1990 Honda Accord Overheating

Hi folks,

My old Honda Accord got overheating trouble recently. Here is my
finding:
1. It got overheating on the local right off freeway or a long drive at
local.
2. The radiator fan start up right after the engine is shutdown. It
fail to start even the temperature gauge goes high and the engine is
running.
3. Didn't pay attention to condenser fan.

My doubts:
1. Radiator fan switch is bad. But it did start after the engine is
shutdown.
2. ECM sensor is bad. But I have no idea what this thing is and where
it is located.

Anyone has similar problem?

Thanks

 

For the record, how old's the thermostat? Is it an OEM
thermostat?

www.autozone.com has a free online manual for your car. The
CRX and Concerto factory service manuals at
http://www.honda.co.uk/car/owner/workshop.html should have
some exact instructions for testing various switches and
sensors.

 

Hello,
I suggest that you change the thermostat and check for any leaks while the
engine is running. You should also buy a repair manual for your Accord.
The manual should help you to locate the parts that you mentioned. If you
have never before changed a thermostat, take the car to a mechanic. If
possible, watch the mechanic in order to learn how to do it.
Jason

 

Short the fan's thermos witch. The fan should come on.
If it doesn't, check the wiring.
If it comes on, leave it shorted and see if the temperature remains
normal. If it does, replace the switch. If it doesn't, there might not
be any coolant running by that switch. That might be caused by a bad
thermostat.

Remco

 

I have some new findings now and I am more confused.
1. For switch B, which is the condense fan switch according to repair
manual. This switch is closer to the front compared with switch A. No
fans come up running with the engine turned on even I short it. With
engine turned off, it automatically turns on the radiator fan
(passenger side) when engine is hot or I short it.
2. For switch A, which is the radiator fan switch. This switch is
closer to the fire wall compared with switch B. With engine turned off,
no fans come up even I short it.
With engine turned on, both fans come up if I short it. With engine and
A/C turned on, both fans turned on or off automatically.

Is it possible that the two fans has been mistakenly switched due to
installation error? I mean the radiator fan should come up when I
shorted with engine on.

Thanks for all replies. The conditions are: the thermostat should be
fine because the upper hose is hot. I just flushed the radiator and
carefully refill with a mixture of water and coolant. And of course,
the radiator is kind of dirty. I also noticed that if both fans comes
up, the temperature gauge goes down really fast.

Any other diagnose ideas?

 

When you say switch A and B, do you mean relay?
As far as I know, the condensor fan does not have a switch, but is
controlled by a signal from the ECM. When that signal is true, both
fans should run. I think there's usually a diode pack that takes care
of making sure both turn on.

When the engine cooland temperature switch (the switch, not the relay)
closes, it closes the contact on the radiator fan relay should close
and the radiator fan should run.
Have you located the coolant switch?

 

Sorry about confusing the issue - forget what I just said.
I found the schematic to your car at autozone.com and it has two
temperature sensors A and B - that must be what you are talking about.

I'd measure the voltage across both switches and see what happens when
the car warms up. They should both go from around 12V(cold) to zero
(hot). If you see 12V but never zero, I'd replace that particular
switch. If you never see 12V, check resistance across the switch. If it
isn't shorted, you may have an issue with that fan control module or
the wiring. If it is shorted, those fans should be on..

Report back with your findings. I'll bookmark the schematic.
Remco

 

The manual is not quite correct. Switch B is simply a secondary fan switch.
It comes on at a higher engine coolant temperature, and its power feed is
controlled by the timer unit.

That switch gets its power from the ignition switch. If the ignition is
off, it won't have power.

Do they come on *before* the engine temperature gauge starts to climb?

The thermostat would be fine if the LOWER hose was hot! This isn't a 1976
Dodge. The thermostat is in the LOWER hose. The LOWER hose will not get hot
until the thermostat opens. And neither will the bottom of the rad.

How even is the temperature of the radiator core with the engine starting
to overheat?

Inside or outside?

 

Hi TeGGeR®,

Thanks for your clarification. So I have to take the timer unit into
consideration when I diagnose the problem. Here is the answer to some
of your question:
1. Do they come on *before* the engine temperature gauge starts to
climb?
A> It definitely come on before the gauge reach the normal operation
temperature. I'll test to see if it come on when it is cold started.
2. Inside or outside?
A> Both Inside and outside, I used a power washer cleaned the outside,
but the inside still looks bad.

Question to you:
Where is the timer unit located or is it the ECM? How is it supposed to
work?

Thanks,
Ivan

 

Hi TeGGeR,

One more answer to your question:
I noticed that both upper and lower hoses are hot. When the engine
starts, the radiator and upper hose get hot a whole lot faster than the
lower hose. I also noticed that the old upper hose get swollen really
big before I replaced it. The new upper hose has the tendency to become
swollen.
Thanks for your analysis.

 

Ohhhh, that's not good... If the upper hose is swollen, then you've got
excessive pressure in there. How old is the rad cap? Have you tried
replacing it?

Sounds like you probably have nothing wrong with your timer unit, but more
mundane problems with a dirty system or bad thermostat.

If you still want to find the timer, it's here:
http://www.tegger.com/hondafaq/misc/89-91_Accord_underdash_relays.pdf

 

The cap is a new one and I am in the process to replace the radiator.
The problem is I rarely saw the coolant flow to the reserve bottle.
Let's suppose that the system is dirty and flow really slow, the
coolant still still need to flow to the bottle if it is really hot.
I'll see if replacing the radiator make any sense or not. I'll post the
result here.

 

excessive pressure in the cooling system could also be a bad cylinder head
gasket.

 

Correct. And at that point you'd see the reservoir level climb up high,
then not drop back down again, and the rad level would decline at the same
time.

 

Replace the thermostat first.

Check my other reply (to Jim Yanik).

 

That doesn't make a lot of sense to me - I would think the cap would still
bypass the pressure - but it is widely reported so somehow it must be true.

Mike

 

I asked a garage to replace the thermostat when they replaced the
broken water pump (I mean it was broken and water leaked out through
the hole). If they really did it, my thermostat is only two months old.
The garage guys just can't figure out the problem and asked me replace
everything except the engine.

 

OEM Honda is recommended. Maybe they put in an aftermarket thermostat?

 

When I checked thermostats at PepBoys,all they had was 180 degF ones,and my
Integra GSR uses a 195 degF TS. I bought one from the Acura dealership.

 

The thermostat they replaced got to be an aftermarket one. The radiator
running in this car is also a aftermarket product. I am thinking to get
all these corrected.