Engine/Transmission (1994 - 1998) Finding Boost Leak

[MAleshire]

I purchased a truck about a month ago, and I have a boost leak. I need some help/suggestions on what to check and how to check it. The symptoms are no accelleration/power on the low end. At about 1600+ rpm I get boost and the truck takes off. With some helpful suggestions from a TDR member I looked at the AFC. I removed the plug over the star wheel and loosened the wheel to take tension off the spring against the diaphragm. I loosened it to what seemed to be the end of travel. I didn't seem to notice any loose parts or binding up of parts inside the AFC. On the test drive I got more accelleration on the low end but the boost guage didn't show a whole lot of boost until higher rpms. There was no noticeable smoke coming out the exhaust. I was told that this lack of exhaust smoke and some increased power most likely indicates a boost leak between the intake manifold and the AFC. The only thing between them is the little hose with the pressure fittings on each end. Anyone know how to test this? I've visually inspected it and didn't see any signs of wear or deterioration. Whether it holds pressure or not is in question. If that checks out OK I guess the next step would be the clamps and hoses between the intercooler and the manifold. Would the intake manifold gasket have any effect on boost leak? Again, any suggestions would be appreciated. I want to locate the source of the problem and not just start throwing new parts at it.

 

[JAmos]

You should check to see if there is a line that runs from the fitting on the afc to the turbo wastegate. If so, check this line for leaks as well since it signals the wastegate with air from the afc. If there is a leak in that line it will delay or constantly hinder proper movement of the afc.



Do you have a vacuum pump? You could take the line off the manifold and put vacuum to the rest of the lines and fittings that way and see if it holds. If you have a leak hopefully you should be able to hear it.



You could also buy a schrader valve(same as a tire valve stem) and a couple other fittings to make a pressure tester. That way you should be able to feel?hear air coming out and even use some soapy water to help pinpoint the leak.



Another possibility is the wastegate diaphragm having a hole, but I don't think thats going to be very likely, but... ... .....



Hope this helps.



Jordan

 

[MAleshire]

Thanks Jordan!!! I'll give your suggestions a try.



Skip

 

[Buck88]

I went to Home Depot and made a pressure tester for about $15-18. It helped me find a leak that I otherwise wouldn't have known of. But I can still hook up the tester and hear slight weapage from around the AFC area. Anyways, that tester helped out alot. If you want I can post a picture, and give you a parts list.

 

[MAleshire]

Thanks for the reply. Please post the picture and parts list. I'm starting from ground zero, and I'm sure I'll being using a pressure tester again.



Skip

 

[Buck88]

Ok, sorry it took so long, but I used a 4"-3" flexible coupling, 3" cleanout coupling, 3" cleanout end-cap, and air fitting. On page 30 of TDR issue 58, there is one similar. You may need a better clamp though, cause mine blew off at a regulated 15psi.

 

[MAleshire]

Thanks for the pictures and the info. I'm in a holding pattern til I figure this thing out. Also, I'm at the mercy of the weather so I can work outside on the truck.



Skip

 

[Dave M]

I had a bad boost leak on my 97. It was on the passenger side of intercooler where a short rubber boot connects the intercooler to the steel tube going up to another boot connected under the tubocharger. The bottom boot was rubbing against the inside lip of the fender and caused a 3 inch slice in it. I could not see it until I disconnected the boot and pulled it out.



Here is a link to a post that I posted a pic of the torn boot (look in post #5 & 10):



https://www.turbodieselregister.com...998/128356-low-boost-problem-please-help.html



Dave

 

[MAleshire]

Dave----thanks for the info. I just got to thinking about the oil analysis just done. There were abnormal levels of silicates. I replaced the air filter which looked in good shape. I think a hole or rip in a boot would allow entry of dust or dirt as well as cause a boost leak. I've visusally inspected the boots. Now I need to take them off and take a look.



Thanks, Skip

 

[Dave M]

Dave----thanks for the info. I just got to thinking about the oil analysis just done. There were abnormal levels of silicates. I replaced the air filter which looked in good shape. I think a hole or rip in a boot would allow entry of dust or dirt as well as cause a boost leak. I've visusally inspected the boots. Now I need to take them off and take a look.



Thanks, Skip

It's any easy fix to replace all 4 if that's where the leak is. Also you might tighten all the boot clamps while your looking. I taped my with duct tape till I got a set of 4 new ones for all the boots from Piers Diesel for about $200 a couple years ago. If you have a boost gage you'll know for sure. Otherwise you'll notice way more power pulling a hill.



Let us know what you find.



Good Luck,

Dave