glokul

So my Civic just hit 250K the other day and now it seems the problems are coming one after the other. The main issue is overheating. A couple months ago I sprung a leak on one of the hoses going to the heater core. Replaced that and everything has been fine up until about a week ago when the other hose to the heater core sprung a leak. I'm only now thinking this might be a clue, however it may just be coincidence. So I replaced that hose last week thinking I fixed the problem.

However, all during this week it's been overheating while idling or going really slow, but I've counteracted that by turning on my heater. I'm thinking it's either a bad thermostat or possibly bad fan switch, so I order both of those to replace today, which I did. It still overheated so I took out the radiator and flushed it. Still overheating. Upper radiator hose is hot, lower is cold. The fan is not coming on because it's just not hot enough at the switch, correct? I jumped the fan switch, which turned on the fan, so I know the relay is good.

There is no leaking, and the oil is not milky. All that's left is a bad water pump or a clogged heater core, or am I missing something? I removed the top radiator hose from the radiator to see if any coolant would shoot out, which it didn't. Not sure if this necessarily means the pump is bad, but I would have thought something would come out. Tomorrow I will blast some water through the heater core to make sure it's not clogged to rule that out (the fact that both heater hoses sprung leaks makes me think this might be the issue but I really don't know).

Any other ideas? I think I've tried everything so far, but maybe not. Thanks for any help!

Wankenstein

Let me guess.. the heater hose located under the distributor: which most likely has an o-ring oil leak.

Or blown headgasket or failing/failed waterpump.

Do a coolant system pressure test while engine is cold. Could have a small leak the while engine is hot and burns off before you see it. Thoroughly (remove air intake) check throttle body coolant hoses and heater core.

Just one of several signs of a breached headgasket (http://www.agcoauto.com/content/news/p2_articleid/200) and rarely shows up in Civic engines. The most telling breached headgasket symptom is coolant loss in radiator combine with coolant gain in the reservoir. Do a block test as described in article.

Very unlikely. You stated you ran the heater to prevent overheat... if it was fully clogged it wouldn't produce heat. Partially clogged? maybe,,but, still doubtfull unless some jackass used headgasket sealer.

To check waterpump..look inside radiator (cap off) at operating temp and check for swift coolant flow in one direction while revving engine. Obviously, take caution opening rad cap..stand back as far as possible, use a rag to avoid burn and open halfway to allow pressure out before fully removing. Or..from cold start remove rad cap and allow to get hot enough to open thermostat and then inspect while revving.

glokul

Yep, that was the first one. The leak was very close to the connection at the head. Haven't seen any oil leaking there but now that I think about it, maybe 4 years ago, my 2000 DX had the same leak on the same hose which was causing overheating, which eventually lead me to replace the head gasket on that one.

Hoping not, but if so, I guess that will have to wait for an early Saturday morning start.

I'll check into that, thanks.

Thanks, that page is helpful. I will not be surprised if it's the gasket, don't think it's ever been changed.

Right, I was running the heater and it was blowing hot all week up until I switched out the thermostat, which might be telling. However, replacing the old one did not bring back the heat.

I did this, except I pulled off the upper radiator hose and pointed it into a container, revved the engine and nothing came out. Maybe there is no coolant left in the block? I will pour some coolant into the upper hose and hopefully that will find it's way to the pump.

I'll check back in later tonight with updates! Thanks for input

ezone

This could indicate an air pocket trapped in the high areas of the heater circuit. An air pocket can block the flow of liquid.
If you JUST replaced the thermostat then you probably need to bleed the trapped air out......



If you've had the heater hoses pop and the engine overheated, it may have blown the head gasket.....and if it is not a horribly large breach it can pass every test most people think to check -----mixing fluids, steam from exhaust, milkshake oil, block check, compression, it can pass every one of them.
No, no, no, no, no. Attach it and refill the radiator....leave the radiator cap off........you just watch the hole where the cap was for liquid flowing past it, that indicates circulation.

glokul

OK but with the valve to the heater core shut off, the coolant would just bypass it, correct? That is, if my pump is working, but, see below...

No coolant flowing at all out of the top radiator hose. This should be flowing at all times, correct?

ezone

I have no idea why the site is randomly ghosting (hiding) posts.
My reply was about your statement that you lost heater output after replacing the thermostat. I figured there could be an air pocket preventing proper liquid circulation through the heater core.

If a water pump cannot develop sufficient pressure and velocity to push an air pocket on through a circuit, air sometimes has to be bled out in other ways.

I guess it may depend on how low the level was inside the block. The pump may not create enough pressure to push liquid up and out of an open system, the system was designed to be closed. Especially at idle.....It might be able to build more pressure with high RPM though.


If the pump had no impeller at all, the engine would be spewing antifreeze in just a few minutes of run time as the liquid boils inside the cylinder head (assuming system is full) and pushes outward from expansion.

glokul

OK, well thanks for all the replies people, I'm thinking at this point will just have to be a side project. This was my second 6th gen and they both made it to at least 240K and seemed like they will both keep going. But, on to an 8th gen, those engine bays are very small! I hope they are as reliable as my previous civics