john donovan

I have a 2004 civic that overheats so far I have tried thermostat,sensor ,radiator ,cooling fans working properly compression test is 155 across all 4 cylinders engine runs smooth no coolant in the oil ,no oil in the coolant leakdown test at 35 psi held for 20 minutes no white smoke at start up the only thing I haven't looked at is the water pump is it possible or am I missing something else any feedback would be greatly appreciated

Wankenstein

How long from cold start does it take to overheat? Does engine physically overheat (releasing pressure) or are you going by the dash gauge?
Did you test or replace the parts you mentioned?..please be specific.

Did you do a leakdown test: 100-150 psi in each cylinder at TDC and inspect for bubbles in coolant system with cap off radiator. OR are you referring to a coolant system pressure test? If, you are referring to a coolant system pressure test (leaks) then you shouldn't go above the psi listed on the radiator cap or sevice manual.

A pressure test can help to determine some types of head gasket breech... if there is breech that allows coolant into the cylinders. If the system is holding pressure then I'm not sure if 20 minutes would be long enough to force enough coolant into the cylinder(s) that you'd be able to remove spark plugs and see coolant on them. I've read info that some people test for head gasket breech by holding pressure for 24 hours but, again I can't confirm or deny that will work.

With Honda engines the typical head gasaket breech generally results in coolant loss in radiator and gain in the reservoir. Ezone's straight shop air 150 psi (no leakdown tester) at TDC, radiator cap open to inspect for bubbles is the best way to determine.

The best time to check for the possibility of abdnormal white smoke (coolant in cylinders) is at cold start in the morning. Have someone start the engine and occassionally rev engine while you watch and smell (from a few feet back) tail pipe emmissions.
Allowing the engine from operating temp to cool down overnight will draw coolant into the cylinders if there a specific type of breech or crack in cylinder head or block that will allow it to do so. A block test is inexpensive (free rental at parts store) $10 for test fluid and can help determine some (not all) types of head gasket failures.
Read on types of headgasket failures: http://www.agcoauto.com/content/news/p2_articleid/200

Easiest way to check the waterpump is to open the radiator cap at cold start and let it when the thermostat opens up (at or near operating temp) look inside the radiator neck to see if there is a flowing current. Rev the engine and hold the revs for 20 seconds or so to get the coolant flowing faster to make it easier to see movement. Should be flowing steady in one direction. A waterpump can partially fail as well and cause intermittent overheats. Partially failing means it will spin but not as fast as it's designed too at particular rpm's. I fully failed waterpump will often squeal or leak.

Is the heater inside the car working correctly at idle and while driving?

Other possibilities for overheating are:
low coolant level
air in coolant
clogged radiator
breeched head gasket
failed engine coolant temp (ECT) sending unit: if you are just basing on dash gauge

john donovan

thanks for your help and info on this megalodong the temp sensor and thermostat are new the radiator I replaced was used but I know for sure there were no issues with it the cars heating system is working fine it takes 45 min to an hour before it overheats the cooling fans come on and off like they should that is why I think it could possibly be the water pump I also pulled off some hoses to make sure circulation was ok

Wankenstein

Was it a leakdown or pressure test you performed?

Did you use an OEM/honda genuine thermostat?
A thermostat if fully closed will generally overheat in minutes but they can also fail by being stuck partially closed/open and can take longer to cause a system overheat.

Is the radiator cap new/OEM ? Do you know how many miles are on the waterpump?

Start by replacing radiator cap to OEM (if not already). Fill radiator up to top, fill reservoir to proper level. Put front of car up as high as possible on jackstands or park up hill. Set climate control to max heat, recirculate, with fan off. With radiaotor cap off bleed air out of coolant system..occassionally steady rev engine (2500 or so rpms) to help push air bubbles out. Do this for 15-20 minutes or fans come on twice at operating temp. Observe bubbles..may have medium sized bubbles initially while revving or if high revving..as bubbles get smaller check at idle for a few minutes and bubbles should be tiny or non-exisitent..end of bleed.

Do not let coolant level drop in radiator during bleed process..add distilled water as needed. After bleed is finished fill the reservoir full (to the top above fill fill level) and allow the engine to cool overnight. Next morning check both the radiator and reservoir levels..if resevoir is filled past "full level" line then use a turkey baister to remove excess.

During the bleed process look inside of radiator neck to see if waterpump is moving coolant swiiftly through radiator during revving. Everyday for the next week or two monitor the coolant level in radiator and reservoir closely. If coolant starts dropping in radiator it's via an external or internal leak. Place a piec of carboard under car for next few days to observe for external coolant leaks. Although, some small leaks never make it to the gorund as they burn off on a hot engine beforehand.
Can try coolant system pressure test for leaks with engine cold first and then at operating temp. Sometimes it requires climing under car with engine running to find coolant leaks..take much caution if you decide to do this or better yet..bring to a shop with a lift.

ezone

Head gasket.

Wankenstein

Lol..I wanted to summarize it that quickly but I figure a bleed is free and might provide a ray of hope

john donovan

well finally got the time to do the leakdown test and it is the head gasket on #3 cylinder so now I will check the head for warpage and repair it I bought this car for my grandson just got his licence car is in great condition with a new transmission so I have a few months to fix it new waterpump and timing belt he should be good to go thanks again for the information great site

john donovan

definitely the head gasket sent the head to the local engine rebuild shop and it was warped so now I know the cause of the overheat the head has been milled and ready just to find the time thanks again to all for the info