'86 LX Runs Hot at Idle

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06-07-2010, 10:06 AM
Goody4

'86 LX Runs Hot at Idle

I have a 1986 Accord LX with 78,700 original miles. I recently had the water pump, serpentine belt, and alternator belt replaced. The radiator and A/C compressor are both less than two years old.

My car now runs a little hot at idle. I'd say the needle gets to about halfway between normal and hot when the car is at a standstill.

The mechanic's notes after he changed the water pump said, "Could not replace thermostat, screws seized, would have to replace as a whole unit."

Also, this car idles at 1250 RPM. I'm not sure I want to open this particular Pandora's Box by trying to adjust it. I've heard nightmares about adjusting Honda carburetors.

My questions are:

--Is this hot idle ok the way it is? The temperature does settle down to normal once the car is under way.

--What did the mechanic mean when he said "replace whole unit"? I didn't look at the notes until after I had the car home. Is the whole unit expensive?

--Would changing the thermostat cure this problem? Would adding a little more antifreeze help the needle dip back down to normal when the car is at idle?

Please don't get too technical. I am a mechanical dummy.
06-07-2010, 10:23 AM
stephensimmons

Re: '86 LX Runs Hot at Idle

The thermostate is mounted in the housing that holds the distributer also. and as for your heating problem, it sounds like your cooling fan for the radiator isnt working properly or not at all.
06-07-2010, 12:20 PM
Goody4

Re: '86 LX Runs Hot at Idle

Quote:

Originally Posted by stephensimmons

The thermostate is mounted in the housing that holds the distributer also. and as for your heating problem, it sounds like your cooling fan for the radiator isnt working properly or not at all.

Thanks for the thermostat information. The cooling fan is working, turning on and off, as needed, while the car is at idle.

I don't know the symptoms of a faulty thermostat. For now, I'm going to add add a little a coolant.
06-07-2010, 12:33 PM
stephensimmons

Re: '86 LX Runs Hot at Idle

I might have one of those housings i'll check and see
06-07-2010, 01:15 PM
car6289

Re: '86 LX Runs Hot at Idle

Quote:

Originally Posted by Goody4

Thanks for the thermostat information. The cooling fan is working, turning on and off, as needed, while the car is at idle.

I don't know the symptoms of a faulty thermostat. For now, I'm going to add add a little a coolant.

Thermostat stuck closed needle goes pretty much to "H". Your only source of engine coolant cooling is through the heater core thus to the interior of your car.
Interior temp control to full warm, interior fan on high and windows open. A method I had to use to limp my old 87 3G about 5 miles to home to change thermostat.
Thermostat stuck partially open or full open gives longer engine warm up time and possibly some erratic engine behavior during the warm up process. Full open thermostat the temp needle should climb to some low to mid scale position, needle more toward "H" if thermostat not fully opening.
Thermostat housing is attached to the head just behind the distributor
My temp needle sits midscale (needle horizontal) when engine is warmed up.
06-07-2010, 02:51 PM
russiankid

Re: '86 LX Runs Hot at Idle

Quote:

Originally Posted by stephensimmons

The thermostate is mounted in the housing that holds the distributer also. and as for your heating problem, it sounds like your cooling fan for the radiator isnt working properly or not at all.

Do you mean it mounts to the head? The distributor and thermostat housing both bolt to the head. The thermostat cover bolts are known to seize, and if they snap off you have two options. You either drill and helicoil, or get a new housing. Either way the housing has to come off, and it is not fun to take it off due to the EGR piping in the way. However, it is do-able if you loosen the EGR pipe, but a lot of PB blaster is require plus a pipe wrench.
06-07-2010, 07:29 PM
Dr_Snooz

Re: '86 LX Runs Hot at Idle

It's probably your thermostat. The thermostat "assembly" bolts to the head. There are two pieces. The inlet pipe that holds the thermostat and the cover that keeps it there. When the cover leaks, it corrodes the cover bolts and they seize up. You can try using some PB Blaster to loosen them up, but you are probably still going to break them off.

Just go to the junkyard and pick up a new inlet and cover. Then pick up a new thermostat from the store and replace the whole mess. Be forewarned that the inlet bolts are quite a lot of fun to get to though. You'll learn new ways to swear trying to get it replaced.

The moral of this story is that you should always be scrupulous with cooling system maintenance so you don't get leaks and corrosion.
06-08-2010, 04:44 AM
bryan42688

Re: '86 LX Runs Hot at Idle

are your cooling fan's cracked or damaged in any way?are you running the A/c it is normal for the temp to go up 3/4 of the way when running that also it is ok as long as it dont go any further? are you retaining pressure on your cooling system? these are questions you should ask your self because 3/4 of the way for the stat could be normal espectally if there is a 195 degree thermostet
06-08-2010, 05:11 AM
Goody4

Re: '86 LX Runs Hot at Idle

Quote:

Originally Posted by bryan42688

are your cooling fan's cracked or damaged in any way?are you running the A/c it is normal for the temp to go up 3/4 of the way when running that also it is ok as long as it dont go any further? are you retaining pressure on your cooling system? these are questions you should ask your self because 3/4 of the way for the stat could be normal espectally if there is a 195 degree thermostet

The fan, physically, is in good condition. The car's "hot idle" is the same whether the A/C is on.

Normally, the 3/4 mark wouldn't bother me. But, before the water pump was changed, the needle happily sat at halfway all the time, with the car at a standstill or moving.
06-22-2010, 06:05 PM
Goody4

Re: '86 LX Runs Hot at Idle

I cracked the thermostat housing tightening the bolts back on after I (improperly) replaced the new thermostat. The car was leaking coolant so I figured it just needed tightening. Oops! I guess tightening an off-center thermostat only makes things worse.

So, the housing was replaced. Here's where it gets a little odd. At idle only, the car first ran perfect after this fix--the needle stayed dead-center. However, the needle ran to about 2/3-to-3/4 hot when I was on the go. This lasted about a day, the outside temperature between 88-90 degrees F. Both fans are working well.

Today, the temperature gauge ran right in the middle the whole time, for both idle and running through the gears, the outside temperature in the mid-70s.

I wouldn't figure the outside temperature would have much affect the coolant temperature. I wonder if this is something that "corrected" itself.

Anyway, I think I can live with the car if it runs a little hot, should it happen again.
06-22-2010, 07:01 PM
stephensimmons

Re: '86 LX Runs Hot at Idle

Quote:

Originally Posted by bryan42688

are your cooling fan's cracked or damaged in any way?are you running the A/c it is normal for the temp to go up 3/4 of the way when running that also it is ok as long as it dont go any further? are you retaining pressure on your cooling system? these are questions you should ask your self because 3/4 of the way for the stat could be normal espectally if there is a 195 degree thermostet

He is right. try running a 180 degree thermostat if the temp stays up
06-22-2010, 08:37 PM
Goody4

Re: '86 LX Runs Hot at Idle

Quote:

Originally Posted by stephensimmons

He is right. try running a 180 degree thermostat if the temp stays up

Ok. I'll try that if it becomes a problem again.

Also, even though it was only in the mid-70s today, it rained all day, making for some extremely muggy weather. So, I had the A/C the whole time today because it was so humid out.