need help w/ my '91 Riviera

[Guest]

Have a '91 Buick Riv. Replaced old a/c system with newer one and now my car overheats. Re-wired the high-speed fan to run continuously and car is still over-heating but not as quick as before the re-wiring. I'm at a loss at what the current problem could be. can any one help who has knowledge.

Thanks,

Jack

[86 2dr.ltd]

The problem shouldnt have anything to do with new system unless you changed the condensor to one that restricts air flow to radiator. I'd change the thermostate first. Then blow out the air passages through the condensor and radiator. Then think about new radiator . Hot wireing the fan is just a bandade and should never be necessary.

[NTX5467]

I concur, direct wiring the fan should not be necessary. Modern radiators are very efficient when they are clean inside and out.

The new condensor might be restricting some air if it has a higher fin count/inch than the previous one did, but I don't suspect that would be a major issue. What might be an issue is if some of the rubber baffling that might have been sealing the condensor off to the surrounding underhood areas was not replaced as it was old and crumbled. Similar if there now are air gaps around the edge of the radiator too, that weren't there previously, which will allow air to go around the radiator instead of through it.

Check the baffling and air dam under the front bumper area to see that everything that was there when the car was new is still there and attached properly. If there was something there that would help route the incoming air to the condensor/radiataor assembly that isn't there now, running the fan constantly on high speed might be compensating somewhat, but not completely.

Finally, although a cross flow radiator might appear to be good when you look down through the filler cap neck, it can be seriously clogged in the lower passages and cause what you are experiencing, especially if the new condensor is more efficient than the older one at shedding heat from the refrigerant. The composite aluminum radiator is an extremely efficient item so replacing it with a copper one isn't a good option for many reasons, nor is running a lower than stock temperature thermostat.

I suspect that ultimately you'll end up with a new radiator in there. Then you can make sure all of the baffling is in place and can get the fans wired back in as they should be. Don't forget to use the correct amount of regular coolant in the system too.

Just some thoughts,

NTX5467

[Guest brh]

Vote number 3 for a radiator problem. My car was overheating (has no a.c.). Took the radiator to a shop to find it was 30% blocked, yet when I replaced everything it looked like coolant was moving through the system. Moral of the story, have the raditor flow checked, if you have an aluminum one it will probably be cheaper just to replace.

[Guest]

Thanks for the advice! I'll show this to my mechanic and hopefully we can figure this out.

Thanks,

Jack

[Barney Eaton]

For some reason the 3800 thermostats tend to go bad. I have had several (190 degree) that don't open until over 200. Clean the radiator if you think it is the problem but replace that $5.00 thermostat.

[NTX5467]

With respect to 3.8L thermostats, there was a service bulletin in the later '80s dealing with temperature gauge "overshoots" as the thermostat initially opened. Seems the temp gauge would head past the point of opening and then suddenly fall back to where it should have been as the thermostat did it's "thing". The bulletin mentioned the existence of a small hole in the thermostat's flange as being necessary for a little more "bleed through" of coolant during this transitionary period. Later versions had the bleed hole with a loosely fitting small rod in the hole for something of a variable orifice situation.

Be aware also that the temperature rating of the thermostat is the openning temperature and not tne "full open" temperature. That's the way I've seen it explained in some service literature.

Hope this might help,

NTX5467