Remove and Clean your Radiator
by Lars Grimsrud
Musclecar, Collector & Exotic Auto Repair &
Rev. B 6-19-00
This tech paper will discuss the removal,
exterior cleaning, and installation of the radiator on a 1985 L98 C4
Corvette. Other years are very similar in procedure, and utilize the same
C4 Corvettes seem to have
chronic overheating/run hot problems, especially after about 100,000
The radiator on a C4 ‘Vette is an aluminum and
plastic, single-row unit. It is remarkably small and light, and looking
at it, you just know that it can’t possibly be big enough to handle
the cooling for a high performance, V8 engine…
The design of
this compact radiator is right out of state-of-the-art NASCAR radiator
designs: Every single little fin in the radiator is a multi-piece,
serrated fin – not a solid fin like on the old “heavy duty
4-row” radiators in our old Musclecars. This makes the ‘Vette
radiator highly efficient, and allows the use of a very small
But this small, efficient design is also extremely
sensitive to anything that changes its efficiency. Anything that slightly
reduces airflow, or which restricts the frontal surface area, will
dramatically reduce its cooling ability, causing your ‘Vette to run
hot. You can change the thermostat, flush the cooling system, change your
“fan-on” settings, replace your waterpump, and tear your hair
out, and your ‘Vette will still run hot if the radiator has this
one, eensie, weensie little problem….
The radiator in your C4
is shrouded together with the A/C condenser. The Condenser is in the
front (clearly visible from the front, underneath side of the car), and
the Radiator is in back. Only the back surface of your radiator is
visible or accessible – there is no access, even visually, to the
front surface of your radiator. The plenum that is created between the
condenser and the radiator is a low-velocity air flow area. This area
will become the resting place for every single dead leaf, hot dog wrapper,
grass, and hairy varmint that your car has ever made contact with. How
all this stuff gets in there is one of those mysteries that nobody can
explain. After 100,000-or-so miles, the front surface of your radiator
will be packed with grass, leaves, oil, dirt, grime, rodent hair and other
things that I have yet to be able to identify. You can blow a garden hose
through from the back side, but it will not clear out the front surface of
your radiator, and you do not know that it has happened (since you cannot
If you want your 100,000-mile (and often less)
‘Vette to run 20 degrees cooler, you have to pull the radiator and
clean all this garbage out of the plenum and out of the front surface of
the radiator. This should be a mandatory service process for every
high-mileage, hot-running C4.
Tools and Equipment
As a minimum, you will need the following tools:
Long & short flatbladed screwdrivers. One really small one.
socket with long extensions and a 3/8″ drive ratchet
3/8″ drive socket
4. 7mm socket with �” drive ratchet and
5. 9/16″ Flare Nut (“Lion”) wrench
Soft, long-haired, nylon brush
8. Dish Soap or K&N
Air Filter Cleaner
Pulling the radiator on a C4 is
remarkably simple. Nothing at all like the C3 boys have to go through.
You can do this in about 15 minutes:
� Drain the radiator. I do
this simply by pulling the lower radiator hose off at the radiator.
Pull the upper radiator hose off at the radiator.
� Remove the
overflow hose from the radiator.
� Remove your Mass Airflow Sensor
(MAF) with its duct. Be careful disconnecting the electrical connector so
as not to damage the wires or the connector.
� Remove your air
cleaner and the air cleaner plenum from the top of the radiator shroud.
The two plastic hand-nuts that hold the plenum to the shroud will often
times not come off. This is because the studs on the back side are
spinning. You can keep the studs from spinning by jamming a screwdriver
between the plenum and the shroud, up against the studs. To fix this,
here is a tech tip I received from “LWesthaver” (Wes) on the
CorvetteForum: “Lars, I just faced this problem last week. Since I
had never seen the underside of my plenum I didn\’t know how it was
attached to the shroud. Finally, after figuring out how to remove the
thing, I started looking for a fix. I ended up drilling a 1/8\” hole
through the studs’ metal tangs and the shroud. Once the studs were
re-installed into the shroud’s key-hole opening, I pop-riveted the
tangs to the shroud. No more spinning studs! And it even looks like
something the factory might have done.” Great tip, Wes.
� Remove the 2 10mm screws that attach the A/C
receiver/drier bottle to the frame crossover.
� Remove the 2 10mm
screws that attach the A/C receiver/drier bottle to the fan shroud (using
your long extensions).
� On some years, you may need to remove 2
10mm screws and loosen a 3rd 10mm screw attaching the Power Steering
Reservoir and rotate the reservoir out of the way.
� Remove the rest of
the 10mm screws attaching the upper fan shroud to the lower fan
� Remove the 7mm screws running along the front edge of the
� Remove the upper & lower transmission cooling
lines using your flare nut wrench. Place a drain pan under the area to
catch the few drips that will be lost (you won’t loose much
� Remove the bolts attaching the fan assembly to the upper
� Remove the upper shroud.
� Carefully pull the
radiator straight up, taking care not the bump the fin surfaces against
the cooling fan assembly or anything else.
� Take a look at all the
debris inside the plenum and all the crap on the front surface of your
radiator. Be aghast.
The first thing you want to do is to scoop
all the garbage out of the plenum. Once you’ve scooped it out with
your hands, take a garden hose and blow it out good.
needs some care. The fins are EXTREMELY fragile – much more so than
on the old type of radiators. First, lay your radiator face down on the
ground and blast the big chunks out of it with your garden hose. Now,
pick the debris out of it that didn’t get blasted out by the
Next, spray the entire face of the radiator down good with
K&N Filter Cleaner, or dilute some dish soap into a spray bottle and douse
the radiator down good. The front face is most likely covered in grease,
grime, and unidentifiable road dirt. Taking EXTREME care, gently brush the
front face of the radiator with your soft nylon brush. DO NOT brush from
side to side; brush only up and down (you know – like the dentist
told you to brush your teeth when you were a kid). If you brush from side
to side, even with your soft brush, you will fold the fins right over.
Once you have brushed the cleaner or soapy solution into the front face,
removing all of the oily, greasy crap and build-up, blast the entire unit
off really good with the garden hose again.
Next, sit down on your
front steps with a cooler full of beer beside you, place the radiator on
your lap, and straighten every one of the bent, folded-over, damaged fins
on both sides of the radiator using a very small, flat bladed screwdriver.
If you have a lot of damaged fins, this will take some time, but
it’s the only way to get your radiator up to its intended level of
Once you have cleaned and repaired your radiator in
this manner, install it back in the car by reversing the above steps.
Fill it up with new antifreeze, check your transmission fluid level, and
enjoy a ‘Vette that will often run as much as 20 degrees cooler than
it did before.
Questions, Comments & Technical Assistance
you have questions or comments regarding this article, or if you notice
any errors that need to be corrected (which is quite possible since
I’m writing this from memory…), please feel free to drop me an
e-mail. Also, if you need any technical assistance or advice regarding
this process, or other maintenance issues, feel free to contact