Have a 92 civic with the d15b7. I got the car for free with a blown motor so I replaced it. Same motor except it was from a 93 automatic. Been driving it for some time, probably put 800 or so miles on it but just recently it’s started getting really hot when I take it out on the highway. First thought was airflow to the radiator was restricted since it had only overheated on the highway. Nothing visibly blocking it, so I jump the cooling fan to run continuously, (temporarily) and nothing changed. Now I noticed that after it starts to get hot i pull over and the reservoir is way above full. Bad valve in the radiator cap? Nope. Brand new one, proper pressure, no change. When I put the new motor in, I did the timing belt and water pump, made sure the thermostat was working, and replaced upper and lower radiator hoses. The only thing I have not done (that I can think of) is pressure tested the system and replaced the hoses to the heater core. For the first few hundred miles I drove the car the temp gauge didn’t even work. No issues as far as I could tell. Just frustrating. Today I let it idle in the driveway for about an hour or so, no leaks, didn’t overheat at all, but the overflow tank filled up twice and I had to empty it. What could make it do this other than a bad cap? Any help is appreciated.

 

test coolant for exhaust gas, many parts stores will rent you one:

https://itstillruns.com/test-exhaust...t-7885485.html

 

Fairly certain it is not head gasket, yet I haven’t entirely ruled it out. I checked compression yesterday and I have 125 psi on all cylinders and none are abnormally clean like they would be if it is burning coolant.

 

125psi is really low. I'm suprised it's still running properly

 

125 is low but what is more important is that the psi is consistent with all cylinders.

Open the oil cap, is it milky on the bottom? A whiteish sludge?

Open the rad cap, is there little specks of oil in the radiator? Does the cap look milky?

Look at the middle of the block where the head gasket meets, is there seepage?

 

As far as I can tell, there are no signs of a blown head gasket. No water on the dipstick, no sludge in the cap or anything. I know 125 isn’t amazing for this engine but if it was a head gasket leak one or two cylinders would be down on compression. I also used a harbor freight compression tester, which I hear are notorious for low readings.

 

But you have a symptom, it’s overheating. Head gaskets can go without all the other symptoms and just overheat nothing else.

The only other thing I could say is to check your water pump or coolant leaks somewhere

 

Yeah, I’m thinking I might have caught it early. A compression leak into the cooling system would increase pressure and cause the issue with the coolant dumping into the overflow, too, right? I just brushed off head gasket being a possibility at first because my compression readings were all so consistent and I don’t see it smoking or anything.

 

Been reading some older forums, pretty confident it’s head gasket now. Honestly I will be relieved if that is the case, cause I can knock it out in a day and be done with it. Beats wrestling it with no results. I’m gonna go ahead and buy the kit. Thanks for the input guys

Also, are the head bolts on the d15b7 torque to yield or can I reuse the old ones?

 

Don't cheap out on some FelPro headgasket. Always get a Genuine Honda one

 

Oh yeah. Never cheap out on something as important as a head gasket.
One more thing:
The last time I drove the car, it was overheating worse than it ever had, to the point where I had to pull over, let it cool down and top off the radiator. I didn’t have time to trailer it, so I drove it the rest of the way home with the heat on and watched temp closely. Drove it about 30 miles or so going 55 on the highway. Temperature was fluctuating the whole time, holding between halfway and rising to or a little above 3/4 to HOT. I didn’t let it touch red. Should I worry about the head being warped? Ideally I wouldn’t have driven it overheating like that but didn’t have much of a choice.

 

A few things ..

(Make sure the cooling system is filled to spec. ) regular water is ok to use while trouble shooting,

How did you go about confirming the thermostat was good? Remove temporarily and re-check symptoms

Whats the condition of the radiator? open the drain valve and monitor coolant temp, (and that the cooling fan is properly cycling at idle) .(being careful to not burn yourself)

To help confirm faulty head gasket, check for excessive bubbles forming in the radiator and or pressure coming from the overflow hose.

-Post your end results or solution

 

OP, make sure to get a good 50/50 coolant to DISTILLED water ratio. Bleeding all the air out of the system is key. And make sure the radiator has no leaks and the cap is actually holding pressure. If' it's old and you're unsure, get a new one. They are like $12 brand new, Genuine Honda or course. The only aftermarket cap I would recommend is Stant.

 

To test the thermostat I just dropped it and boiling water and physically watched it fully open up.
Radiator is in good condition, first thing I inspected after it got hot the first time. No bent fins and no leaks, nothing blocking flow except some bugs.

 

Yes I learned how important it is to burp the system on a previous car. No air bubbles in here for sure. I’m pretty convinced that it is the head gasket as of right now. Cap is brand new. I ordered head gasket last night and I’m gonna install it as soon as it gets here.
But does anyone have any experience with these motors overheating? Do the heads warp easily? Should it be a simple R&R or am I gonna have to take the head in to get checked out and/or resurfaced?

 

Probably.
Do you know our temp sender is good?
How many miles on the engine?
W/ compression numbers like you posted I would send the head out to machine shop for flatness check and 3-angle valve job, check guides, replace seals.
Not sure what your objectives are for the car...

 

Temperature gauge in the dash and the sending unit came off a wrecked car I bought for the motor. Not 100% sure it works perfectly but it seemed accurate the first couple hundred miles I drove it. About 235k on the motor, and all I’m planning on doing with the car (with this motor in it anyways) is using it for a daily driver.

 

Its an aluminum block with an aluminum head.

It's hard to say yes or no to a warped head, you can use a straight edge like a metal ruler to test the head to see if its warped. If its warped there will be dips and gaps on the ruler across the head.

Usually a shop charges $85 to deck a head. Depending on the vehicle sometimes its just cheaper to swap it to a d16 out of a parted out car

Make sure you do a cooling system pressure test first. Ive had minor tear in a heater hose cause all sorts of problems and it would only leak while driving never while idling.

 

And what does the coolant flow look like in the radiator with the cap off, while engine is running? Smooth flow or bubbles?
Also, a better inspection of the radiator is proper flow through, bent fins or leaks could also be an issue of course, just not as severe as what youre describing.
I would ascertain coolant temperature is equal from upper to lower radiator ports, along with an exhaust gas test, as another member also suggested.
I wouldnt be so quick to start replacing parts until you have verified the problem. .

- Post your end results

 

I would at least have the head checked by a machine shop. My local shop will do a flatness check for free, and milling is $35. On my last blown HG I had good compression numbers and pretty good leak down numbers. My money is on it being a HG.

 

Went out there today, started the car, noticed an excessive amount of water was coming out of the exhaust. Gave it some throttle, and tons of water comes out of the tail pipe. I attached a video but I am on a phone and don’t know if it’ll go through or not. Anyways I know moisture and dripping out of the pipe is normal but that’s a crazy amount coming out of the exhaust.

 

Damnnn how long did you have it sitting for

 

Man I was driving it the other day lol

 

Update:
I pulled the head this afternoon, no real obvious spots in the head gasket where you could see it was distinctly blown. But I tore the gasket up real bad when lifting the head up so it’s hard to tell. One thing I saw that was concerning was a bunch of dirt and crud on the underside of the gasket, in the coolant sleeves. The car I got the motor from was in a front end collision and the radiator and hoses were busted so it was exposed. I remember when I pulled the motor there was a mud dauber nest in the upper coolant neck. I cleaned it out as best I could but I guess not good enough. My theory is that the dirt blocked flow in the block and caused it to overheat the couple times, which then caused the cylinder head to warp which is why I’m getting water out my exhaust pipe. I’m bringing the head in to a machine shop tomorrow and hopefully it’ll all be resolved when I get it back.

Kind of just looks like gasket material in the photo, but there was dirt and white crud all up in there.

 

Looks like scale - make sure you use distilled water when diluting your coolant. I would recommend going with an MLS head gasket instead of the fiber-metal one when you put it back together.