By on June 25, 2009

David Holzman writes:

There was a killer traffic jam on the way into the Holland Tunnel from the NJ [turnpike] last weekend. I covered a mile and a half in about 40 minutes. At the start of that jam, my 99 Accord (manual and 159k) began overheating. When the scan gauge said the temp was 231, I put the heater on full blast, and kept it there, which brought the temp down below 216. (In normal driving, the temp stays within a few degrees of 182.)

In Manhattan, I tried putting water in the radiator, but it only took about 2 cups before it was full. Leaving Manhattan, traffic was thick but not stop and go on the West Side, and the temp remained in the 190s-200s (I can’t remember if I had the heater on or not at this point), and once the highway was clear, the temp remained below 190 and mostly around 182 without the heater on all the way back to Boston–as it had been from DC to the Holland. Haven’t had any trouble driving around town since. Car has a 3 month old t’stat. I took it in, and they couldn’t get it to overheat. Any ideas?

Sajeev replies:

First check your cooling fan, it should kick in around 190 degrees. An easy way to check is to run your A/C, since that normally kicks on the fan too. But I seriously doubt that’s the problem.

On an older car with high miles, I’d guess the radiator is clogged just enough to cause a problem in severe traffic in the summer months. And it’ll be fine every other time. At least for now: get a new radiator if you suspect it is original. This is more important than ever, since most new(ish) radiators use plastic parts that are prone to crack far quicker than conventional metal parts.

Get the latest TTAC e-Newsletter!

43 Comments on “Piston Slap: The Heat Soaked Honda...”


  • avatar
    John Horner

    Any signs of exhaust gas in the coolant? A small head gasket leak might be exacerbated by a traffic jam slog. It doesn’t take much mixing of exhaust gases and coolant to cause a big problem.

    Smart move using the heater, btw. Not many people these days realize that the heater can be used as an emergency auxiliary cooling system. Passengers may think you stark raving mad for turning the heater on full blast when stuck in a traffic jam and the temperature is over 100 degrees F outside. Been there.

  • avatar
    jpcavanaugh

    I agree with the plugged radiator. I have seen this in older cars. Also, not much capacity there, and the plugged radiator coupled with a smidge low on water could make it worse.

  • avatar
    dolo54

    If you are really cheap and handy you can backwash your radiator. Leaves and dirt build up in the radiator fins and keep it from cooling as much as it should. Take out the radiator and with a hose spray the back of the radiator washing the gunk out the front. When it’s clean put it back in. A new radiator shouldn’t cost more than $100. They are fairly easy to put in yourself. A mechanic shouldn’t charge more than a hour service time to put it in, depending on their hourly rate $50-$75.

    This is normal problem with an older radiator. Moving, the wind goes through and cools no problem. In slow stop and go, no wind, the fan isn’t strong enough and the gunk in the radiator keeps it from cooling.

  • avatar
    mikey

    I don’t know about Hondas,but I know that with an old rad,the cooling fins will rot away from the cooling tubes. The rad looks fine but its just not doing the job. Or as Sajeev pointed out the rad is plugged. Either way you need a new rad.

    David…. be very wary of junk yard rads or any used rad for that matter. A can of black spray paint will do wonders for an old rad. It will still be a piece of junk,albeit a pretty one.

  • avatar
    rm

    I had a similar problem with a late 80’s Mazda. Turned out the crimp for pins in a connector to the relay for the cooling fan had corroded so badly that there was, at best, an intermittent connection for the fan. Normal driving provided enough air that I never knew until being stuck in a traffic jam.

    The electrical connectors in those cars were the same Molex connectors you see in computers, which are not appropriate for automotive use. I assume that by ’99 Honda was using something with much better environmental protection for the connectors.

  • avatar
    Billy Bobb 2

    The “heat blast” option worked on dad’s Impala.

    Modern vehicles don’t have heater valves.

    The heater core is always hot.

    Blend doors are controlled by the heater temp knob.

    Aftermarket t-stats are shit.

    Your electric cooling fan failed to cycle on, my guess.

  • avatar
    snabster

    I’ve never understood the connection between “plastic parts on radiators” and “old cars gets plugged up radiators”. I’m not doubting, just trying to understand what is happening here.

  • avatar
    Pch101

    I agree with the radiator comments. A bad radiator seems to be the likely culprit; that’s the right age/ mileage for them to fail, and the symptoms match that to a “t”.

    The fan might also be an issue. But I’d check the radiator first.

  • avatar
    JT

    Check the simple stuff first…Since it only took a cup or two of water, leaks are likely to be small or nil.

    My experience is that modern-ish Honda products should idle at or around normal temps almost forever if everything else is OK.

    –backwash the rad fins to get leaves, etc out.
    — Is the electric fan coming on? Possibly a bad or lazy temp sensor not engaging when needed. Also, check related fuses, relays, etc. Not impossible to have an intermittent connection on an older car.
    — Does the car have A/C? If so, the second elec fan should kick on when the A/C is commanded on.
    — Change the coolant. Good maintenance anyway, and fresh coolant will help de-gunk the rad.
    — In spite of “urban legend”, that plastic tray or liner under the front of the engine IS important to airflow and heat exchange. If yours is missing, replace it to improve the airflow out of the radiator.
    — And of course, consider the one-in-a-million chance of something really weird…a plastic bag momentarily blocked the rad or grille, then blew off as you got up to speed. (One of Carl Sagan’s “singular aberrations.”)

    As others said, high points to you for kicking the heater on. Good save.

  • avatar
    USAFMech

    I’ll also add the water pump to your list. If, for some reason, it is not up to the job anymore, it’s a pretty simple fix. The other answers above are more likely, though.

  • avatar
    roadracer

    A number of years ago I had a Nissan radiator corrode from the outside; the fins corroded away even though the inside was clean and sound. I suspect the radiator, if the fan was bad it would have overheated in the heavy traffic also.

  • avatar
    Lokkii

    I’ve never understood the connection between “plastic parts on radiators” and “old cars gets plugged up radiators”. I’m not doubting, just trying to understand what is happening here.

    There is no corelation. It’s simply another area of weakness in a radiator.

    Plastic is not an issue in this case, since there’s no leak. However plastic parts ARE the cause of a lot of radiator failures…. Say in my 1998 BMW for example.

  • avatar
    SunnyvaleCA

    In Manhattan, I tried putting water in the radiator, but it only took about 2 cups before it was full.

    Hmmm…. don’t modern cars have radiator caps that won’t let you open them if there is pressure? Also, it bears repeating here that you should never overfill your radiator. There is a “fill line” in the overflow tank. If you completely fill the system, the pressure in the system will spike massively when heated until something bursts. You need to leave that extra air in the overflow tank.

  • avatar
    rnc

    Word of warning for anyone driving a late model Jeep Cherokee. The heater (atleast for ones in south) uses the hot coolent to deliver heat, tried the “switch on heat trick” (in winter) and pulled what small amount of fluid I had left out of the radiator (as the thermostat has to have contact with fluid to register, it didn’t and did not give an accurate reading of how badly I was over-heated) the head gasket was quickly toast. NOTE: The heater/radiator inter-relation for Jeeps was explained to me by the mechanic.

  • avatar
    poltergeist

    Billy Bobb 2 :

    The “heat blast” option worked on dad’s Impala.

    Modern vehicles don’t have heater valves.

    The heater core is always hot.

    Sorry Billy Bobb…you are wrong. The Accord has a heater valve that controls coolant flow to the heater core.

    I’ve seen water pump impellers corrode away if the cooling system has been abused (ie. been run with straight water for long periods). Can cause all sorts of intermittant overheating depending on engine speed and load.

    First thing is to make sure the fans cycle properly and make sure you have a good thermostat (the OEM ones really are better than most parts store ones IMHO).

    ..and if it’s a 4 cyl (you said 5speed right?) make sure you bleed the cooling system properly with the bleed screw on the thermostat housing.

  • avatar

    I’m pretty sure I got a radiator about 4 years (80k) ago, but probably haven’t flushed it.

  • avatar

    @Sunnyvale
    I let the thing cool for about 45 minutes while I relaxed w/ espresso at Joe’s The ARt of Coffee, which has–for those who appreciate this–the best espresso I’ve tasted anywhere. My recollection is that when I put the water in, the temp had gone down to about 150. The cap unscrewed easily. The water did not go over the fill line in the overflow tank.

  • avatar
    Pch101

    Since the radiator is only four years old, I’d begin by flushing it. That may be enough.

    If it was original equipment, I’d skip the flushing and just replace it, as it is unlikely that a ten-year old, well-used radiator is going to be saved with any amount of maintenance.

    In the future, I’d take better care of the cooling system. Four years without maintenance on a ten-year old vehicle’s cooling system is a bad idea. Newer cars can handle longer intervals, but I wouldn’t let it go too long on a ten-year old car. I’d be flushing it every couple of years.

  • avatar
    mkII

    Well whatever you do with dismounting the radiator, don’t forget to let it cool down completely first. Sounds simple, but just don’t ask why I know this….

  • avatar
    poltergeist

    ..and…both fans should come on together on this model. If you only see one fan running, you’ve got a problem with the fan motor and/or circuit.

  • avatar

    Lokkii : Plastic is not an issue in this case, since there’s no leak. However plastic parts ARE the cause of a lot of radiator failures…. Say in my 1998 BMW for example.

    When it comes to a radiator that’s over 8 years old (in my experience) with high mileage, its only a matter of time before the plastic parts crack and the radiator dies.

    I’m all about making cars lighter and better, but I do miss the days of 100% metal radiators.

  • avatar
    chuckR

    Another singular occurrence – one of the hoses partially collapses. Had that happen to me – by the time I got the hood open, damn thing sprang back and looked OK. It was just a little slow on the rebound the last time and I caught sight of it. That was a lousy old Fiat; I’d expect better of Honda.

  • avatar
    skor

    Overheating can be caused by anyone, or a combination, of the fallowing:

    Bad water pump — impellers are made of plastic and disintegrate.

    Bad t-stat.

    Clogged rad.

    Bad electric fan.

    Bad fan electric temp switch(sensor).

    Collapsed rad hose — very common with lower hoses.

    Air leak into the engine causing a lean mixture.

    Bad head gasket, cracked cylinder head.

  • avatar

    UPDATE: I checked, never got new radiator. Very noticeable concentration of bugs, but I can’t see or feel any corrosion. Haven’t checked fan function yet. The car runs and idles smoothly, which makes me doubt any gasket problem.

  • avatar

    Thanks to all who are giving advice

  • avatar
    doctorv8

    Rule out the simple stuff first: Make sure there is no debris in front of the a/c condensor, or between the condensor and radiator. 159k worth of leaves, or worse yet, a plastic grocery store bag may be the culprit…and the fix is free!

  • avatar
    John Horner

    I would certainly verify that the cooling fan and thermostat are working reliably before assuming a collapsed radiator.

    Personally I don’t find modern plastic & aluminum radiators any more trouble prone than the old brass & copper ones. Thirty years ago it was common to see vehicles pulled off on steep hills due to overheating. Now it is rare.

  • avatar
    poltergeist

    skor :

    Bad water pump — impellers are made of plastic and disintegrate.

    On this car (and virtually all Hondas that I can think of) the water pump impeller is stamped steel.

  • avatar
    Steven Lang

    Okay, David. This is how it goes.

    1) Make sure the radiator fans are clicking on and going at a rapid rate. Just let the car idle and wait until the temp starts climbing. If it doesn’t click on past the 215 degree mark, you will either need a new relay or assembly.

    2) Squeeze the hoses. Are they extremely soft? Do you smell or see any leakage? That too can be a problem.

    3) I replaced the radiator on my Camry after 10 years… just as cheap insurance. Go to radiator.com and you should be able to order one for less than $100.

    4) Flush out the fluids if you haven’t done so already. You can actually buy a manual excavator for $50, remove the radiator cap, and just start pumping away until it’s dry. Start the vehicle up for a minute and repeat a couple more times.

    Let us know how far you go… best of luck.

  • avatar
    poltergeist

    On newer plastic radiators the tanks usually get brittle and crack.

    Old brass/copper radiators used to split their soldered seams.

    They both fail fairly regularly when they get old, there’s just no good way to “repair” the plastic ones like we used to do with metal ones.

  • avatar
    guyincognito

    If the coolant hasn’t been changed in several years, that could account for part of your problem. Water actually transfers heat better than coolant, but it can also evaporate over time. If you haven’t got enough water in the system it would not cool correctly.

  • avatar
    Samir

    Reminds me so much of when my radiator FUBAR’ed itself on my 1995 Neon (student car; don’t judge!). I too blew all the heat into the cabin. Driving around in a car cabin with an internal temperature of 105 degrees wasn’t fun until I could buy a new radiator, but it built character.

  • avatar
    rodster205

    I had an identical problem on my identical-in-every-way 1998 Accord. You have TWO cooling fans on that car, one for the temp and one strictly for the A/C. With the A/C button on BOTH fans should be running. If not, that one that’s not is dead.

    BTW, an easy/cheap DIY fix to replace the fan with one from Advance/Autozone, but make sure to get one with the blades and shroud already on, then just unbolt, yank out, slide in the new assembly, bolt it down. Don’t forget to plug it in though!

  • avatar
    shaker

    If the heater core can bring the temperature down as much as you said, I’d guess that the water pump is working well enough- either the electric fan/thermal switch is wonky, or the radiator is partially clogged.

    An outside possiblity: Was the new thermostat installed correctly? (I don’t know if this particular one could be installed backwards)

  • avatar
    dolo54

    FYI – I’ve had this problem on two older cars, one an Integra. A new radiator fixed this problem on both. Both cars had the problem in summer nyc stop-and-go traffic only. Would not overheat on the highway or normal city driving, just in daytime traffic jams. Both cars were fixed 100% with a new radiator.

    It’s not your thermostat because if it was, it would either be stuck open and the car would not overheat but wouldn’t get to proper operating temp in the cold (which you would have to wait til winter to find out), or be stuck closed and the car would overheat all the time.

    It could possibly be a fan, but you can’t tell from idling because often the fan will not need to go on until you are in an overheat situation. You would have to get the car to the point where it is overheating and then see if your fans are working. However if your radiator hasn’t been replaced in more than a few years I would suspect that as the most likely culprit. New York City is very dusty, more than almost anywhere else and I think it clogs radiators quicker, plus I needed to change my oil more often, but that’s another story.

  • avatar
    cnyguy

    Your car has (or had) an air pocket that you installed with the new tstat. Hondas (and other fwd cars) are notorious for this- a small bubble of air gets trapped in the highest part of the cooling system which is why Honda puts a bleed screw in the tstat housing. The air bubble does not transfer heat very well, causing the tstat to not open fully. The pocket has probably worked its way out of the cooling system by now, but you might want to grab the shop manual and bleed the system by the book.

  • avatar
    rpn453

    First, make sure the fan turns on with the A/C, and that it also comes on when the coolant gets hot. There’s no point in doing any further troubleshooting until we know that.

  • avatar
    MBella

    It’s going to be the fans. If it’s fine when you are moving, but when idling it overheats, that is the only thing that could cause that problem besides a head gasket. Anything else, clogged radiator, water pump, thermostat, etc… would reveal themselves at other times as well.

  • avatar
    golden2husky

    It could possibly be a fan, but you can’t tell from idling because often the fan will not need to go on until you are in an overheat situation. You would have to get the car to the point where it is overheating and then see if your fans are working…

    Uh, no. The fan(s) will come on when the engine exceeds a preset temperature to prevent the car from overheating. If they don’t start to run until after the temperature is too high, something else is wrong.

    I really think the fan, relay, temp sensor, etc are all more likely than the radiator itself. Interesting to note that sometimes with an electric fan setup such as this, turning the A/C on may force the fans to run, causing the engine to return to normal operating temperatures. This will not work if the fans are bad or ther A/C system is dead, but if for some reason engine temperature is not engaging the fans, commanding A/C is supposed to command the fans to run all the time to force air across the condenser coils.

  • avatar
    happycamper

    I’ll throw something completely different in the list. I own a ’98 Honda Civic, manual transmission. In certain rare weather conditions, it will idle as low as 200 rpm. I too have had the car unexpectedly start to overheat while idling in rush hour traffic.

    I took a while, but I figured it out. When the car idles at 200 rpm, the water pump might not generate enough pressure to open the thermostat. Simply tapping the gas pedal will generate enough pressure. Try this next time, it might solve your problem.

  • avatar

    happycamper : When the car idles at 200 rpm, the water pump might not generate enough pressure to open the thermostat. Simply tapping the gas pedal will generate enough pressure. Try this next time, it might solve your problem.

    Thermostats open when coolant in the radiator hose reaches a certain temperature, it’s not about water pressure (singularly). But that’s besides the point.

    What you are saying is not very likely, I don’t think any motor can idle at 200rpm, no matter what your tachometer says. But if I’m way off base there, you might have a point: what you said is a big problem for modified cars running performance engine pulleys.

  • avatar
    rodster205

    As I said before but apparently my words are invisible, I had the exact same car with the exact same problem. It was one of the fans.

    As another poster said ANY speculation or other testing is pointless until the owner takes FIVE SECONDS and turns on the A/C and looks at BOTH fans. If BOTH are not running, problem solved. If both are then you can chase bubbles, leaks, water pumps (very unlikely) etc.

  • avatar
    altarr

    So I found this thread when looking for a solution to my own problem….it is a quite a nunique one and anyone with help for me is greatly appreciated…

    I have a 2004 Honda.

    This winter, I would start driving and the temp gauge would go to its normal position, however, I would not get heat AT ALL when driving in the city. Once I hit the highway and the engine began revving harder, heat would blow. Same goes for hills, the heat would blow for a bit but then go away when I took my foot off the gas.

    Now, flash forward to our warmer weather of spring. When I try to run the heat, the car almost instantly overheats (and no heat to boot) By overheats, I mean the needle is pegged at max. This happens on the highway and in the city. The car will also slowly start to overheat even with the heat off when idling. (like at the slowest burger king ever) Also, even when the heat gauge is at max, there will only be cold air coming out.

    Any ideas?

Read all comments

Back to TopLeave a Reply

You must be logged in to post a comment.

Recent Comments

  • Lou_BC: The lede should have been, “Toyota Corona. a Novel car.” ;)
  • FreedMike: That’s the anti-Biden term for the DerpConservative crowd. I mean, “Brandon” is just...
  • FreedMike: @dal: Seriously, it’s like the company traumatized him. Maybe he came home from school early one day...
  • FreedMike: Well, then, I don’t think the Mach E does much to influence Maverick sales one way or the other.
  • 65corvair: It looks like a Chevy. The front bar on the grill is the biggest offender. No way would I buy a first year...

New Car Research

Get a Free Dealer Quote

Who We Are

  • Adam Tonge
  • Bozi Tatarevic
  • Corey Lewis
  • Jo Borras
  • Mark Baruth
  • Ronnie Schreiber