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Truck is a regular cab, 208,000 miles. Brakes work well but pedal could be firmer. I was just wondering if I needed to replace the master cylinder or if you guys think the leak is coming from the hydro boost unit. Was going to order the updated LLY AC Delco 2011 just want to make sure. All brake lines have been replaced on the truck

Looking for some help thanks guys. I have been lurking for awhile
 

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Pretty common for the brake booster to leak, it's a widely available part. I'd put money on the booster leaking and your master cylinder being fine.
 
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If it's leaking brake fluid then it's the master cylinder, if it's leaking power steering fluid then it's the hydroboost. Just search for a hydroboost for a 2011 but the brake pedal hole has to be enlarged.
 

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Truck is a regular cab, 208,000 miles. Brakes work well but pedal could be firmer. I was just wondering if I needed to replace the master cylinder or if you guys think the leak is coming from the hydro boost unit. Was going to order the updated LLY AC Delco 2011 just want to make sure. All brake lines have been replaced on the truck

Looking for some help thanks guys. I have been lurking for awhile

The Boost is so easy to change. Do it first run it and see if indeed the master is leaking at this time. Just FYI
 

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The Boost is so easy to change. Do it first run it and see if indeed the master is leaking at this time. Just FYI
Roger that thanks guys. I just bought the truck over the summer . I replaced the upper control arms lower ball joints idler arm pitman arm it seems to drive pretty good and I'm happy with it. Here's a picture anyways I figured out on myself with knowledge. Get old school and go on to the forums.

I will keep you updated if I have any questions on that I'm pretty sure I'm going to flush the power steering fluid first.
1082117
 

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I have another question the spare was gone out of the truck so I have ordered the hoist kit and I have acquired a new spare tire it's brand new. The tires on the truck are $265/70r17s the spare is a 225/70/r16. Do I just run that size tire as my spare and don't put it in four-wheel drive or should I get a tire that matches the size. And will the big 265 even fit up in where the spare tire goes.
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Not sure on the spare tire size. But I will say that I replaced the hydro boost on my LLY a while ago and it was easy.
Also, my t-case pump just rubbed through the case at 200k miles. So keep an eye on that if you haven't addressed it already.
 

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Discussion Starter #10
Not sure on the spare tire size. But I will say that I replaced the hydro boost on my LLY a while ago and it was easy.
Also, my t-case pump just rubbed through the case at 200k miles. So keep an eye on that if you haven't addressed it already.
I will keep an eye on it the truck is extremely clean underneath no leaks at all. I will have to look into that and do some further research.
 

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I will keep an eye on it the truck is extremely clean underneath no leaks at all. I will have to look into that and do some further research.
Its a bit tricky to spot since it doesn't really leave a puddle on the driveway, it just sprays all over the underbody.

Anyways its not terribly difficult to drop the case and split it to replace the pump with the Merchant Auto upgrade. Getting it back in is kind of a pain.
 

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Its a bit tricky to spot since it doesn't really leave a puddle on the driveway, it just sprays all over the underbody.

Anyways its not terribly difficult to drop the case and split it to replace the pump with the Merchant Auto upgrade. Getting it back in is kind of a pain.
Your words scare me big time. I went to go rotate the tires and to be honest my driveway is old and placed the truck on the jack stands and heard all types of creaking and settling going on. I'm really not comfortable getting near the truck like that I need some big ass logs and some pieces of wood or something. I have a harbor freight 3 ton daytona jack that's fairly new she seems to be at max lift to get the tires off the ground from the cross member of the frame in the front.
 

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If you get a flat in the back you will need to swap a front tire to back and put the spare (different size tire) up front. I believe you can damage the rear end driving on two different height tires
 

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For the slightly smaller spare, since it's just a spare to be used in an unlikely future event...
  • if you only have to go a few miles, then no problem.
  • if you have to go a significant distant, then only put it on the front. So, if a rear goes flat, you have to move a front to the rear, and the spare to the front. And as you said, avoid 4wd (unless needed just to get out of whatever).

On any vehicle off the ground, I usually prop it in 3 ways if there any chance of a failure. Jack stands, some other form of wood blocks stacked up, plus leaving the jack in place. I take some weight off the jack so in the best case there's some load on the jack stands and/or wood blocks. And of course, on level ground, and give the truck a sideways shove to make sure it's totally secure. If possible, only raise it enough to do the job so any drop doesn't land on you. For the t-case, you might not have to raise much (I don't know for sure because I did mine on my brother's lift). Do it safely!!
 
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Your words scare me big time. I went to go rotate the tires and to be honest my driveway is old and placed the truck on the jack stands and heard all types of creaking and settling going on. I'm really not comfortable getting near the truck like that I need some big ass logs and some pieces of wood or something. I have a harbor freight 3 ton daytona jack that's fairly new she seems to be at max lift to get the tires off the ground from the cross member of the frame in the front.
I got rid of my harbor freight jack stands, so I did the t-case with the truck still on the ground.

But yeah, I don't like working under the truck while its on stands either. Plus, since I moved, my driveway is sloped, so I really couldn't lift it up there anyway.
 

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Discussion Starter #16
Hey what's a good price on the hydro boost? I'm having trouble finding where to buy one... I see a couple different part numbers people are using.
 

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I got rid of my harbor freight jack stands, so I did the t-case with the truck still on the ground.

But yeah, I don't like working under the truck while its on stands either. Plus, since I moved, my driveway is sloped, so I really couldn't lift it up there anyway.
You trying to tell me I should do the pump rub kit before she starts leaking.?
 

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Hey what's a good price on the hydro boost? I'm having trouble finding where to buy one... I see a couple different part numbers people are using.
Looks like you can get them for around $150 from Rockauto for a reman (without core charge), and just under $200 from Amazon. I bought mine from Oreilly, I think I paid around $230. I got Cardone part number 527371.

I'm seeing a GM part number 15854059 from gmpartsgiant and others, seems like pricing from online GM dealers is around $375-390 for new.
 

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You trying to tell me I should do the pump rub kit before she starts leaking.?
Some guys on here swear this is a part you want to do new. Although i didnt and sounds like maybe a few others didnt. Again im just passing on the info. I think they said it was due to receiving bad parts
 

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You trying to tell me I should do the pump rub kit before she starts leaking.?
It's a pretty good chance it'll rub through sooner or later. If you catch it and fix it before it rubs through the case, you're just paying for the kit. If you catch it after it rubs through, you're paying for a new case half at best, and if you don't catch it before all the fluid runs dry, you're buying a whole new transfer case.

I've had 4 GMT800 trucks. First one rubbed through and I got lucky and caught the leak it before it caused a problem. Still had to buy a case half. Second one I didn't own long enough to matter. 3rd and 4th ones I proactively opened the case up for the pump rub kit...both had broken clips and were in the process of rubbing through. So it's not a matter of if, but when IMO...and how much you want to pay when it happens.
 
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