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I have a 1994 Honda Prelude with a H23A1 engine, and she overheats. The engine has 210k miles on it and I never knew anything of the history, but she always had this problem, driving for about 15 min she would stay at normal operating temperature, soon after that the temp starts to climb especially at idle and low speeds, The water pump started to leak coolant from the weep hole so I replaced that as well as the timing belt. I changed the thermostat with a aftermarket and OEM one with same symptoms, I have the OEM thermo in my car atm. I own a spill free funnel so I’ve bled the system everytime I opened the cooling system. Hints, there is some sort of stop leak the previous owner put in the radiator. It looks like glitter, I’ve flushed the block and radiator with water 3 times and the stop leak is still in there. While using the spill free funnel I filled it with coolant till half way, then I squeezed the top rad hose and debris came out from the radiator like dirt or something. Don’t seem to notice this debris elsewhere. On top of the radiator where the plastic tank meets the aluminum core has dried white stuff on it. Replaced the cap 3 times and when I turn it it never locks into place. At idle with the hood open the temp stays at normal, as soon as I close the hood the temp will climb, No debris in front of the rad or condenser. The temp will go up a bar then back down to normal then back up then down and repeat. Compression is 180 across. Is this a sign of a clogged radiator?
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i will revew all the things that can cause a over heat that i can remember, and then link you too erics diagnostic stuff.
air in the cooling system if it is not bled properly air bubbles cause hot spots where the engine is not being cooled.
lack of coolant, not enough coolant circulating too cool the engine properly.
a stuck closed thermostat.
a radiator that has crap stuck in its fins so air cannot flow through it.
a radiaor that has corrosion, gunk, dirt, or crap such as stop leak clogging it.
a radator fan that is not functioning properly causing over heats at stand stills or low speeds where air flow from the car moving forward will not be sufficient enough.
clogged coolant passages clogged buy stop leak in the engine or other areas.
blown head gaskets that allow combustion gasses too go into cooling systems causing a spike in coolant temps, this is evident if coolant seems too fill the over flow tank, bubbles in your cooling system when it runs, also… this can be confirmed buy doing a combustion leak test, when a head gasket is blown sometimes you will find coolant in oil/oil in coolant, or even have lots of steam coming out of the exhaust, low compression especially in the case of neighboring cylinders, and if your spark plugs on those cylinders look steam cleaned.
a clogged AC condensor that air cannot pass through because leaves and dirt won’t let it, turning it on causes the AC condenser too get very hot and since its next too the radiator it heats up the radiator as a result.
bad coolant temp sensor can say your engine is over heating but it isn’t
also see this.
http://www.ericthecarguy.com/faq/what-to-do-when-your-engine-overheatswatch this too and make sure you have bled the system properly.
[video]http://https://www.youtube.com/watch?v=zUpXgAJ1gjU[/video]Was replaced with a OEM unit. The old thermostat was clean, the stop leak that is in my system looks like glitter.
This certainly looks like you have a radiator that is corroded inside. Aluminum radiators stay look good on the outside but corrode on the inside. i would change that radiator out, it seems to be the only thing u havent done yet. The fact that it stays cool when the hood is open also makes me think of airflow being a problem so check on your fans and make sure they engage when they need too.
that is a good test, how warm does your radiator feel when your car reaches operational temperature? it could be corroded and clogged with stop leak. a radiator that is full of corrosion will typically not work as well when the car is at a stand still, when the car is moving forward the radiator can now work efficiently enough.
the stop leak that has the glitter like substance is typically some attempt at a cheep o fix for head gaskets, but i don’t like it as it can clog things up really bad and cause overheating itself such as clogging up your radiator.
[video]http://https://www.youtube.com/watch?v=76GpMD4LIwY[/video]
There’s a coating of stuff like in that video in the exact same location on the top radiator neck. I don’t think the head gasket is blown since compression is solid and no smoke or anything. She started to heat up more now since summer is here in Cali, she lasted a while where she didn’t overheat but I think the stop leak is catching up. Gonna replace the radiator and see what happens.
i advise first feeling how the radiator is decipating heat during operational temperature first before replacing it, its a likely cause but its still good too diagnose before replacing parts. 🙂
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If the stop leak was not used properly it could have caused a blockage in the system. The radiator is particularly susceptible in these situations because of the small passages and that’s where they put the stop leak into. You might remove the fans and check across the fins for temperature differences. If you find a ‘hot spot’ or ‘cold spot’ in the fins, then this might be the case. An inferred thermometer works great for stuff like this. They’re pretty cheap these days.
As for a head gasket issue, you can use the info in the video in the article that was posted to check for that. It’s the video on diagnosing overheats.
Good luck and keep us posted.
So, my radiator was old and leaking all around the sides so I went ahead and replaced it, the thermostat looked like it had some kind of green residue that I never seen before even on the old aftermarket tstat. It also looked scratched right below the spring where the green thing was, maybe that’s normal? Anyways, that was a new OEM Tstat that I put in about 1 month ago, so I really doubt it’s that or somehow it came faulty. I went to work 15 min drive or so with no issues, I went home and when I was backing up it overheated 1 bar, then back down fairly quickly, I shut off the car. Later that night I went for a drive to see how it acted cause I put in the new radiator, and I bled the coolant with my spill free funnel and I saw the bubbles come out. Driving about 10 min was fine, 1 mile away from my house it overheated coming to a stop, As I drove the temp went down to only 1 bar above normal, but it kept rising even if I picked up speed, I turned on the heater and the temp rose even more! I stopped, shut her off and opened the hood, waited a few min and then turned her on again and observed the fans once again. The fans came on and the car never overheated, stayed like that for a good 10 min with no overheating, I close the hood and As soon as I get in the car it goes up a bar, then back down and sit there for a good 5 min and temp stays normal. I pop it in drive and as I press the gas the temp starts rising fast, And I just went down like 2 houses at like 8 MPH, I’m crying inside at that point. My water pump started to leak about 1 and a half months ago so I had it replaced as well as my timing belt, new radiator/radiator cap, and new thermostat. Fans come on at the right time, Does this leave the head gasket? I don’t lose coolant, No white smoke, compression was even at 180 all across, I don’t know what to check anymore, really. If I have a infrared thermometer what should the top rad hose temperature be once at operating temp? Maybe temp sender is bad? Can it be the thermostat sticking when driving? Water pump was faulty? I have the exhaust manifold heat shield off Idk if that can cause overheating. Any ideas on where to start again?
Put a scan tool on it and see what temperature the engine computer says. Sometimes temperature gauges go whacky.
I don’t believe that makes it impossible. I used to drive an obd1 car and I remember all sorts of tools and downloads to read these computers. People complained when obd2 came out because the computer did more and hence was slower.
Everything you describe sounds like air in the system. I’d wager air is getting in there somehow or you’re not bleeding the system correctly. Preludes can be tricky with that. Make sure the heater temp is on Hi and the fan is off when you bleed the system or air will still be trapped. If you’re certain that you have all the air out, then it may be time to look into the head gasket theory if you’re not able to find any external leaks.
http://www.ericthecarguy.com/faq/what-to-do-when-your-engine-overheats
Keep us posted.
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