Who is a good mechanic for trouble shooting a overheating 91 accord

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Quest

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Check your radiator fan's relay. Also check/replace your radiator cooling fan thermoswitch.

Have someone test/verify that the fan unit is getting the "juice" when it hits the temperature range so that the fan should kick in. If not, most likely you have a fusible link/fuse problem (check your fuse box for master radiator fan fuse to see if it's burnt).

retest the fan and other electrical components if in doubt.

This is not as perplexing as you think (on a Japanese car that is). Try diagnosing something similar on a 91 Mustang 2.3L and you'll be into something really interesting....*grin*
 
I believe the cooling systems in that year Accord have an air bleed valve to remove air from the system after you do a drain and refill. You may want to check that too.
 
quote:
Originally posted by Quest:
Try diagnosing something similar on a 91 Mustang 2.3L and you'll be into something really interesting....*grin*
Click to expand...
I've diagnosed several electrical/emissions related problems with my 1988 Mustang 5.0. No problem. I do have the appropriate reference materials (wiring diagram and powertrain control/emissions diagnostic (PCED) manual, although the PCED is for a 1992 Mustang).

I assume that the 91 Mustang 2.3L is using an EEC-controlled cooling fan. Diagnosing that without the reference materials WILL be an excercise in parts-swapping and futility, just like diagnosing the oxygen sensor lean code in my 1988 Mustang would have been.
 
Check into what 427 has to say. After that, get a scantool and see exactly what the coolent temp is as the guage/sender may be screwed. Half way up the gauge sounds about right. Maybe your thermostat has been stuck open all along and now it's running where it should be!
 
I don't think there are any aftermarket scantools which will tell you what the coolant temp is on a 1991 Accord. You could check for a temperature/voltage chart in the shop manual and measure the voltage across the temperature sensor.
 
it's not so much where the gage is, it's has it changed from whatever normal is. In most cars, halfway is pretty normal, altho, fwiw.

Most of the suggestions here are what I would check.

moving up with speed pretty much leaves out the fan/relay/circuit as the causeof the problem in most cases. I know you've already replaced it, but the problem as you describe it really does sound like a t-stat. Honda t-stat's aren't really easy to service, they can go in backwards quite easily which would definitely cause the problem.
 
Halfway up the gauge is where my 1991 Accord and my friend's 1990 Accord normally operates when warmed up. I replaced her thermostat when her car would only heat up on the freeway - it was stuck open. If the gauge warms up to halfway and stays there, and the fans operate as they should, then I would guess that you had a malfunctioning gauge sensor and/or thermostat that you replaced, assuming that the original coolant mix was correct.

Take a look at the owner's manual to verify where the overheating range on the gauge is. I think your car may be operating in the range where it is supposed to.
 
I would have to a agree with darryld13.
I think that if it is near the halfway mark it should be OK.
Heck buy a cheap gauge to test and verify, cheaper than throwing money at the car.
Sometimes it hard to let go of the idea that it does not run at the same temp reading. But maybe it was running too cool before.

Good luck on your mission.......
 
OK, I have asked just about everyone I know, here is the question that I would really like to get solved.
4 weeks ago, my 91 honda accord started over heating. I started off by letting it Idle to see if it would get hot, and no such luck. It only gets hot on the highway at about 70+ mph. I found out that my radiator fan is supposed to come on at 189 degrees. The fan never come on, although the fan is operational. The condensor fan comes on at 218, and it does run. So I replaced every sensor that had to do with the fans and the cooling system, there are 4 in all. After replacing all of the sensors, the same problem existed. So I figured I would change the thermostat out and flush the system real good with some super radiator flush. Did all of this and put in a 180 thermostat and some water wetter. Same problem still exists. So I developed a leak this past weekend. I found the leak and drained the coolant decided to take the radiator out and look it over, it was shot and it was missing 30% of its heat transfer fins. So I replaced the leaking hose and the radiator. Today going to work, I was doing 70+ and the needle went up to the halfway region on the gage, it has never run this hot before on the highway since I bought it 4 years ago. So now I am lost and don't know where to go. I changed the water pump out about 15000 miles ago, I sprayed water through the upper radiator hose letting it drain out the lower until the water was clear before I put the radiator in. I am running Penzoil Syn. oil 10-30. I don't think I have a blown head gasket as the car runs too good and I haven't smelled a sweet smell from the exhaust yet. What else can I check? Thanks
 
No halfway isn't, but I have had the car for 60,000 miles and a 1/4 of the way is where it has operated since I bought it and I have replaced the thermostat once. So anything above is questionable when that is all you have known. How would I install a cheap temp gage? It is a 2 prong gage?
 
The temperature gauge is not a precision measuring instrument..so I would verify what it is saying before concluding that the engine is running hotter than it used to be.

I wonder if you could use one of those infrared pyrometers to read the engine temperature? Maybe by pointing it at the bypass hose??
 
the problem with any pyrometer is that unless you are reading the EXACT location and the medium/material that the sensor is reading, you aren't apples to apples.

Engines are designed to run at specific temsp at a particular location, and sensors are located at that spot. It will very likely be much hotter or much cooler elsewhere, especially on the exterior metal surfaces. The sensor is reading the temp of the liquid inside the engine/what/where ever, it's gonna be tough to read that with a pyrometer.

inside every complex problem is a simple solution waiting for someone to trip over it...
 
quote:
Originally posted by kenw:
Engines are designed to run at specific temsp at a particular location, and sensors are located at that spot.
Click to expand...
Yes..but..in the case of one engine, there are 3 sensors, one drives the gauges, one for the PCM, and one for the engine cooling fan (a thermoswitch) and they are all located in different places: For the gauges, in the lower intake manifold, for the PCM, in the coolant tube above the right cylinder head, and for the cooling fan, in the thermostat housing.

I think that this is done because coolant circulation would result in each of those locations reading close (a few degrees difference isn't going to matter, either for diagnosis or for the operation of these sensors) to the same temperature.

In the case of this engine, a pyrometer could be pointed at the coolant tube above the right cylinder head and a reading there ought to be be pretty close to what the PCM sensor is reading.
 
Why don't you remove the thermostat and see if the problem still exists?

I hope you are using distilled water and not tap or well water. I made the mistake of flushing my system with well water years ago, when I was at my uncle's house. After finishing the job and heading home, it only took 3 minutes for the car to overheat. The temperature guage went much higher than it had ever gone before. I suspect, because of the age of your car, you need to install a lower temperature thermostat. Your cooling system may have deteriorated, due to internal corrossion.
 
greasemonkey, i have never heard of a cooling system overheating because well water LOL.. in the past, ive flushed many a car with well water, hose water, etc. with nary a problem..
 
i guess it depends on what is in the well, but if it choked a radiator in 3 minutes I would hate to see my innards....is your uncle still around? (calcium/limestone is very common in well water in Texas et al, so I'm just jerking your chain here, Tx, but it does seem a bit extreme.)

removing a t-stat was a plan on old iron block units, it served well on my 70 cutlass 350 until i replaced the fan clutch (fixin' that ol' root cause again).

But it's not really a good idea on smaller aluminum blocks. Often the t-stat housing uses the t-stat as part of the seal, leaving out the t-stat makes it impossible to seal. Not sure on Honda, tho.

[ July 27, 2005, 03:08 PM: Message edited by: kenw ]
 
Well water was from Davie, FL, which is very high in calcium and phosphate. My uncle, a great Purdue engineer and Annapolis graduate, died March 7, 2004. He was the only officer who survived the U.S.S. Southern Seas going down off of Okinawa in WWII. He was my mentor, instrumental in inspiring me to go to aerospace engineering school, and swore me in as a 2LT in the Air Force. As an R&D supervisor, he developed a number of the weapon systems used in the Gulf War and in Operation Iraqi Freedom. He was a great American.

Back to the thread, I can take the thermostat out of my Honda and it will still seal. You would only do this temporarily to help you isolate the problem. Otherwise, your gas mileage would be shot, performance would suffer, and you wouldn't have heat in the winter.
 
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