gauge. I will not be keeping it premanent like this.

Thanks, Jacob

 

[Turbine Doc]

Only if your vac pump is working, have you determined via FAQ tests that you even have vac present from pump.

Jacob rather than jumping thread to thread stick to your original one and let us help you through it, I know it may seem slow to get a reply sometimes, but remember we have lives out here to lead as well so be patient, jumping post to post makes it hard to track if conditions are worsening or getting better in your case, rather thatn diluting someone elses question with your sitiuation,

you are overthinking the problem. You have a pump that is supposed to make vacuum when it goes roundy roundy; check the main line that comes from the pump to the solenoid bank see if it has vacuum if not you need a new pump; that simple. If you have vacuum there then we need to look at why you don't have it before and after the solenoids when you are supposed to have it. Look at the FAQ for waste gate then come back with findings with an update in your original thread.

 

[85vette]

Can you buy the wastegate solonoid any where besides at a dealer? My local dealer wants $49.83 for one and I've been told it's a 30-35 dollar part. Not trying to be nitpicky, but this dealer is known for ridiculously high prices.

 

[Dan Hunter]

Try rock auto online.

 

[Scrufdog]

well, if you have 2 there on yours, and both have green dots, might as well try them both to see if one is good.

 

[85vette]

Scrfdog, what will it do when I hook it up if the solonoid(s) are bad?

 

[Scrufdog]

you wont get boost, no more than maybe 2 psi at full throttle, and your Service Engine light may come on.

put your truck info in your sig

 

[85vette]

Alright, I plugged the orange vac line into the front of the black rubber receptacle and plugged the receptacle into the wastegate solonoid, fired her up and she drives just like she did before I hooked it up right. It seems plenty powerful to me. I don't know why someone would bypass this solonoid if it works this good. Any chance it could heat up and stop working right? Maybe that's why they bypassed it in the first place?

 

[DavidPhillips]

They most likely bypassed it to remove the control of boost from the computer.

It's best to leave it in the control of the computer unless you have gauges and a need to modify it.

 

[85vette]

Thanks for the help guys, there's a lot I don't know about diesels but I'm learning, I think I understand the advantage to manual control on the boost, but does the computer perform that poorly? I would like to get a lot of miles out of this truck. I see some of you have boosted the performance of your own trucks. Once I get a little more comfortable with this one I might want to improve mines performance as well. Right now reliability is the goal. Thanks again!

 

[DavidPhillips]

The computer works well at keeping it at a safe boost level and lowers boost according to coolant temperature and intake air temperature as well.

The vacuum control is capable of working much better than a spring. It does exactly what the computer wants it to.