Barn find, bad brakes, what am I getting myself into?

[katie]

There's a 1990 Turbo Grand Prix listed a few hours away that's been sitting in a barn for about 20 years. 130k miles. Cosmetically it seems like it's in pretty good shape (hard to tell the difference between clear coat issues and dust from the photos) but the seller mentions "I think it needs master cylinder rebuilt" and doing some research that sounds like a big problem for these cars...

I'm trying to understand what options I may have here and how much of a time and money pit the brakes will end up being.

Other known issues are tires, battery, and door handle linkage.

I haven't contacted the seller yet but I'm assuming it hasn't been started in a long time, so there's also the risk of discovering other big issues after getting things ready to try turning it over again.

They're asking $3500, but looking at the Bring a Trailer auction prices for running ones with less miles plus the brake issue I'm hoping I can talk them down quite a bit.

[55trucker]

Being a *TGP* the car will have the PMIII abs system. To repair that will cost you more than it's worth & it was a troublesome system........

is this a southern rust free car? has it been sitting on a concrete pad or in the dirt?

if sitting for 20 years expect a mountain of work to put it right.....

post up a few photos of the car, especially the underside.

 

[jiggity76]

15 hours ago, 55trucker said:

Being a *TGP* the car will have the PMIII abs system. To repair that will cost you more than it's worth & it was a troublesome system........

is this a southern rust free car? has it been sitting on a concrete pad or in the dirt?

if sitting for 20 years expect a mountain of work to put it right.....

post up a few photos of the car, especially the underside.

 

Well said and I think the region from which a car lives in more important than whether it's been sitting in the dirt or on a pad.

My Cutlass sat up in the original owners backyard for at least 9 years if not more.  It being a Southern Oklahoma car is the reason why it's not rotted as they don't use any salt in that area thank God.  Also, hello 55!

 

Edited November 14, 2023 by jiggity76

[katie]

Yeah, I'm aware about the PMIII which is why I brought the brakes up first. I see people swap out the entire system for a vacuum-boosted setup but actual details or parts lists seem to be few and far between. It's obviously a project, but it's hard to get a feel for just how big of a project it is.

It's an Indiana car. Only body rust I see is a bit around the antenna, but they don't have pictures inside the doors. Surface rust underneath but it looks a lot better than I'm used to seeing here in Michigan. It's pretty rural, so I'm guessing it didn't see much salt. Stored on dirt/straw, no obvious signs of rodent damage but obviously I'd be going over wire and every piece of rubber...

These things come up so rarely it's hard to judge the value but I'm convinced that they're asking way too much because of the amount of work, unknowns, and mileage. This post was mainly to feel out if it's worth reaching out to the seller for more details and pictures or driving out three hours to see it in person. But the more I'm thinking on it the less likely it seems like this one isn't the one to get even though it's nice cosmetically. The fact that it's been listed for over a month at this point likely means they're not entertaining lowball offers.

My first car was a '92 SE, this would have been a fun project.

I also realized recently that the back of these only seats two - it's not the bench I remember from the SE. Which kills the "I know from experience we can fit all three kids back there if we have to" argument for it having some practicality as a second car. Not something we would need often, but very nice to have as an option.

Edited November 14, 2023 by katie

[55trucker]

From my own personal *biased* opinion the engine would have to be able to crank ( i.e. not seized), the turbo would have to do the same, hopefully try to fire with the aid of some starting fluid up the intake snorkel. Expect the alternator to be seized, the coolant pump may be in the same boat, a careful inspection of all the plastic vacuum lines for their condition, the coolant hoses would need replacement, etc.

Expect to replace ALL of the brake components...calipers, rotors, flex hoses.

 

With regard to the PMIII...the master assembly is mounted to a firewall support that is not the same one used for the non abs system, if one wanted to convert the entire PMIII brake system to vacuum boost one would have to locate a regular non abs car in a salvage yard & go to the effort to disassemble all that is needed to pull that support to install into your project.

The chassis would have to be in really good condition, the paint the same......even then, if the powertrain needed an entire rebuild then in reality what you're purchasing is just a rolling chassis & would have to priced as such & the present owner understand that.

[K&R]

Similar situation with brakes. I have a Cutlass with the same PM lll system. Looking to convert to standard vacuum but not sure how to do that. I have heard the early F Body Camaro vacuum brakes are compatible to swap.  

[55trucker]

Not an easy job to do........

the entire W body brake system is unique to the W body.

No components transfer to or from any other carline.

If one wants to convert from ABS to non-abs you're going to find yourself hand fabricating all 4 sets of lines to all 4 corners.

The non ABS cars make use of 4 independent brake lines right off the master going to the 4 corners of the car, the ABS system doesn't follow this same procedure.

There are 3 main lines off the ABS module, 2 to the front, 1 to the rear where at the back end of the car one will find a proportional splitter to feed the 2 rear calipers.

The masters themselves are not interchangeable, one is dedicated for ABS one is dedicated for non ABS.

The booster is another hurdle, the vacuum booster can be readily had but what it is fastened to is another story.

As I stated in a prior thread one has to go to the effort to remove the heavy plate bracket that is part of the firewall that the ABS system, part of the A/C system & the steering rack column passes thru & go out & find a plate in a non ABS car such as this one in Jiggity's photo shows & pull it out to replace the one in your car. It's not a job for the faint hearted.

 

 

Edited February 15 by 55trucker

[White93z34]

I converted my 1990 TGP to Vacuum

I've previously converted a 1989 TGP to Vacuum

done it 2 different ways, the "right" way on the 1989 - Full OEM factory brakes with the correct firewall plate and 2 new rear brake lines.

Be advised, this results in the location of the master being VERY close to the turbocharger - my idea was to use a N body master as its basically the same one just kicked up at a different angle. never got around to trying that

you can re-use the front lines in all situations.

and on my own 1990 I used a 4g F body booster and master, mounted to an aluminum plate I made bolted to where the PMIII used to mount

You have to use the pushrod off the TGP and weld or otherwise attach it to the F body booster. I modified the front brake lines into a splitter and then made a line to go from the f body master to the splitter and then made a reducer of some sort for the rear line.

Doing this is OK if doing a f body setup, NOT ok for a factory setup. understand the differences between F/R Split and Dual Diagonal brake systems and use extreme care to ensure all lines go to the proper places on their respective master cylinders.

All this said I think both solutions are safer then using PMIII in the present era. It was a idea that was ahead of its time. Its full of single failure parts (that have been getting baked by a turbocharger for 30 years) that can leave you without brakes in the event of a failure - also parts are simply not available anymore 

[SuperBuick]

Question here - this topic and details have been so helpful. @jiggity76 and I are chatting right now on this very subject…

 

My question is - if (or when, really) converting a car that is powermaster 3 manual transmission to vacuum brakes, and knowing i have to swap that firewall plate (which I will have access to as I’m picking up a 1992 non abs car, but automatic), how do i make the 1992 firewall plate accommodate the manual. Is it just drilling a hole? Or maybe the hole is already there?  
 

thank you

[Bake82]

On 9/21/2024 at 9:01 PM, SuperBuick said:

Question here - this topic and details have been so helpful. @jiggity76 and I are chatting right now on this very subject…

 

My question is - if (or when, really) converting a car that is powermaster 3 manual transmission to vacuum brakes, and knowing i have to swap that firewall plate (which I will have access to as I’m picking up a 1992 non abs car, but automatic), how do i make the 1992 firewall plate accommodate the manual. Is it just drilling a hole? Or maybe the hole is already there?  
 

thank you

 

A hole is already there.  However it’s not correct in shape or angle on the plate. Many have cut the hole and made it work. (Auto is round and I believe angled slight upwards, manual has squared corners and is flat). 
 

I actually have a vacuum booster, manual plate I’d sell if you’re interested in it.  PM to chat more if you want!  
 

unfortunately you’d still need to dig into the dash as you’ll need a few pieces from vacuum setup I don’t have (mainly the rubber boots the vacuum booster push rod goes through). 

[SuperBuick]

On 9/23/2024 at 12:08 AM, Bake82 said:

 

A hole is already there.  However it’s not correct in shape or angle on the plate. Many have cut the hole and made it work. (Auto is round and I believe angled slight upwards, manual has squared corners and is flat). 
 

I actually have a vacuum booster, manual plate I’d sell if you’re interested in it.  PM to chat more if you want!  
 

unfortunately you’d still need to dig into the dash as you’ll need a few pieces from vacuum setup I don’t have (mainly the rubber boots the vacuum booster push rod goes through). 

PM sent - and thank you!!!