NO vacuume but still need to drive

[mobilevet]

According to my checking, I've got no vacuum from my vac pump.

This means that my turbo wastegate will NOT OPEN?? right?

Can I still drive it safely if I just go easy 55-65 mph and do not towing?

Should I try to open up the wastegate a little by pulling back on the current linkage and somehow getting it to stay there??

I have a Heath Turbomaster on the way, but it will be a couple days until it gets here... once it does the vac pump is scrap, I already have a 101" belt.

Thanks.

[DmaxMaverick]

No vacuum means the wastegate will NOT CLOSE, and you'll have no boost. You'd be better off if you wire the wastegate closed, and drive conservatively. No boost will waste fuel and dramatically increase EGT's, even at moderate loads, like highway driving. If you don't have gages (boost and EGT), it's a crap shoot either way. One thing to consider, from an engine protection point, is the PCM will reduce fuel if you have overboost (and set the SES), but will do nothing for over-temperature (except let the engine cook until it quits).

[mobilevet]

Oh, brother.... I must have misread this article (http://www.thedieselpage.com/features/boostact.htm). I thought that the wastegate held the gate closed thereby giving boost and then pulling the gate open to relieve the boost pressures... okay - I was wrong.

So, as the wastegate actuator sits now (say the truck is not running) it is in the OPEN position (therefore NO boost), so I need to pull back on the rod and somehow hold it in that position so that the gate is CLOSED and there is boost.... then worst case it over-boosts and the PMD defuels until I stop, turn off the motor to reset it, and then I should be able to crank back up.

That right?

[mobilevet]

BTW - During all this loss of vacuum I have had ZERO smoke... is that to be expected???

[mobilevet]

RE: wiring the wastegate closed

Okay, let me be sure I've got this straight:

1- the wastegate actuator has the rod connected to the wastegate at the end closest to the FIREWALL
2 - the wastegate actuator has the "bellows" (large round container) end closest to the HEADLIGHTS (front of the truck)

Now, which way do I wire it? Do I pull the rod toward the front of the truck or push it toward the back?

(I'm asking because as it stands right now, I can move the rod either way and it just sits there, don't know if that's normal or not)

thanks

[DmaxMaverick]

It should smoke like a freight train without boost under load. All the fuel, too little air to combust it efficiently. If you have no vacuum, and it isn't smoking under heavy load, there's a piece of the puzzle missing. How did you verify your vacuum pump has failed? It should have 20-25" vacuum at the pump outlet, and about 15" at the wastegate actuator when it's operating (trying to hold boost).

To temporarily close the wastegate, you can use wire (bailing or mechanic's wire, etc.) to secure it. The object is to hold it closed (pulled and secured forward). The Heath Turbomaster does the same thing, only with a spring (instead of a stationary wire) to allow it to open when exhaust backpressure overcomes the spring load at a set boost level.

[mobilevet]

Okay - thanks. The vacuum pump is off and the wastegate is wired so that the rod has been pulled forward (i.e. toward the headlights).

RE: missing piece - yes, I was wondering the same. I guess going with the turbomaster will at least eliminate that piece and all associated vacuum questions. This problem started on another post as a Code 78, here is what I wrote after trying to measure the vacuum:

Well.... finally got time to check that vacuum and either I did something wrong or there is no vacuum. Best I can see, there is a very short rubber hose coming off of the round part of the vacuum pump (diaphragm?) and then another hose coming off and going to the switch/sensor located at the rear right of the motor where from there another hose goes to the turbo. I put a T about 8 inches from the vacuum pump in the hose that goes to the switch/sensor, about where it dives under the thermostat crossover. Since I got nothing (no reading and the gauge does work if I suck on it) I hooked the gauge directly into the previously mentioned hose and still got a goose egg reading.

I don't know why I got a zero reading and no smoke, it was a brand new gauge and seemed to work... only thing I can think of is that the gate was at least partially shut, but it sounds like the normal pressures tend to want to open it and that that would be unlikely...

The only other issue is that I have a very annoying chirp (not a squeal) coming from the belt. I thought that it would stop after removing the vac pump, but it hasn't. It sounds as though it might be coming from the harmonic balancer... could that be? I felt all over it and didn't feel any bad spots (chunks of rubber missing, obvious cracks, etc) but when I watch it spin, there is a bit of a wobble to it.... suppose it needs replacing?

PS - I've already put on a new tensioner and waterpump (see below)... that leaves the PS pump (which seems fine when I spin it) and the HB right?

[DmaxMaverick]

The balancer is a very sticky subject. My suggestion is, if it takes more than about 5 minutes to confirm it is good, replace it. If it wobbles, replace it. If you have doubts, replace it. They are costly, but a lot less costly than an overhaul or new engine. Don't know about the squealing. Could your water pump be on the way out? PS pump? A/C clutch bearing? Dragging alternator? Isolated crank pulley? Hard to say w/o getting hands/eyes on it.

A weak vacuum pump can cause differing results. Low vacuum can result in low or no boost. No vacuum results in no boost. The exhaust backpressure is many times more than resultant boost. Unless your wastegate or linkage is obstructed, it should blow open easily (under exhaust pressure). The bellcrank should move very easily by hand with the engine off, or with only the resistance of the actuator if it's connected.. If it's sticky or hangs up whey you try to move it (with the actuator disconnected), it's obstructed. The shaft could be galled or fouled (soot), or it could be damaged or fouled internally. If that's the case, it could explain a lot, including your DTC 78. You could also have a broken or leaking line/connector in your vacuum system. If you verify no vacuum directly off the pump with engine idling, the pump is bad, in any case.

[mobilevet]

.... I wonder if this has any bearing... when I bought the truck (4 mo ago) it already had the 101" belt on it. I didn't know it until I redid the coolant system and bought a new belt to go on it. They gave me the correct belt (the 102") belt which when I put it on immediately began to sing like a lark. I could put the old belt back on and the chirp would stop. I compared the belts and saw the difference. I went back and told the parts place that they gave me the wrong belt and they gave me the shorter one. Problem was that when I put the new 101 on, it chirped too... so I just put the old belt back on and the chirp went away... until it was ripped to shreds one day. Fortunatly I had the new 101 in the truck and was able to simply put it on and keep going. I tried to take it to my mechanic to see if he could tell where the chirp was coming from but it was very intermittent. Best he could tell was that it sounded like the area of the vacuum pump or HB. So, I just went on with the intermittent chirp until recently when the code 78 came up and I thought that it was probably due to the vac pump and decided that it was time to do something about it. That is also when I reallzed that the 101" belt was the wrong belt if the vac pump was still on (I wondered why you had to really crank back the tensioner to get it on!).

So, here I am now with the vac pump off, the 101 belt back on, new tensioner (kind that doesn't have ridges on the edges of the pulley, so I figure it isn't causing the chirp), new water pump, AC compressor spins fine, PS pump seems to also, and I still have a chirp!:confused:

[mobilevet]

FWIW - anytime I have ever manually moved the WG actuator rod it has always moved back and forth very smoothly...????

How would I determine if:
The shaft could be galled or fouled (soot), or it could be damaged or fouled internally

[DmaxMaverick]

FWIW - anytime I have ever manually moved the WG actuator rod it has always moved back and forth very smoothly...????

How would I determine if:
The shaft could be galled or fouled (soot), or it could be damaged or fouled internally
If it moves easily and smooth, it's not obstructed. At this point, I suggest you "get by" until your TM is installed. Chasing a problem with your wastegate when all the parts are not working is a ghost chase.

You need to verify the routing of your belt. The tensioner should not have grooves in it. It should contact the BACK of the belt. If it does not have grooves, and is contacting the grooved part of the belt (and vice versa), it won't last long. It could also explain the confusion of the belt lengths and squeal. Consider this: grooved pulleys contact the grooved side of the belt, and smooth pulleys contact the back of the belt. Mix/match this, and the belt will fail, and also explain the squeal. The only pulleys that should be smooth is the water pump, tensioner, and perhaps one of the idler pulleys (depends on the configuration). This is "off the cuff", as it's been a long time and many other vehicles since I've been under the hood of a 94. Others with a 94 handy can verify this for you.

[mobilevet]

I'm sorry... I think I confused the issue. What I meant was that the pulley wheel on the stock tensioner had it's edges turned up a bit so that the belt rode between them, while the aftermarket one that I put on was smooth all the way to the edge. Neither one had grooves in it.

Re: HB - is it possible that the pulley is bad but the balancer is not? Or should I just replace both of them? I'm now thinking that the wobble I saw was too much for my comfort. Any problem using an aftermarket balancer, or should I get one from GM?

thanks


PS - good advice on the turbo... we'll revisit that after the TM is installed.

[DmaxMaverick]

It is possible you have a bad pulley and a good balancer. But, you should feel comfortable with their condition. Confirm the balancer is good, or replace it. There really isn't a lot of room here for error. If the pulley is wobbling, it needs to be replaced, in any case. I really can't say one way or the other on the aftermarket balancers. Dorman used to be mfg in the US. Now they're not. But, I haven't heard of an unusual Dorman failure, then or now. It's probably OK, I just can't say if it's as good as an OEM. Check the price on one at www.gmpartsdirect.com, and compare that with your local source. Many times, their price will be close enough to the aftermarkets it is worth a few bucks for the piece of mind. Same goes for the pulley, as well as many other parts.

On the tensioner pulley, it makes no difference whether it's channeled or not. As long as the belt rides centered, it's OK.

[mobilevet]

I've got it torn down to the pulley/balancer now. There was not really any vibration problems so maybe the balancer is okay. I'll pull the pulley and see what they both look like. It will for sure be replaced. I'll for sure replace the pulley.

Will I need a puller to get the pulley off?

I have seen the little "tool" for putting the balancer back on, but if I have to replace the balancer l'll need a puller for that also right?

thanks

[mobilevet]

Well the pulley's off... guess that answers the question about needing a puller - you don't.

Doesn't look to bad to me, but there is some dry rot of the rubber part... I'm going to try and post pictures.

My local aftermarket guy says that his pulley is $51 - the GMDirect is $151! What gives? Maybe my local guy has the wrong part???? Guess we'll see tomorrow.

Since pulling the pulley was so easy, maybe I'll try just replacing it first... what exactly should I be looking for to determine if the balancer is bad?? anything visual?? or just vibration problem (which I don't have - I think).

thanks

[mobilevet]

Okay...I've tried to attach pics of the pulley...looks pretty good to me.

[DmaxMaverick]

The rubber on the balancer is critical. Any part of it that is too hard or too soft, or if any of it has extruded, it's bad. The balancer will not usually cause a noticeable vibration before catastrophic failure. It's job is to balance the engine's internal harmonics. Inspect it very closely. I couldn't tell anything by the picture you posted (too small). Cracked rubber on your pulley indicates it's bad. It is possible your aftermarket supplier is offering a non-isolated pulley. Don't save money here, if that's the case.

Normally, a balancer puller is required. If yours came off too easy, it could be bad for that reason alone. Else, the crank is damaged. The tolerance should be very close.

[mobilevet]

"non-isolated"?? You lost me there. How do I know the difference?

I'm sorry that I'm so ignorant about this. However I do want to learn.

Actually, I don't have the balancer off yet - just the pulley. Guess I'll have to pick up puller when I get the pulley (I have the balancer and front seal coming from GMDirect). Any suggestions on a type of puller?

[rhsub]

non-isolated pulley is one piece construction all metal no rubber
isolated pulley has a rubber connection between crank hub and pulley
HB inspection; check condition of rubber strip between inner hub and outer ring, if its cracked, shifted out of place or isn't uniform shape all the way around replace it. If the outer ring has shifted forward or back replace it
The outer ring is bonded to the rubber strip and the rubber strip is bonded to the inner hub, should be NO evidence of movement or slipping between inner hub and outer ring
If in doubt REPLACE IT. the alternative is very costly BROKEN CRANKSHAFT
When installing a new HB always use the proper installation tool NO HAMMERS, quite a few good HB's have been ruined by installing with a 3 lb hammer
Good luck
Ron

[Warren96]

You can borrow a puller from many auto parts stores. Advance Auto is where I borrowed mine.

[mobilevet]

Thanks for all the tips... I'm still waiting on my turbomaster and then I'm going to get back on top of this... until them....

[DmaxMaverick]

You can borrow a puller from many auto parts stores. Advance Auto is where I borrowed mine.

You could. But, a good puller isn't expensive, and it's something you should have. Prices vary from $5 to $50 (US). A $5 puller won't pull many balancers. Most $10 pullers will. (prices are ballpark). $50 gets you a Snap-On that isn't really any better than the rest. Most of them can also be used to pull steering wheels and some pulleys. Very handy tool. For about $20, you can get a good "cheapy" with 4 slots (for bi's and tri's), that looks like a chicken foot, or a peace sign. They usually come with several different size bolts and punch adapters.

[mobilevet]

Okay... got the turbomaster on and seems to run good. Guess I need to check my boost pressure - right?

I'll search, but maybe someone could help me out here:

? Best to check the boost pressures while on the highway - or idle good enough?

? Best location to tap into with the pressure gauge?

Other tips??

Thanks

[rustyk]

You gotta run the engine with a load to get realistic boost pressures. Idling, even if you rev the engine up, won't tell you much.