Overheating Issues - Accord Coupe EXL V6

[Che]

I have an Accord Coupe EX V6 with over 215K miles. About 1 year ago (July '08), I noticed some temperature excursion issues. While driving on the expressway, the temperature gauge would show normal (less than halfway mark). Upon coming to a stop or if traffic slows, I can see the temperature needle moved toward the red (max). When traffic began moving again, I can see the needle move back to normal operating condition.

The diagnosis at the time was a semi-plugged radiator so a new radiator was installed and the overheating problem appeared to have gone away. Not sure if the problem was completely solved, but with a new radiator and the Chicago fall/winter/spring driving, the cooler ambient temperature may have help hide the problem.

About 1 month ago (June), I noticed similar overheating problem as before despite having a new radiator. The initial thought is that the cooling fans were not starting properly. The fans run only when the A/C is running. It did not appear to start even when the temperature guage started moving toward the red. The fix was a replacement of the engine coolant temperature sensor. This solved the problem of the fan starting when temperature gauge on the dash moved beyond 75%. However, I still have the overheating issue as described previously.

I should note that the car will begin to overheat (temperature gauge touching the red, but no steam from hood) only after 60+ minutes of continuous driving. The overheating is "real" as the coolant overflow reservoir is full and the top cap on the reservoir is wet.

Sorry for the long winded posted, but I am trying to be detailed with the problem. Could this simply be a thermostat problem? Can the thermostat open partially and thus not allowing sufficient coolant to the radiator? Has anyone else has had similar overheating problems? Any help or guidance would be greatly appreciated.

[A&Fbro28]

Thermostat would be the next thing id look at.

[SatinSilver]

Be sure to get an oem t-stat. The universal ones from the autoparts stores do not work nearly as well.

[Honda247]

I was going to say thermostat too.....

[Che]

Does the OEM t-stat from a dealer have 2 temperatures as well? I see some online with 180 Deg and 170 Deg. Which is OEM?

I saw this at rockauto.com for ~$26, but not sure if this is an OEM part.

BECK/ARNLEY Part # 1430707
Original Equipment Standard Temperature; TEMPERATURE=170

How easily can the thermostat be replaced and is there a diagram/instruction for this? Let's just say I am the less than "hands-on" type.

Thanks for the suggestions.

[SatinSilver]

A good place to buy oem parts is www.collegehillshonda.com or www.bernardihonda.com . I'd call them on the phone though if you place an order.

That t-stat you listed does not sound like oem. From what I recall part of the prob with the universal ones is that they open all the way or not at all vs. the oem ones that can open partially. I'd have your mechanic replace it.

I'd also replace the pcv valve every 7 yrs/105k with an oem one. When it goes bad you will start to burn oil. Your car may have two of them...I'd ask the parts dept. about that.

[Fredsvt]

The thermostat wouldn't show itself after 60 minutes, especially with the warm temps outside. In the summer the stat should be open fully in about 5 to 10 minutes max. If it stuck shut, you'd cook really fast. The fans won't have any effect on the temps when moving over about 20-25 mph. Sitting still, definitely.

Does the car have full heat when it's "hot"?

It can't hurt to change it, but I don't feel that is your issue.

What coolant has been run in this car? If you've got conventional green in it, that rad is done again. The reaction between conventional green or universal garbage will cause a reaction that makes the die castings corrode in a way that sends deposits around.

Was the cap changed when the rad was? Last water pump and was it a Honda pump?

The temp going into the red means the car is severely overheated. These gauges are "damped" so by the time it's up there, its cooked.

I'd be watching for bubbles in the reservoir. (not when it's super hot) When it's cold, drain off a slight amount to lower the level in the rad. Smell it, what does the inside of the rad smell like? Coolant or exhaust?

Your heading for block test time.

[SatinSilver]

^^^ Che, since your a new member you may not be familiar with the great advice Fredsvt gives. I'd pay close attention to his post.

[Fredsvt]

The stock thermostat begins to open at 176F and is fully open at 194F. The aftermarket stats, from what I've seen snap open at 195, or whatever they are rated at. It causes a greater degree of thermal shock going from hot (closed) to cold (open) especially in colder weather.

[Che]

Fredsvt - Thanks for chiming in and the diagnostic.

When the new radiator was installed about a year ago, it was done at an idependent shop so the green stuff was used. Until I found this site, I did not realize the green vs blue Honda coolant had that much effect on the radiator.

The car does have full heat when the engine is warmed. I've had to turn the heat and fan to high on several occasions to keep the dash temperature gauge from staying on the red when in traffic. I've also observed the temperature gauge w/ car in park and can see that when the needle goes above 3/4, the cooling fan kicks on. With the fan on, the needle will slowly stop its ascension and work its way back to 3/4 and then the fan would cut off. This will cycle a few times with the temperature rising less after each cycle. This appears to indicate the car is once again cooling down (as long as no additional load is applied i.e. not driven but in park).

The radiator cap was changed with the new radiator. I don't believe this radiator and cap are OEM parts either. The water pump and timing belt (likely not OEM) was also performed at the same independent shop in January 2009 (~6 months ago).

I'll check the coolant quality again, but when I checked the coolant reserve tank yesterday, I did not notice any particular oil or exhaust smell to it. It wasn't super green like unused coolant from a new container, but it didn't have oil or black crud either. I'll check in the radiator next time.

Thanks to SatinSilver's link, I ordered OEM thermostat & Honda blue coolant from Bernardi. It should get here midweek for my weekend project of flushing the cooling system and replacing the thermostat. I think I'm good with the procedures, but I'm not sure if I need to bleed air from the cooling system. Is there a bleeder bolt on the t-stat housing? I tried to feel for it with my fingers, but could not locate it. If anyone as a diagram or photo of this bleeder bolt, I would appreciate your sharing.

[Fredsvt]

I'm not so concerned about the rad not being oem, many of the rads on the outside are just fine. I just hope that the conventional green stuff hasn't gelled and plugged the passages in the bottom of the core. If there's any concern about the cap, get a Honda one, I haven't seen an aftermarket one yet, that holds the same rated pressure or pops off at the same pressure as the oem one.

It's good that it still has heat, that shows, at least, there's some kind of flow and that there shouldn't be combustion gas in the coolant.

I hope they didn't install a rebuilt water pump, it may not be pumping fully, the impeller can be slipping.

The temp gauge should NEVER move, once up to that 1/3 or so of the way up, that's it. The fans should go on and off without even seeing a micron of movement on that gauge.

In order for the fans to come on, the coolant at the outside of the thermostat housing must make the temp switch turn on the fans. If the stat gets stuck shut, the fans most likely will never come on.

The smell of a badly overheated engine is unmistakable, you'll smell what seems like burnt coolant mixed with exhaust. You really shouldn't see any discoloration.

Make sure prior to draining that the heat is turned up all the way. Drain the rad, drain the rear block drain, and if you can do it, pull the forward block drain. You may want to pull the lower hose off the thermostat housing, then take the upper hose off and put it into a bucket, using a hose, run water through the rad backwards.

On the V6 there's no bleed procedure, the radiator neck is the highest part of the system, just fill it slowly, and it'll purge itself. once it won't take any more, put some coolant into the reserve, put your palm over the radiator neck, and squeeze the upper and lower hose. If it needs a little more coolant add some, cap it and start it and let it idle, you should get heat out the vents in short order. Once you do, shut the heater fan off, but leave the temp turned up all the way.

From almost totally empty you should be able to put in around 1.5 to 1.75 gallons.

[12153]

FredSVT:

I strongly disagree with you, respective to replacement radiators.

I installed a new, OEM NipponDenso radiator in my trusty '86, shortly after I bought it. Cost me almost $300. This, of course, was long before the Internet became widely accesible/utilized.

Fast forward, to Year 2001: The engine failed because of my FOOLISH lack of maintenance to the cooling system. Thermostat broke (pin came out of it), head gasket blew, warping the head. Almost crying, as I pulled it apart, I was vastly relieved it didn't damage the short block.

When I put the motor back together, in August 2005, I went with a Koyo "high perf" radiator. Unlike the OEM ND unit, it is solid-copper core, with TWIN flues. Delivered to my front doorstep, it cost me about $112.

Some four (4) years later, I have NEVER had a single problem. My temp guage seldom ever gets above 3:30 clock position, regardless. But I'm STILL going to let you kick my A$$ for installing GM Dex-Cool instead of Honda Type 2 (blue). I flushed it out about a month ago, replacing the thermostat, all the hoses, and the heater control valve.

If/when the radiator needs to be replaced in my '02? I'm going with a Koyo, or otherwise. On the other hand, if YOU want to buy me an OEM ND unit, I don't mind spending YOUR money, Sir!

My local Honda dealer will NOT install an OEM (ND) radiator, except upon explicit customer demand, in WRITING. NO. They pick up the "horn," call the NAPA dealer, right down the street, and save the customer 2/3 to 3/4 on an aftermarket radiator which works just as well, and lasts just as long as OEM.

[Fredsvt]

Robert,
Nowhere did I say anything about putting in an OEM (from Honda) radiator.

I said that the rads available from the outside are fine. I install them all the time. These are usually Visteon, or Koyo OEM "style" rads.

However, I'd never install an "all metal" copper/brass rad in one of the newer Hondas with all aluminum engines. If our supplier sends us one I send them back.

Dissimilar metals, especially with copper/brass/LEAD (solder) and that much aluminum can cause all kinds of odd electrolysis issues. I've never liked them to begin with as in our area the cores rot out from the outside in long before the insides fail.

Your '86 should have a cast iron block, correct? I wouldn't be as concerned, as you already have a large amount of dissimilar metals in contact with one another. That being said I'd never go any more than 30k on coolant changes in that car.

[12153]

FredSVT:

Fair points, Kind Sir!

The "A20A3" engine in my trusty '86 involves a cast-iron block, with an aluminum head. Despite other (chemical) factors, IRON and COPPER tend to "get along" quite well, Sir.

But with the all-aluminum engine in my '02? I will DICTATE to Koyo (or other vendor) that they furnish me an ALUMINUM-core, if/when radiator replacement is necessary.

[Fredsvt]

The iron and copper get along fine, yes, but the lead in the solder sure doesn't, and the brass is pretty much sacrificial.

I've seen many of the "all metal" rads that were put in elsewhere and the top and bottom (or side) tanks end up paper thin.

Older all cast iron engines like many of the diesels I see have original copper/brass rads at 20 years or more.

I'm trying to remember the last alum/plastic rad I changed on a later model Honda. Only two comes to mind, one a kid who tried to change his own oil, and didn't use the proper jacking point and crushed the bottom of the rad.

The other a '93 Civic with a plugged rad. It would try to overheat if you kept it at 5000 rpm or more for about 20 minutes. That girl used to drive like a maniac on the highway.