A series of mysterious issues

[Jupiter43]

Hello everyone,

I drive a 1993 Buick Park avenue Ultra with roughly 153,000 miles on it, although it's almost entire in mint running and physical condition, I have a few annoying issues that I can't seem to shake.

First off, and more importantly, I have a very small coolant leak. If I were to fill up my coolant entirely, it would last about 2 weeks before the 'low coolant' light would show. Now, initially my water pump was bad and I replaced it; problem fixed, momentarily. At random the issue sprang up again, but the leak is impossible to find. The first time, coolant would spray up the belts and land onto my coil packs, and yet, now the 'new' coolant leak isn't visible anywhere on the engine compartment. Not sure what to do with this one...

Secondly, My heat and AC are semi to non-functional. My heat BARELY works, it slowly warms up over time, but is never hot. I've been told that my coolant leak has something to do with this issue, if it does, please tell me so. I would hate to have to replace my heater core. My AC doesn't work whatsoever. Now, my compressor uses R-12 (as it's relatively old), which is no longer available to the public unless one has a special license. I've heard of 'substitutes' that work, or I could just go about converting the oil to R-134A (which I'm not too sure on how to go about that).

And thirdly, my vehicle slightly misfires at idle. It is very slight, however about once a month when cutting the wheel to pull out of my driveway it'll stall. Also, in order to start my car I generally have to tap the gas pedal for a mere second while igniting the engine to get a good start, or it may fall victim to immediately stalling. The only time I don't have this issue is when It's extremely cold outside, then it'll start right up. It also seems to slightly misfire if it maintain the exact same speed for a while, so on the highway I take my foot off of the accelerator slightly and then press down again to maintain a 'smooth' ride. Now, I've already replaced the coil packs, spark plugs, and spark wires. Initially upon doing so my vehicle didn't misfire once, and overtime it began present itself once more.

I'm at a loss with these issues, and I could use some serious help. I understand you're all very busy people and I greatly appreciate any help I receive, my car and I thank you greatly.

**EDIT**

I believe my intake manifold is leaking. Upon purchasing the car, when I skimmed through the maintenance receipts, the most recent one was a diagnosis saying that the intake manifold was leaking. This most likely explains my coolant AND misfiring issue. How to do go about fixing this? Can I use anything cheap like quicksteel or form-a-gasket?

 

[HotZ28]

First off, and more importantly, I have a very small coolant leak. If I were to fill up my coolant entirely, it would last about 2 weeks before the 'low coolant' light would show. Now, initially my water pump was bad and I replaced it; problem fixed, momentarily. At random the issue sprang up again, but the leak is impossible to find. The first time, coolant would spray up the belts and land onto my coil packs, and yet, now the 'new' coolant leak isn't visible anywhere on the engine compartment. Not sure what to do with this one...

When you replaced the water pump, did you also replace the coolant bypass fitting & hose??

Secondly, My heat and AC are semi to non-functional. My heat BARELY works, it slowly warms up over time, but is never hot. I've been told that my coolant leak has something to do with this issue, if it does, please tell me so. I would hate to have to replace my heater core. My AC doesn't work whatsoever. Now, my compressor uses R-12 (as it's relatively old), which is no longer available to the public unless one has a special license. I've heard of 'substitutes' that work, or I could just go about converting the oil to R-134A (which I'm not too sure on how to go about that). The engine coolant must be full in the radiator for proper circulation through the heater core. Is that so?

You have an 23-yr old car, which should have already had some new A/C components replaced, like the compressor, accumulator & expansion valve as well as an conversion to R134-a. If the car is nice as you say, it should have proactive maintenance to prevent failures.

And thirdly, my vehicle slightly misfires at idle. It is very slight, however about once a month when cutting the wheel to pull out of my driveway it'll stall. Also, in order to start my car I generally have to tap the gas pedal for a mere second while igniting the engine to get a good start, or it may fall victim to immediately stalling. The only time I don't have this issue is when It's extremely cold outside, then it'll start right up. It also seems to slightly misfire if it maintain the exact same speed for a while, so on the highway I take my foot off of the accelerator slightly and then press down again to maintain a 'smooth' ride. Now, I've already replaced the coil packs, spark plugs, and spark wires. Initially upon doing so my vehicle didn't misfire once, and overtime it began present itself once more.

In addition to a coolant leak, you may have a bad or corroded connection on the ICM, PCM or the battery connections may not be clean & tight.

I believe my intake manifold is leaking. Upon purchasing the car, when I skimmed through the maintenance receipts, the most recent one was a diagnosis saying that the intake manifold was leaking. This most likely explains my coolant AND misfiring issue. How to do go about fixing this? Can I use anything cheap like quicksteel or form-a-gasket?

Leak sealer will clog the radiator & heater core! Do not put any leak sealer in the coolant system, replace the gaskets.

 

[Jupiter43]

I did not replace any of the hoses when doing the water pump, I should probably go back and do those....

However, I'm almost certain that my coolant leak is now internal, and that my intake manifold is leaking. Which would also explain my misfiring problem. Now I'm not sure if the leak is coming from the upper or lower portion of the intake, however, the coolant flows through the upper manifold to my knowledge, so I suspect it's that portion. I also have the Supercharged version of this vehicle, meaning that those gaskets differ from the standard 3800 parts. To my knowledge my supercharger is de facto my actual upper intake manifold within itself. I have no idea how to go about replacing this part... and either a link or a step by step would be very, very helpful.

My AC system was not converted, as my freon ports do not fit the R-134A bottle connections.

My main concern as of now is that damn upper intake...

 

[HotZ28]

Now I'm not sure if the leak is coming from the upper or lower portion of the intake, however, the coolant flows through the upper manifold to my knowledge, so I suspect it's that portion

Are you loosing coolant? If you have an '93 S/C engine, the UIM & LIM are both aluminum, which do not have the same problems as the plastic UIM/LIM. You could very well have leaking LIM gaskets, or T/B gasket, but not the UIM itself. Have you noticed any milky substance in the valve cover area, or oil cap?

My AC system was not converted, as my freon ports do not fit the R-134A bottle connections.

Adapters are available at any part store, to convert the high/low side ports to 134a. You should consult with a professional A/C technician before attempting that conversion. The system must be evacuated, flushed of existing oil, then evacuated again and adding the proper amount of recommended oil! Usually, on this old of an car, the expansion valve accumulator and compressor should be replaced at the same time.

 

[Jupiter43]

I am indeed loosing coolant, but at a very slow rate. Not visible on the engine, so it must be internal.

I'm getting both the upper and lower manifold gaskets tomorrow, I have a few questions about the installation process if anybody is willing to give me a hand.

So I assume I'll have to drain the coolant before the repair, where on the radiator is the release located for drainage?

Also, do I have to flush the oil or no?

And lastly, does the supercharger have its' own oil? If so, will it drain upon its' removal from the engine? And where could I purchase more, and what type?

Thank you so much for the help so far, I appreciate every bit of it

**EDIT**

Also, probably going to sound stupid, but what is a T/P gasket? I've only worked on old Mercedes diesels, and I know those simple, industructible engines like the bank of my hand. But this is the first gas engine I've done work on, and I'm unfimiliar with a lot of it...

 

[Spriteman]

T/B = throttle body gasket

I'm going to leave the SC question to HotZ28 since that's his area of expertise.

 

[HotZ28]

Just a thought about the coolant leak, Have you checked the radiator plastic tank on the drivers side top near where the upper radiator hose connects? It is quite common for these plastic tanks to develop a hair-line crack in that area and it is very hard to see. Usually, it will not leak until the engine has been up to full operating temperature, then when cooling down it will show signs of coolant on the outside. The heat from the tank will dry the coolant, so you may not see it the next day. Look for any visible sign of coolant traces draining on the outside of the tank.

The radiator drain spout is located on the drivers side bottom, of the plastic tank mentioned above.

If the engine oil is not contaminated with coolant, you would not have to flush/change the oil after the repair. You will have to be the judge & jury on that.

The S/C oil will not leak when the S/C is removed, but while you have it off, that would be a good time to drain the oil and refill with new oil. The fill plug is located on the snout and there is not a drain plug. You will need two 4-oz bottles of oil. IIRC, the Eaton M-62 S/C will require about 6-oz of oil to refill (up to the bottom of the fill opening) after a complete drain of the old oil. You can get the ACDelco oil from almost any GM dealer, but it will cost more than ZZP. DO NOT use any other type of oil!! http://zzperformance.com/3800/superchargers-eaton-parts/gm-supercharger-oil.html

The pic attached is of an Eaton M90, but the M62 fill plug is located in the same area.

 

[Jupiter43]

The plastic coolant tank is just fine, I actually pulled it out myself and washed and cleaned the whole thing; however I do have a nice neat new clean one to put in once I tackle the intake.

Thank you so much for the supercharger information, that was my biggest concern, as I didn't want to ruin anything when taking it off.

Also, I fixed my misfiring issue ALMOST entirely. When I tuned up the engine I was an idiot and threw in Bosch Platinum +4's, not realizing the negative effect with that engine solely because the spark plug compatible book said it was compatible... Today I threw in all new AC Delco copper spark plugs, gapped at 0.06, and she's running better than ever! Unbelievably smooth ride, noticeable increase in acceleration/HP, no misfiring during acceleration, and barely any misfiring at idle. I believe the very slight and almost unnoticeable misfiring at idle is due to the intake leak... but I'll cross that bridge when I come to it.

I'll check the oil carefully tomorrow, she's due for an oil change anyway, it's been just about 3,000 miles. I have noticed that many of my coolant and radiator tubes are very old and worn, although no noticeable leaks as of yet...

Another odd question, I've heard of the terrible reputation of the godforsaken Dex-Cool coolant (many here refer to it as Death-cool 😎 ), and since my ownership of the vehicle I've been putting in the green Napa brand coolant compatible for all GM makes 1995 and earlier. Is this the best option for my car? I've seen the yellow colored coolant, which states it's safe for all makes and models, and I'm sure I read somewhere of somebody using it in place of Dex-Cool, but I just want to know if it's better, or safe, to use than the standard green I use now.

Would you or anyone here happen to have a picture showing the location of the lower intake gasket? I believe that one is on the side of the engine, although knowing the exact location and which accessories I'll have to remove would be amazing. Naturally when I tackle the S/C gasket I'll have to remove the alternator, and P/S pump *sigh*

Honestly thank you both so much for your time, commitment, and aid during this long and painful process, and to anyone else who pitches in, I thank you as well. I know I probably sound unbelievably inexperienced, to the point where I must seem like an 80 year old man who's never worked on a car before haha. I'm only 20 and my only mechanical experience is backyard knowledge. my previous two cars were a 1985 Mercedes 300TD and a 1982 Mercedes 240D, the amount of work and research I did on those allowed me to understand those indestructible engines upside and down, so I apologize for my cluelessness

 

[mikec6201]

Jupiter , I believe he meant for you to check the radiator . It has plastic tanks on it instead of copper like they used to have . The plastic on the radiator can crack and leak . Also DO NOT mix different kinds of coolant ! If you switch to the regular green coolant you must do a complete flush to get rid of the other stuff . Otherwise you will end up with sludge .