I've had this base 1990 C4 convertible for 26 years. It had 3K when purchased. The only major modification is a conversion to RHD in 2002 when I took the vehicle to Australia so the pedal is now on the opposite side of the car.. It now has 50K miles original. Brakes have always been "average" which I understand is normal for a C4. The bakes system was never modified (except for the RHD pedal/line conversion) until about 150 miles ago when the workshop fitted new ceramic composite pads all around, new drilled and slotted rotors all around, new brake master cylinder with standard 7/8" bore and fully flushed lines. All parts were new and came from the USA. The vacuum was down so the mechanic fitted a new Bosch (they now own PBR) electronic booster to the PBR vacuum system. The Bosch booster was fitted in addition to the original PBR system. This was the recommendation of the Bosch technician.
The pedal is firm and the vehicle stops in a straight line. The rotors were cleaned before install. The brakes have been "bedded in". The system has been thoroughly tested by the workshop and meets GM specs for vacuum and line pressure. The brakes have improved a little after the upgrade but are still not great for emergency braking. There is normal level of brake dust on the rims after use.
The pads removed 150 miles ago were Delco which I had fitted about 15Ks prior. They had minimal wear. Old rotors (removed) were the original standard rotors had 50k and minimal wear. The car is mainly used on country drives (not in the city).
Can anyone assist?

 

I put a new master cylinder in and brakes were hard to stop adjusted the rod on the brake booster and made huge improvement but don't go to far.

 

 

The rubber brake hoses are a common weak point. After years of use they can collapse inside, but still look fine outside.

 

I do not know. I would assume that is was at the master cylinder as its the easiest

 

I thought about hoses. We checked all the lines and they appear ok. If they collapse inside, would the be some sort of evidence on the outside?

 

Then your still left with 2 unknowns. #1 is the flexible rubber lines which was previously mentioned # 2 is the ABS. The flexible lines are easy and cheap enough to replace. The ABS is another thing altogether.

On a side note, if you don't mind mentioning, how is the RHD conversion done? How do you deal with the steering wheel and HVAC, the parking brake and gauge cluster being on the wrong side? I for one am very curious and would love to see pictures of the finished conversion.

 

Hi

My C4 has great brakes, does not require much effort at all.
The number one thing you need is high friction metal brake pads, without friction you can stand on the brake pedal and barely slow the car.
In OZ you can get Bendix ultimate brake pads, great for street and track.
Bendix ultimate
https://www.ebay.com.au/itm/Bendix-F...item2380711d89
Bendix heavy duty
https://www.ebay.com.au/itm/Bendix-F...D/152478751925

 

Yes, I am unsure about the ABS. I have not checked this out as yet and I will do so when I return to Oz later this year. It's one of the things I did not check-out fully. My thinking at the time was that the brake system should still function normally, even if the ABS is not functioning. It should lock up the brakes if the ABS was not operating. That's why I did not check it out earlier. I know that the ABS is not activated under heavy braking. Currently, under heavy braking, the wheels do not lock up or even come close to locking up on the dry black-top road surface. I'll try it out on grass when I get back to Oz to see if the ABS is working.
Unfortunately, I have no personal knowledge of the actual working of the ABS system. My thinking now is that perhaps if the ABS is malfunctioning, it maybe stuck in a position that releases the some of the normal full line pressure so that the brake system never gets full line pressure when it is under actual driving conditions.
The workshop did check the ABS thru the computer analysis codes and it showed that the ABS was functioning normally.
Do you have any additional comments about the ABS ?
Regarding your RHS conversion questions; I'll look to see if I have any pics with me of the interior and under the hood and I'll post them. If not, I'll take some and post them when I get back to Oz if you are still interested.
The steering uses the same steering box and in its original GM position. There is a new cross-over shaft running from the LHS to RHS of the vehicle. Its behind the dash and not in view. The links use universal couplings. The steering wheel is the GM original with driver airbag. The steering is tight and handling is normal for a 90 convertible. The dash was custom made and the gauge cluster is the same as original GM The dash configuration is the same as GM original. It looks identical to the original GM except it is mirror imaged. The RHS is all oriented/biased to face the RHS driver position so it's all the same, just changed to face the RHS instead of the LHS.
The HVAC required re-plumbing and extension of the wiring. The major conversion issue was that the main wire harness was not long enough to extend from LHS to RHS and this all required re-routing and extended using solder joints.
The park brake is the original and in the same position next to the driver's seat but now on the RHS. Its turned upside down but all the working of the on/off are exactly the same as when it was GM original. Visually, the underside of the lever is visible but does not detract from the appearance. The grip is normal and the curve of the lever faces the RH door just as it faced the LH door before the switch over.
The Vehicle is an auto. The RHS foot well was widened and is now similar to the RHS to accommodate the pedals and driver's feet. Lights were realigned to the left and tail light lens covers were change to Oz compliance codes. The vehicle was fully inspected and certified to Oz standards by an independent registered auto engineer. Conversion was completed in 2002 and took 3 months. The RHS conversion was completed by a specialised/registered conversion workshop.

 

If you have low fluid flow at the calipers it could be the rubber hoses or the abs. I had very little fluid coming from my rear calipers when bleeding them. I replaced the rubber hoses, but that wasn't my issue. I replaced the abs unit and that solved it.

 

Thanks for the info. I'll give the Ultimates a try. I found the code for the front pads. I assume they also sell the same metal Ultimate for the rear pads. I assume you replaced both front and rear at the same time. Do you know what the pad specs were of the pads you replaced with the Ultimates? Did you do anything modifications additional to changing the pads to Bendix Ultimate? All additional info will be welcome.

 

Thanks. The mechanic did not report any abnormal flows. He flushed the full system and replaced with new fluid so I expect the flow at the wheels is okay.
Where did you buy the new ASB unit and what was the approx. cost? How would you rate the braking now?

 

Thanks for the details I really appreciate it and would love to see pics eventually.

Regarding the ABS, it can fail as an open bypass but it can also fail in a variety of stuck positions which give the brakes a sometimes erratic and unpredictable feel or steadily bad behavior. This is not conjecture but I and many others here are living proof of this. There is no absolute way to "test" the ABS except to bypass it and note the results. The ABS used in this generation was also used in a Mercedes and they have the same exact issue which is as follows: There are no new ones, they are not rebuildable or serviceable, there are no repair parts or anything to repair. When someone says they put a "new" one in it's a used one which at almost 30 years old will eventually lead to the same issues. You can read through the seemingly endless "my brakes suck" threads here and replace parts endlessly, like most. Or definitively determine the ABS's role in your systems issues.

 

Just my $0.02 - but while the C4 brakes aren't quite up to "world class" standards - I tend to think most people are harder on them than they deserve. There were two brake packages offered on the C4, the "base" package had the 12" rotors - the higher performance system had the 13" rotors. The higher performance system is a better system all around - but it won't fit all flavors of C4 wheels.

So - if I were in your shoes - I'd replace the two front flexible hoses, and I'd go with a high coefficient of friction street front brake pad. Over here in the US - that's probably about $120 or so worth of parts, There are a number of brake pad suppliers to look at - just off the top of my head - EBC & Hawk would be options. I'd also think of going to the 13" "Heavy Duty" brakes if you have the 12" system - I believe the only difference on the front brakes is a different caliper mount bracket. I'd look at either of those two options before even considering touching the ABS system.

I've tracked a C4 for years - and can lock up wheels at three digit speeds without too much of a problem if the ABS isn't happy.... .

 

How did you check them? Visually? That doesn't mean anything. A small swelling when pressure is applied can diminish the braking capacity. How old are the rubber hoses? Braided SS might be even better?

 

I'd do the whole kit and be done with it. I have to bleed the entire system anyways. Might as well suck all the fluid out of the reservoir (I'll bet it was never changed and be right most times, at least here in the USA) and pour in fresh fluid and then bleed the hell out of it.

 

Hi redozvette, you didnt copy me did you with that username ?

the ceramic pads are **** in my opinion - they dont like working when they are cold.
I have used ceramic pads a couple of times, but only because I was stupid and didnt learn the first time.
some people like them, but only because they are quiet and dont dust much.
its a pity that race brakes in Melbourne closed down, they used to make some great compounds.

 

Probably a better idea t do them all - I suggested fronts because if he was changine front pads - it would be easy to do those two lines at the same time....

 

Hi all,
You have all given me some good advice and guidance. It's all highly valued and appreciated.

My system is the base with 12" rotors and base calipers. The calipers are the originals. I replaced the 12" rotors with new 12" drilled and slotted as part of the upgrade. I was tempted to go to the 13" and new calipers but decided to stay with the smaller ones, which was not too smart on my part. The system was fully flushed and replaced with new fluid during this recent upgrade. I am reasonably confident of that. I plan to buy new flexible lines front and back and fit these when I return to Oz. The current ones are the 28 year old originals, so they are suspect . The inspection was visual and from what I am being told, that's an ineffective way to check them. I have a new set of hawk pads for the front and back. I purchased them when I bought the ceramics. I have not fitted the Hawks as yet and will do that ASAP. If the Hawks don't work for me, I'll try the Bendix Ultimates.
The info about the ABS is great and good to know. I have not checked the ABS.... that's also on the to-do-list. With a little luck, it will be okay.
Finally, to respond to blackozvette....no, I did not copy. Its something I thought up without outside contribution...but that's not to say I wouldn't have plaijorised if I I had known of yours earlier!!! LOL

 

I would NOT trust a 28 year old condom to help me avoid 18 years of fawking I get for 1 hour fawking I gave much less a 28 year old piece of rubber hose to stop me in an emergency. YMMV