I have a 1991 L98 that I had rebuilt to a 383 stroker w/Lingenfelter super ram. As usual, It runs very hot In the summer with the a/c on when sitting/moving slow In city traffic. It gets to the point where I'm almost at 260 degree In the red zone. I then have to shut off the a/c to bring the temp down just a little. Once traffic picks up, the temp Is fine at 190 to 200 degree.
I have a 160 therm., 2 bottles of water wetter in the radiator, have had the front of the radiator cleaned several times, Have cloth header wrap on headers to reduce engine compartment temp. and had the radiator flushed with It still Installed on my car.
It's a 1991 with 71000 miles on the radiator. Do I just need a new radiator or does the 383 stroker make too much heat.
Thanks

 

It shouldnt be running quite that hot, assuming the WP is good then you need a bigger radiator.

 

A water pump doesn't get less efficient with age like an electric fuel pump. As long as it turns, doesn't make noise, and doesn't leak, it's as good as new.

The thermostat isn't helping anything. Although it doesn't hurt, either. Was the radiator cleaned out from between it and the condenser? This is best done by removing the rad. Does the digital read out agree with the gauge, if you have both? Otherwise, have you verified that it is really that hot? If the cooling system hasn't been well maintained over the years the radiator COULD be partially blocked. Before replacing it, you could pull it and have a radiator shop do a flow test. My '84 has the original radiator core, and it works very well. The only other item, which wasn't addressed, is the fans. Are they coming on at the appropriate temps?

RACE ON!!!

 

Fans are coming on because I have checked them when the engine Is warm and when the temp gets very high.
I also have a breathless perf. vortech ram air Induction. Could that disrupt air flow to the radiator?

 

Are you sure about that? I had a water pump, was still turning, not making noise, and hadn't yet sprung a leak (though it probably was about to- 50k miles on it).

Well, long story short, when I took the car in to be detailed, they killed the optispark, and I had it changed out. The dealer said "Your water pump should probably be replaced as preventative maintenance". So, I did it.

My car ran ~ 20 deg cooler with the new pump.

Now, with my Mez pump, I have the opposite problem- in the spring/winter, I cant get the water temp over 165-170, and in the summer, it barely goes past 180. Guess that 160 therm was a little bit much??

 

My stock '91 did/does the same thing. Stop-and-go is a killer as far as temp goes. I took it to a dealer and he checked the temp and it was lower than the guage indicated. At this point, I just hope traffic starts to move before she blows!!! On a serious note, I think the guage is off. The fans come on at the right time and the car does not smell hot and the oil temp is normal.

 

My 89 vette made it to 251 deg. 2 days ago on the way home from the beach.
I felt the fan temp. and it was not all that hot so I replaced the thermostat with a 180 deg stat.
I boiled it first and sure enough it opened at 180.
the one I took out only slightly opened at about 230.

 

You don't mention what your water/anti-freeze ratio is. Antifreeze is great stuff, but it doesn't cool as well as water. Instead of the generally recommended 50/50 ratio, you might consider a ratio with more water and less anti-freeze to the point where you are still protected from freezing based upon your driving area. i.e. you don't need freeze protection down to -32F in the summer.

You do mention having had the front of the radiator cleaned several times, but that is not the same as pulling the radiator and washing the fins clean of road grime. If you remove the radiator and scrub all of the fins from both sides with a simple green and water mix using a SOFT brush you might se a big difference. Imagine if you never washed your car's paint. How dirty and grimey do you think it would get after a few years? Well, that type of grime can build up on the fins too. Clean them completely and remove any grimey insulating layer. Also, use a small flat bladed screwdriver to carefully straighten every bent fin. The C4 doesn't have an oversize radiator as it is, and with a 383 you want every fin possible working for you.

If you pull the radiator to do a thorough cleaning, I'd follow CFI's advice and have it cheked for internal blockage at the same time.

 

WPs can fail without springing leaks and can still be turning, a bad pump can cavitate more and although it appears to spin fine, there is usually a slight wobble that you wouldnt pick up.

A new pump will cool better than one with alot of miles on it. Seen it several times myself.

 

It does, and it can raise temps 10-20F above where they should be.

 

First, I used a poor choice of words when I said, "it's as good as new". What I SHOULD have said, is that it will pump as good as new. All water pumps will wear out and fail, eventually. Especially with an opti, I understand the "preventative maintenance" aspect, as well as the duplication of labor. If the pump turns and the belt isn't slipping (non LTx engines), the impeller moves water the same as new, until it dies. If the bearings are loose enough to change the relationship between the impeller and the housing, which could affect pumping performance, the pump is on the edge of total failure. In the "olden days", of water pump mounted fans, if we didn't spot the water leak before the bearing seized, the fan got launched through the radiator when the shaft broke.Your car ran 20* cooler? Is it possible they flushed the cooling system? Changed the coolant? Anybody changing a water pump should be shot, if they don't. Could they have cleaned the radiator? The point is, *I* can see no reason why a new, replacement pump, can possibly run cooler that a functioning older pump. I am open to explanations.

The Meziere is a different story. As with any non-stock pump, it has a different impeller, a different housing, and runs at a different speed. I am not saying that different pumps don't perform differently, what I am saying is that a mechanically driven pump doesn't deteriorate in efficiency over time.

RACE ON!!!

 

Since it's with the a/c on, you might want to have your system pressures read (to verify that the high side isn't restricted) and to make sure that the pressure switch is commanding both fans to come on whenever the high side goes over 150 psi. If you have a scanner, you can check the pressure switch reading; otherwise you need to hookup a manifold gage set to the a/c system. You should also make sure that there is nothing blocking air flow between the condensor and the radiator. If it's restricted, pressures will be too high and this will exacerbate cooling problems. Finally, verify that the coolant temp sensor and the gage are within 5 degrees of each other. If not, you may just need a new sending unit for the gage.

 

CFI-EFI-

They may very well have changed out the coolant when they changed the water pump. I am not sure, as this was before I was doing my own work on my car.

However, I do know they didn't touch the radiator. I had noticed that I had a bit of a birds nest in there shortly before the opti and water pump were replaced. I thought this might have been what was causing me to run hot (230-240). However, after they changed out the water pump, it was running 210-220 (weather was about the same) but the "birds nest" was still between the radiator and radiator shroud.

If I remember correctly, the reason for replacing the pump was that the bearings were on their way out. I hadn't noticed any nosies coming from the pump before that.

As for the Mez pump- I do realize it is a WHOLE different ball game. Just need to get the car to run a little warmer (~185-195F for my oil temp, isn't high enough IMHO.. I'm shooting for 200-210).

 

And likely flushed the cooling system, too. If the prior maintenance of the cooling system had been neglected, that could easily explain the car running cooler, afterward.

If it wasn't making noise, I'm curious how they determined that the bearings were bad. Maybe they were just trying to defer some of the costs of a "free" opti replacement? Or did they only charge you the cost of the pump?

I would still like to be enlightened, logically, on how a mechanically driven water pump loses performance with age. I can't see it, but I'll be happy to listen.


I think the stock stat for your car is a 180*. That should help.

RACE ON!!!

 

I have only 1 gallon of antifreeze in the radiator, the rest is water + water wetter (2 bottles)
WP was replaced 2 years ago.
I've noticed that the a/c clutch is engaged even when the a/c is shut off.
What the hell is going on???

 

Is the defroster on? That runs the compressor.

RACE ON!!!

 

Well, it wasnt costing them anything to replace the opti- they wre getting paid for the job, by the detailling company that hosed my opti. It was probably one of those "best to replace the WP while we are in there", and yes, they only charged me the cost of the pump, as the labor was already being paid for in the opti swap.

I can see how this might happen, if there was something mechanically changed with the impeller. If there was some sort of buildup on the blades, or somehow a blad ended up bent (dont know how this would happen, but there are a lot of things that have happened on my engine that I cant explain ). But, if the impeller lost the angle of "attack" due to either buildup or a bent impeller blade, you could end up with cavitation, which would greatly reduce the flow of the pump. It is actually pretty startling how small a change in a blade can cause cavitation.

Another possibility, if the bearings were going, is that there was a small wobble in the impeller. Even a wobble small enough not to be heard to the untrained (my) ear, could also cause cavitation, and reduce flow by quite a bit.

 

defroster Is off