Ericjergs

Car has d15b7 motor, manual tranny, and is completely stock with 136k miles on odometer. Beginning to think it's been swapped with how many problems I have with it...but anyway!

My Civic only overheats on the highway, and by overheat I mean a little above half at the most. I turn on my heat and slow down a bit to avoid any damage, and can continue without any trouble. In colder weather 30F-40F it takes awhile for it to overheat (Going atleast 80+ for 15 or so miles) but now that it's getting warmer it happens everytime with little effort.

So far I've...
-Had my coolant flushed by a shop that did it with a machine, and they said they only got dirty coolant out. (Not coolant with oil in it, just dirty because I'm sure the thing has never been flushed. Previous owner obviously did not do any maintenence)
-Replaced thermostat (End of last summer)
-Replaced temp sensor (End of last summer)
-Replaced Rad Cap (End of last summer)

The mechanic shop re-filled and I'm assuming purged any air out. The trip to the shop was recent (2 weeks ago) and the coolant in both the resevoir and radiator has remained at the same spot whenever I check. When the car is at operating temp the resevoir IS NOT overflowing or anything of that nature. Everything seems to be completely fine. There is no white smoke coming out of the tailpipe, the exhaust doesn't smell sweet, the coolant does not have oil in it, and the oil is not milky. When I was at the shop I also had them do a valve adjustment and he said everything checked out okay under the valve cover. The oil on the dipstick is also fine.

So I'm guessing it could possibly be the water pump not pumping well enough at sustained higher rpms? Whenever the radcap is off and I rev the motor coolant shoots out...that means the water pump is working, correct?

Lastly, fan turns on at appropriate times, and it won't overheat around town, in heavy stop and go traffic, or when I'm racing my powerful 100hp engine through the idiot drivers in town. The heater core is also slightly clogged...takes a few minutes longer than it should to heat up, but nothing horrible. I read that this doesn't have any effect with overheating anyway, right?

hannslebo

Purge/bleed the system again...if you're not sure they did it

Ericjergs

Thanks for the quick response, but I live on a college campus and don't really have any jacks stands or an inclined area to do this at, and I have to do it from the rad cap and not the actual purge valve on the upper water outlet because I've broken the stupid bolt on that thing twice already, and the junk yard doesn't have any left. Haha
Any other suggestions I could do in the mean time?

motegicivic

I am thinking bad water pump, if the coolant was never done the blades on the water pump could be eaten away.

Another thought could be bad radiator as well.

redm3turbo

I was thinking partially clogged radiator ---


to bleed your system though in a college setting...take off radiator cap. Turn heater vent to heat (Doesnt have to be on persay, but it has to be on heat)
Let car run 20 mins. You should periodically add coolant as well. You can lower the hood and let it idle though so people dont noticed. (I bled my system at work once), it works though

andyz

I had similar symptoms and it turned out to be massive scale buildup in the radiator.

Its not that hard to see, just get a turkey baster and while the car is cold...open the radiator cap and siphon coolant out until you can see down there. The mechanics at the shop may have overlooked it because some is unavoidable , but whether some is too much is only left to the driver who needs good heat radiation doing 80 on a hot day.

grumblemarc

iTrader: (4)

Bad rad if it's doing it while moving.

Ericjergs

Well I was told the radiator had been replaced...It also looks fairly new. But I'll give that a looking into. I really don't trust anything the guy said when I bought the car, it may still be the original, lol.
I also forgot to mention a few months ago I bought some of that stuff you run through the radiator that is supposed to break up all the junk inside, and ran it through my system while I drove around town and on the highway. Is that effective at all, or effective enough to rule out a plugged radiator?

Also, do I not have to be on an incline to get the air out of the system?

Thanks for all the help guys!

motegicivic

What is the name of the product? I never heard of a product that break things up only stops leaks.

To get rid of crap in there typically you flush.

I am still thinking water pump.

Ericjergs

Similar to this product...

http://shop.advanceautoparts.com/web...T%7CGRP2053___

And yeah I've had it flushed, but I'll buy a turkey baster tonight at walmart or something to see if I can see any deposits, haha. If I can't tell with that, I could get a cheapo thermo gun, and check the radiator with that right?

motegicivic

Those products are designed to be used as flush you put them in per instructions then use water to flush it all out.

Themo gun will do you no good, take some coolant out of the radiator opening, take a flash light into the opening and see if you see white build up or other build up, super hard to see inside.

If the radiator is new or seems newer prob the water pump, do you have any leaks under the timing belt cover area, leave the car overnight and check for leaks under that area.

slatermvp

I had the same issue after my radiator was replaced and it was due to the water pump overheating. I changed my radiator because it had alot of junk build up. Have the system flushed or try another radiator.

Ericjergs

Okay I bought the turkey baster and a flashlight to check inside the radiator. Will have it done and my results posted whenever I have time. I'm thinking this weekend I should have it completed, because I have class till then.

And no, there aren't any leaks anywhere. I DID have a pressure leak before(or alteast I think) because I was loosing coolant on the highway and one day I drove the car pretty hard around town, and when I parked two bypass hoses had split to where it was noticably spraying all over the engine. But I don't think thats the problem as I'm not loosing coolant anymore.

CFiannotti

I hope you replaced those bypass hoses! I had one of mine split near the end, overheated, and wound up replacing the engine (it croaked the HG by 2 years later)

teo032

After your engine has been on for at least 10 minutes, check the lower radiator hose and see if its warm/hot. If it's cold, it could be thermostat (that's what was wrong with mine thank god) or the water pump. Might be other things, but this would help isolate some problems.

BTW if it is the water pump, might as well do your tranny belt.

edit: I know you replaced your thermostat last year, but who knows, maybe it went bad somehow. Doesn't hurt to take it out and throw it in some boiling water and see if it opens or replace it with another one.. $16 compared to waterpump replacement is a lot better imho.

civicsi_guy

Also chech that the fans are blowing in the right direction pulling in to engine bay cause if not then while driving the fan will be pushing against the incoming air and it will cancel out the incoming air and not let air pass over the rad I've worked on a few cars with that problem

Ericjergs

Yes I changed those hoses out! And yeah both fans are blowing the correct way.

Radiator doesn't look that bad inside, although I don't really know what to look for.
I was with an older guy who has worked on cars for a while and he insists it is my thermostat. His reasons for saying so are the radiator hoses were not nearly as hot as they would be if it were working, and there wasn't any flow of coolant within the radiator while idling, and it got hot enough for the fan to come on a few times).

What do you guys think?

andyz

You may have the wrong thermostat in there.

teo032

Just change the thermostat, it should be a quick job, no longer than an hour.

Ericjergs

Yeah I just bought a Duralast one that opens up at 170 degrees, which was the lowest they had. But I'll change the thermostat whenever I get the chance, and give you guys an update afterward. Should have done either wednesday or thursday.

delsoltech

Sounds like the water pump, hope it's the thermostat though for your sake.

CherokeeInk

Make sure the little pin on the thermostat is at the top when installed. Upside down thermostat could keep it from opening all the way

Ericjergs

Oh really? I didn't know that, well I'll make sure to install it correctly. And by "pin" you mean the little piece of metal that goes through the larger part of the thermostat and can kind of move around right?

Ericjergs

Old thermostat was upside down! Hahaha, so I changed it out with the new one, and...it still overheats on the highway lol.

So...water pump?

Edit: Oh and I also let the air out of the system through the radcap. Fan came on twice, heat was on, etc etc, BUT the car was only on a "slightly" inclined parking spot...

RVD9431

this is happening to me on my 96, the temp would go up to 3/4 sometimes only while after driving for at least 15 mins, flushed the hell out of my radiator, a lot of rust and what looked like coarse sand came out, bled the system, still did it but to only 1/2 on the gauge, reflushed the system with a hose extensively and replaced thermostat, STILL does it but even less than the second time.....my radiator isnt corroded, Im thinking corroded water pump, the belt and pump are old, idk how old as i just bought my car (176k) but it definitely needs to be done, ill let you know my outcome saturday when I replace the pump and belt.