Does anyone have any more information on this TSB (88-174-6)? All I've found is "5.0/5.7L-V8: Coolant loss 1987-88 FREE REPAIR (88-174-6)" and I think this may be happening to my 5.7 GTA - I've replaced about 6 hoses now AND the radiator but continues to lose coolant. I hope it's not some inherent defect I'll have to live with on this car - she's grown on me in the last 9 months of owning her.

 

Well for starters i cant say ive ever heard of that survice bullitin. However when they put out a service bullitin it means that the mechanic when makeing repairs will replace the deffective part with a updated or corrected part or make the repair useing a revised method. So for example if GM finds that a hose is deffective there might be a service bullitin about the problem/what caused it and most importantly how to correct it which might be to just use a hose that has a new corrected design. I can say that this isnt a problem youll have to live with there is a fix for whatever is causeing your leak. THe question is where is it? Now if youve replaced the hoses and the radiator ide say its safe to assume thoes arnt the problem. My next question is do you see any coolent leaking? Not just on the motor or on the ground but also check the passenger side floor pan up front inside the car as the heater core could be leaking as well. Do you notice any excessive smoke from the exhaust or under your oil cap theres a film with consistency of a milk shake?

 

I should say that I had 6 hoses and the rad replaced, by 2 mechanics. I've looked at it on my own and did not see any obvious signs of leakage. The 2nd mechanic replaced each hose as a new weak spot was found with each subsequent pressure test, until finally he said the rad developed a leak, so I had to get that replaced too. But a week later, my coolant level keeps dropping at the same rate as before. Therefore it's leaking under load or consuming the coolant. There's none in the oil luckily, but everything points to a leaky intake gasket and after dropping $500 last week on fixing this damn leak, I'm not about to drop more cash in such a short amount of time, especially if it turns out to be a chronic condition on this '88 350.

 

Well i wouldn't be to worried about it being a chronic condition as its just a standard small block chevy which has no problems with water leaks at least no problems out of the normal issues any motor would have to deal with. If anything they probably produced a bad batch or poorly engineered set of gaskets, hoses or whatever that were prone to leaking but something like that would have been corrected in future years with an updated replacement part. Futher more idk if ide trust thoes mechanics if theyve charged you all this money and have replaced hoses/radiator blindly and still not been able to fix the leak. No offence to them but come on a coolent leak isnt that hard to diagnos and bad hoses are obvious even to the untrained eye so how they got off charging you 500 to change hoses and not fix your problem is beond me. First i would run the car to normal operating temperature and carefully do a visual inspection of all the hoses. next try bypassing the heater core to eliminate that as a possability as if its leaking slowly into the interior you may not even notice it and its not like you can really see it and with all the interior pannles it may come out in places you cant see. Now at this point you can guarente that there are no external leaks than it must be internal. If its internal theres only 2 places water can go into the oil or into the combustion chamber. Now if you say theres nothing in the oil which i would double check to make 100% sure as water/antifreeze when mixed with oil and high temperatures and pressures as its run through the system actually forms a weak acid (an acid that eats away at soft mettals like bearings). If you are still confident that its not in the oil then i would try getting one of thoes testing kits that will detect combustion gases in the coolent (can be bought at places like napa and autozone any autoparts stores). What they do is the testing fluid provided will change color when in the presents of coolent that has combustion gases in it. If thats the case it would indicate a bad head gasket or cracked head or block something like that. Also what color antifreeze are you running the green stuff correct?

 

I called the shop and they're gonna take it in to test it again. He did say that after all those pressure tests that the following morning he got white smoke out the tailpipes when he cranked it. So I guess my suspicions are correct?

But like you said, if I can pick up a test kit off the shelf to determine a combustion leak, he sure as hell could've done that while he had the car to remove all doubt instead of releasing the car to me and hoping for the best.

As for the coolant, I had my system flushed a few months back and the guy put some red coolant in the system, so this guy refilled it with dex-cool after testing it.

 

Well for starters if it blows out white smoke on a start that could be oil from leaky valve seals could just be condensed water in the exhaust one of those things its hard to tell without seeing/smelling it. Next As far as if i think the mechanic did as he should no for 2 reasons one if you dropped it off to fix a leak and he has a coolant system pressure tester you can see if a leak is fixed or not and obviously it wasnt and second you don't just replace things blindly you test things that's what separates technicians from parts changers. Also the icing on the cake would be the antifreeze. Although the red stuff should be ok, although ive heard mixed things about it, the dex-cool is junk and GM is being or was sued over it. Apparently complaints ranged from leaking intake manifold gaskets to having the stuff turn into gel causeing overheating. Now when used properly dex-cool can be ok but one of the other problems with dex-cool you cant mix it with anything otherwise it can cause all kinds of problems again rangeing from forming sludge to forming a weak acid. Concidering its virtually impossable to get all the old coolent out ive never heard dexacool being recomended for use unless your car came with dex-cool and is probably a bad choice to use. Further more although Dex-cool is used on new cars that use aluminum radiators and stuff its not ok for use in old copper set up like your current copper radiator/heater core and will eat away at them and they will fail (leak) in a realitivly short period of time depending on how worn they already were and other factors. Personally ide stick with the green stuff the red ive heard mixed things about but also should be fine and have a longer life than the green stuff. So thats a judgement call but no dex-cool.