91.5 with hard brakes when cold???
Thread Starter
Registered User
Joined: Mar 2005
Posts: 6,259
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From: Utah
91.5 with hard brakes when cold???
Hey guys my dad has a 91.5 cummins and when ever the temps cool off the brakes go hard until the truck runs or drives for a while/warms up.
I am thinking that the vacuum pump is getting lazy but I thought I would ask what you all think it could be???
I have not read the vacuum pump rebuild in the sticky yet but I noticed it said it was for a non intercooled truck... so are they the same as far as rebuild or are they different??
thanks for any tips or info you got
I am thinking that the vacuum pump is getting lazy but I thought I would ask what you all think it could be???
I have not read the vacuum pump rebuild in the sticky yet but I noticed it said it was for a non intercooled truck... so are they the same as far as rebuild or are they different??
thanks for any tips or info you got
Registered User
Joined: Oct 2005
Posts: 6,457
Likes: 95
From: KENTUCKY
Hey guys my dad has a 91.5 cummins and when ever the temps cool off the brakes go hard until the truck runs or drives for a while/warms up.
I am thinking that the vacuum pump is getting lazy but I thought I would ask what you all think it could be???
I have not read the vacuum pump rebuild in the sticky yet but I noticed it said it was for a non intercooled truck... so are they the same as far as rebuild or are they different??
thanks for any tips or info you got
I am thinking that the vacuum pump is getting lazy but I thought I would ask what you all think it could be???
I have not read the vacuum pump rebuild in the sticky yet but I noticed it said it was for a non intercooled truck... so are they the same as far as rebuild or are they different??
thanks for any tips or info you got
A decent dash-mount vacuum-gauge is in-expensive and simple to install, and will pay for itself, over and over, as a constant monitor of vacuum system health and well-being.
Complimented with a decent hand-held portable vacuum-gauge, vacuum problems can be pin-pointed in a process of elimination.
There are three different vacuum-pump designs on 1st Gen. trucks.
The earlier trucks have a twin-pod diaphragm pump that is fairly bullet-proof and, when split into two seperate systems, makes plenty of vacuum for the trucks needs, and also a big vacuum-over-hydraulic trailer brake system.
Later trucks have an entirely different VANE-pump system.
We never had much success getting these to support the needs of a vacuum-brake equipped trailer, necessitating the need of a seperate belt-driven pump for the trailer system.
This goes along with your question and I posted a link to a source for pump parts and kits:
https://www.dieseltruckresource.com/...d.php?t=176088
Some good information on that pump site.
DTR's "Cooler than ice cubes 14 miles North of North Pole" member
Joined: Oct 2006
Posts: 1,797
Likes: 9
From: 14mi North of North Pole
Pop the big plug off the brake booster. Cover the open end of the line with your hand. Runn the truck for a minute or so and shut it off. If the system holds vacuum you probly need a booster. I know I do. Mine leaks but works well untill it gets cold outside then the leak really shows and my brakes get hard.
Thread Starter
Registered User
Joined: Mar 2005
Posts: 6,259
Likes: 1
From: Utah
A decent dash-mount vacuum-gauge is in-expensive and simple to install, and will pay for itself, over and over, as a constant monitor of vacuum system health and well-being.
Complimented with a decent hand-held portable vacuum-gauge, vacuum problems can be pin-pointed in a process of elimination.
There are three different vacuum-pump designs on 1st Gen. trucks.
The earlier trucks have a twin-pod diaphragm pump that is fairly bullet-proof and, when split into two seperate systems, makes plenty of vacuum for the trucks needs, and also a big vacuum-over-hydraulic trailer brake system.
Later trucks have an entirely different VANE-pump system.
We never had much success getting these to support the needs of a vacuum-brake equipped trailer, necessitating the need of a seperate belt-driven pump for the trailer system.
This goes along with your question and I posted a link to a source for pump parts and kits:
https://www.dieseltruckresource.com/...d.php?t=176088
Some good information on that pump site.
Complimented with a decent hand-held portable vacuum-gauge, vacuum problems can be pin-pointed in a process of elimination.
There are three different vacuum-pump designs on 1st Gen. trucks.
The earlier trucks have a twin-pod diaphragm pump that is fairly bullet-proof and, when split into two seperate systems, makes plenty of vacuum for the trucks needs, and also a big vacuum-over-hydraulic trailer brake system.
Later trucks have an entirely different VANE-pump system.
We never had much success getting these to support the needs of a vacuum-brake equipped trailer, necessitating the need of a seperate belt-driven pump for the trailer system.
This goes along with your question and I posted a link to a source for pump parts and kits:
https://www.dieseltruckresource.com/...d.php?t=176088
Some good information on that pump site.
Thanks for your help tho
Pop the big plug off the brake booster. Cover the open end of the line with your hand. Runn the truck for a minute or so and shut it off. If the system holds vacuum you probly need a booster. I know I do. Mine leaks but works well untill it gets cold outside then the leak really shows and my brakes get hard.
man I also read the hydro boost conversion thread!!! to me that seems like a cheap and easy route to get BOMBER brakes. It's hard to beat hydroboost brakes
Thanks for your help guys
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