95 Suburban strange problem

[serluk63]

Sensation. I start the engine. While the car cold brakes fine, a steering wheel easy, the car goes easily, the car soft, swallows of any roughnesses. Gradually there is a sensation that something prevents to go, as if the pedal of a brake is slightly pressed or wheels are lowered. Thus brakes become worse, and the steering wheel is a little hard. The car goes hard, on roughnesses of road the car skips and shivers. And suddenly, at speeds approximately 70 miles I feel small shock and the car becomes soft and quick. Sometimes the car left hard. What is it? I think that hydroboost or hydro pump is defective. But It can be differential, transfer case or ...

 

[serluk63]

Asking and answer question by myself. Flushing of hydro-boost solve the problem. I change oil in hydro-boost for several times by pushing brake pedal.

 

[btfarm]

Glad to hear you got it figured out!

 

[just a number]

nice easy fix. that's what we like to hear.

 

[serluk63]

Thanks for your replies, but I really don't understand how hydro-boost can make this effects. If brakes was blocked a little, then wheels must overheated, but when I touch the wheel by my fingers fell hot but not very hot. Rear wheels was not hot but warm.

 

[serluk63]

What oil I have to use in hydro-boost. About red transmission fluid I know, but may be somebody knows another. For example, I know that Citroen use for hydrosystem special fluid (green for old cars and red for today cars).

 

[Ed HD]

In these vehicles I've used Transmission fluid with no issues. There is specific power-steering fluid, but I don't think there's a big difference.

 

[dangerousdave]

Since the Hydroboost and Power steering use the same system, and both are critical, I used the best power steering fluid (Valvoline) I could get, flushed it by Missy's procedure right before rebuilding the hydroboost unit.

It's been a while, I'll look for the link/thread.
On edit; here is one. Not Missy's but close enough. Keep flushing until it comes out clean. Fluid is cheaper than a crash.

http://www.thetruckstop.us/forum/showthread.php?t=7865&highlight=hydroboost

мы радостны иметь вас.

 

[serluk63]

Hello. Unfortunately, I had problem with my transmission, forward drum broken. I have repaired transmission this month. But now it seems to me that engine speed and car speed is not correct. Is somebody knows what engine speed must at speeds 60, 70, 80 miles per hour.
Another question: Sometimes when I am going on highway at speed 60 -65 miles/hour check engine lamp comes. I take my leg away from gas pedal for a moment then check engine lamp goes out. I press gas pedal again then check lamp comes again. Trouble Code is 1178. What I have to repair?

 

[NVW]

That code doesn't show up in here:http://www.thetruckstop.us/forum/showthread.php?2657-A-little-help-here...&p=50700#post50700

We need to know your tire size, rear end ratio and rpm's at 60 mph to know if your speedometer is correct.

 

[serluk63]

Thanks for information. My code 78. I have 2500 4x4 vin "F" Suburban. I want to know if my speedometer show 75 mph, what must be engine speed. I think that in this case I dont't need real speed.

 

[WarWagon]

DTC 78 - Turbo Wastegate Solenoid Fault

Blowing black smoke? Check vacuum pump for a vacuum. Check vacuum hoses. Check solenoid for electrical resistance.

 

[NVW]

with 4.10 rear end ratio you should have about 2250 rpm's at 60 mph, tire size will make a difference.

 

[serluk63]

To NVW: Thanks. I will check rpm.
To WarWagon: Question : Can I apply 12 V to solenoid to check it? Or I have to measure resistance. There is no a lot of black smoke. Thank You I will check vacuum pump first.

 

[NVW]

If you grab the waste gate lever while the engine is at idle, it should be very difficult to move. It should move freely with the engine off.

 

[serluk63]

Vacuum pump is dead. I check rpm at 60 mph, I have 2250 rpm.