New member here having purchased a beautiful 1998 stock C5 Convertable with-in the past week. The car has 60,000 miles on it. Its white with a black top. Becoming a Corvette owner has been a latent wish I've had for several years. I currently own a another chevy, its a(Avalanche). Anywhos enough with the introduction................
Like I mentioned I just purchased the Corvette and was unfamiliar with the car or any problems it may have had that needed attention. The over-all condition is very good. It did appear that the most recent past owner negleted giving the engine bay any extraordinary TLC. Some thing I am in the regualr habit of with my other vehicles. Nothing major other than a good power cleaning and I had that issue resolved. While driving the car in slower traffic for the 1st time this past week I did notice the temp gauge rising to nearly 230* while iding still. I am not use to seeing this happen in my Avalanche. The temp would drop to about 195* while driving on the open hwyway. The engine nor radiator hadn't shown any signs of leaks on visual inspection. This got me to wondering as to why the engine temp would slowly rise at lower speeds only and if the cooling fans were working properly. I held the hoses to feel for circulation and checked the coolant level and mix and all seemed fine. Checked the cooling fan fuses and all appeared in good order. I did notice that the passenger side fan would come on with the AC turned on. This seemed to artifically cool the engine to nearly 195*. I was not aware at that time, both cooling fans were supposed to come on with the AC or that both actually did or had. It was time to get on the net and find reliable information. That investigative move brings me to the site here for the first time. I'm glad I found it. Theres a wealth of good information provided by very knowledgable good people helping solve issues like these available here. I checked all the threads relating to what appeared at first similar excessive engine heating issues. I also learned that the Corvette's in stock form all operated at higher than normal engine temps or should I say higher than normal for most other vehicles. The one thread post of the most help concerned using a jumper wire in the relay circuit to force both low fans on. I did this so that I could check the cooling fans operation while the engine was off. I'm hard of hearing and this made hearing them tons easier. Both fans worked fine on low speed. I was still at a loss figuring out whether or not the fans were running on high speed, with or with-out the AC on. Further investigative visits to the site here explained in detail the unique switching operation of the C5 cooling fans. I went back and let the car idle in the drive until the engine temp gauge read 226* and the fans came on just as explained. Problem was they weren't cooling the engine down to 195* and the temp stayed in the 210* range consistantly. Once again I knew the water pump was operating. This lead me back to the forums here seeking a bit more information on the engine cooling system problems and related preventive fixes. I was really surprised to read the ones concerning debri clogging the radiator and the AC system and about washing clean the radiator. The only problem was deciding whether or not I would attempt taking apart the parts of the car I needed to in order finding out how just bad mine were clogged. I can tell you I have under taken projects like these with-out fear in the past, but that was nearly twenty five years ago and the vehicle wasn't a Corvette. The back was better then too. I do not have a lift nor even a floor jack for a car sitting as low as a Corvette. I would have to attempt the cleaning from the top down. Which is exactly what I did. No problems at all. I used the shop vac and a air compressor once removing the necessary parts. I did not use water in fear of wetting some important electrical items I am not familar with in the engine bay of a Corvette. I did not remove the cooling system entirely but was able to seperate and dislocate them easily enough so as to get the vaccum head and air gun into the proper areas. Boy was it a real mess in there! The leaves, pine needles and grains of sand had nearly clogged every fin opening in the entire cooling system. I worked the vaccum head from one side to the other, backing the opposite side with heavy cardboard creating a negative air flow until all the debri was loosened. I finished up using the air gun to blow the remaining debri completely out from both sides. Once that I could see through the fins of the radiator from side to side and all the debri was cleaned I put everything back together. It was time to see whether or not I had actually helped my orignal problem. I let the car idle for nearly an hour with the AC off. The engine temp gauge never went over 192* and held steady there and the cooling fans never kicked in. Once that was done I took it for a drive at highway speeds with the AC off, no problems and then into bumper to bumper traffic. The AC was still off and still no problems. My last test was driving home with-out the AC on 20 miles as hard and safely as possible, the temp gauge held at 192*. Once home I parked and let the car idle for about 5minutes and the temp gauge rose to 226* and the cooling fans kicked on into high just as they should have and the temp dropped down to 192*. The fans turned off afterwards just as they should have. I'm pleased. Thanks for sharing all the Information. Dave

 

Welcome to the corvetteforum .....

Glad to see that for a new member you were able to research, and fix, your cooling "issue" without apparent assistance from anyone other than previous posts .....

We LIKE people like you ... no ... we LOVE people like you ....

 

It is a good idea not to hose down a C5 engine. There are way too many connectors and sensors that could be affected. Cleaning with brushes/rags and damp SAFE cleaners is much better.

One issue seen on engines that are frequently hosed/cleaned with water is malfunctioning knock sensors. There are two sensors under the intake manifold (a bear to replace) and there is a TSB (Technical Service Bulletin)to build a "dam" of RTV around them when replacing them to keep water out.

 

Well, a new member that comes in and searches before asking you are the exception, great work! Sounds like you'll do just fine and believe me you will REALLY love owning a Covette, and you stumbled onto one of the , no make that THE, best Corvette site available anywhere! Congratulations on your new purchase, enjoy it, remember the wave, and beware the MOD fever. It strikes us all at some time! Welcome

 

Thanks all! This site is very informative and helpful. As a newbie to Vette sites I can say no other is as active nor complete. Its a credit to the site owners and members> I already have the fever to add a few performance mods in the near future. My Avalanche is highly modded so I understand the attraction to modding fever. Any suggestions on what the best bang for the bucks are and why? What I might expect to gain performance wise from these particular suggestions. The C5 is an auto. Thanks again in advance................Regards Dave

 

Well done sir ! It's amazing how much information is available if you are just willing to search. It's equally amazing how many people would rather just be spoon fed, then teach themselves with a few clicks of the mouse.

Good job...enjoy the car

 

"Any suggestions on what the best bang for the bucks are and why? What I might expect to gain performance wise from these particular suggestions. The C5 is an auto."

Swapping the stock 2.73 diff to a 3.42 will be a very big improvement. ~$1500 for a new one, making a good used one an afforable option.

 

Thanks for info on swapping rear gearing to a lower numbered unit. I'll keep an eye peeled out on the boards for a used unit and other suggestions as we near summer. I also took the post serious in the TECH area concerning the importance of keeping the Mass Air Flow Sensor clean. The 98 I don't believe was ever lucky enough to see that item performed so I under took that today. Bought a can of the CRC MAF Cleaner today and removed the Sensor very carefully and cleaned it with the product. I also incorporated using the tips about using Q-Tip swabs to get into the delicate areas around the screening and body materials. I also figured it the best time of opportunity and cleaned the throttle body inside and out using the CRC Throttle Body Cleaner. I grabbed that too while at the Auto Parts store today. Though subjective at this point as to whether I'll see or notice a 4 hp or so difference at the rear wheels, the darn things were aweful dirty no doubt. The car seems to idle slightly smoother, not that it was terrible before hand. It seems to me the greater improvements are in the accelleration at hwy speeds. I swear I nearly broke the rear wheels loose when ever the car hit passing gear. Though I have been gentle this past week with my driving habits being unfamilar with the car, I had punched the pedal a time or two while passing and hadn't witnessed the hidden power the apparent dirty MAF had under wraps. One more added project was included and that was practicing the same proceedure on my Avalanche after completing it on the Corvette. The Throttle Body wasn't as dirty but the MAF was on the SUT. I had been noticing a slight RPM wobble at the gauge needle these several past months, especially while the engine and air temps were cold on start up. That wobble at the gauge is gone now and the test drive proved quite interesting. The AV has really come back to life...................I'm pleased no doubt and beholding to those of you experenced and caring enough to share the why and hows too's of these easy to accomplish and benefical tasks.. Regards Dave

Oh! I also added a pint of the Seafoam mentioned on the boards to the tank of the Vette today after the test drive..Hope it helps as much too!

 

I will admit I didn't read the entire thread line by line, so you may have already checked, but the RPO plate under the center glovebox lid will have either GU2 or G92 or G90. GU2 is the 2.73 ratio. The others are both listed as 3.15, which is the "performance axle ratio." Here's a URL to get all the RPO codes. http://www.corvetteactioncenter.com/...98/98rpos.html

On my 1999 A4 coupe, the Diablosport Predator did a good job. About the same miles as your car. It dials back the torque management so you get a bit more seat of the pants power. It also programs the fans to come on at a lower temp, and leans the fuel maps a bit. Requires 92 octane to use, but it was a good mod for an old guy. A custom tune would no doubt be better, but with this, I can put it back stock for the biennial Smog Checks here in the People's Republik, and it's enough for me. General consensus is that they have the most benefit for the A4 cars. I added a Vararam to my car, too, which lived up to its advertising.

For better or worse, I've traded that car for a 2002 M6 convertible, and don't drive it nearly as hard as I did the A4 car. Like I said, I'm gettin' old, but I prefer the A4 for drag racing. I can't shift as fast as that automatic. But if you do dial the perf up a bit, have the trans checked, and have a plan B for if you overstress it. The recommendation on the forum is for Rodney at RPM Transmissions.

Enjoy! I would rather have the A4, since it's easier to do the "stab-n-steer" thing with them, but my M6 car had such low miles, and was in like new condition, so I'm switching over to the sports car driver approach instead of the mongo power straight line approach of past years. That old Shelby was heavy, and most of it was on the nose, so the A3 and the 428CJ motor made for a straight line rocket.

Funny thing is, good as that car was when I bought it in 1975, the '99 A4 coupe would no doubt have outrun it in a drag race. I'm sure yours would, too. These cars (recent Corvettes) are just such a great value for the money, and aren't bad to keep up, really. I can do most of the maintenance and many of the repairs. The shop manuals are a real benefit, too. Unfortunately, I have the 1999 set. Fortunately, the changes seem to be minimal. Maybe I'll find someone who wants to swap for a 2002 set one of these days.

All the best to you!