87 prelude runs hot in heavy traffic

Hi,

I am new to this group and this question may have been asked before.

My'87 prelude SI runs great but in heavy stop and go traffic the water
temperature goes way up at 80% and then the fan engages and cools it down to
50% levels. In normal driving it is stable at 30% of the gage.

This has been happening for couple of years and I am wondering what could be
wrong. In the past the hottest the engine got was at the 50%. My mechanic
friend said that it is the fan switch. I had it replaced and the problem
persists.

Is there a thermostat that needs to be replaced? Could it be a sensor
somewhere else that is broken? I just replaced the vacuum next to the
distributor and oxygen sensor during a smog check.

The car has 190,000 miles on the odometer and I have been the sole owner of
the car.

Thanks for your help in advance.

 

Do your radiator, water pump and thermostat also have 190,000 miles on them?

 

When this happened to me, the dealer said I had a blown head gasket
while a local independent mechanic showed me the cracked radiator. If
you have a plastic radiator check for tiny cracks, that would of
course, expand when your engine heats up.

Cow

 

Go with the new thermostat. Since the temp goes down to 50% and fan
still runs, it means thermostate not fully opened.

 

|>My'87 prelude SI runs great but in heavy stop and go traffic the water
|>temperature goes way up at 80% and then the fan engages and cools it down to
|>50% levels. In normal driving it is stable at 30% of the gage.
|>
|>This has been happening for couple of years and I am wondering what could be
|>wrong. In the past the hottest the engine got was at the 50%. My mechanic
|>friend said that it is the fan switch. I had it replaced and the problem
|>persists.
|>
|> Is there a thermostat that needs to be replaced? Could it be a sensor
|>somewhere else that is broken? I just replaced the vacuum next to the
|>distributor and oxygen sensor during a smog check.

First step: Open the radiator cap when it's cool. Is the coolant full to the
brim, or is it down a bit leaving an air space? If it's not completely full,
buy a new cap.
While the cap is off, look at the interior and see if it looks clean or if it
has a coating on it. If so, get a flush and fill kit ($4.99 at most auto
stores) and some radiator flushand a gallon of coolant, and follow directions.
You will have to cut a heater hose for this. If it's an original hose, it
probably needs replacing. This wold be a good time to take care of that. It's
cheap.
If possible, check the space in front of the radiator, but behind the A/C
condenser. There is less than an inch between them, and it can get clogged
with leaves and debris, reducing cooling area considerably. You cannot get it
all out just shooting water through the fins from the engine compartment, but if
that's all you can do, it will help.

I wouldn't think the thermostat is at fault. Those usually fail open (won't
warm up quickly or at all) or closed (pegs the gauge 5 blocks from the house).
Temp semsors - the only one that would affect this is the one that turns on
the fan, and you said that works. It is remotely possible that there is a 2nd
sensor that runs one fan in an intermediate temp range. RTFM on this one.

Hope that helps, good luck.

Rex in Fort Worth

 

This seams to be the best first step. I'll let you know of the results.
Thanks.

 

Oh! where exactly is the thermostat located? I am considering replacing it
myself!

 

I don't know about your engine on my Integra it's down on the bottom of
the block near the water pump, However an old 82 Accord I had it was up
by the cylinder head. If you're going to get into repairing your car
(even small repairs) a genuine Honda Helms manual will go a long way and
be a *great* investment.