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Ok, so I'm stumped.. I had a blown head gasket.. Water going into overflow reservoir.. Overheating.. Etc. had the head machine and 0.009" milled off of it. I put a new water pump, timing belt, new radiator, OEM thermostat, aftermarket radiator cap. So my fans weren't coming on right.. So I jumped the switch just so the fans would stay on so I could drive around the block and check for leaks, etc. this joker started to overheat.. What could possibly be causing it to overheat.. I've pretty much rebuilt the top end. Only thing I haven't replaced is the ECT sensor and the fan cooling switch( which I know is bad, that's why I jumped it). Heeelp

 
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What did you see?

 
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I started to see my temp. gauge go up.. I let it sit at idle for a good 30min and it did just fine.. Not until I started driving the temperture shot up

 
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So it didn't puke antifreeze out or roll smoke out from under the hood....

Is the radiator and cooling system completely full, and burped of all trapped air?
Got coolant flow?

What does the heater do at this time? Does it blow hot or cold? Does it blow hot or cold while driving, and does it blow hot or cold when sitting still idling?

Is it pushing antifreeze out of the radiator and overfilling the reservoir?

What was the surface finish like when you got the machined head back from the machine shop? The surface is supposed to be as smooth as glass, not rough enough to hang a fingernail in. If it is too rough, it can leak even with a new head gasket.


FYI technically that was .001" too much. According to the manual .008" is the maximum resurfacing limit, but to be accurate the overall head height is supposed to be measured and accounted for..

 
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As a rule of thumb all piston-to-valve pocket clearances in production interference engines are supposed to be close to 0.060"... if Honda spec'd 0.008" while taking all engineering margins into account, that must be eating up a ton of vertical clearance. However I don't think it's the deck height that's causing the overheat.

Did you possibly put the t-stat in backwards (assuming this install isn't impossible to do by design... it happens in tons of cars). Obstructed flow only at higher rpm. I'm assuming that belt tension was properly done as well and there are no problems with the alt bracket bolts...

One way to check if coolant is flowing to the rad... is to feel it. If the hoses and core are only lukewarm when the gauge reads sky-high... ta-daaa.

On my (oh-so-problem-riddled former DD) Ford Escort, I swapped a timing belt and water pump, requiring the low rad hose to be disconnected (passed through the alt bracket ). I'd buttoned everything up and started it, ran it, all fine... job done. Woke up the next day to get some supplies for cleanup... when it stuttered to a halt in the middle of a major intersection. Luckily, I got it to catch just enough to get to the curb, popped hood... rad was nearly dry.

Turns out the lower rad hose had a pinpoint crack that only spewed out coolant in a mist, at op temp pressure. No mist when I checked it cold... and I went for at least twenty miles of testing after that, which is when it depleted itself. Moved the hose a bit further onto the rad spigot and reclamped... fixed. At least it wasn't a head gasket's pressurizing a coolant jacket and overpowering a stock rad cap, though. :P

 
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I didn't have the heater on full blast when i filled the radiator back up, but according to the book it holds 1.1 gal. I've got about that much in there. Is it that touchy? Just that little bit of air will cause it to overheat? The surface finish was like glass, I'm a machinist by trade.. They did good on that.

 
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1.1 doesn't SOUND like enough.
Had to look, FSM states 4.0 liters (1.06 gal) for a drain and fill, and 5.0 or 5.1 liters for an engine overhaul....which still doesn't sound like enough LOL.


These cooling systems run close to the limit of efficiency, no room for error. If the weather is warm they can run hot at only a quart low.


I fill the cooling system and run the engine through warmup and radiator fan cycling with the Heater valve wide open (temp selected HOT) but fan off. I also raise the front of the car to help move air pockets toward the radiator. Um, higher than this:



Can I send cylinder heads to you? The local machine shop here has no clue. Last head I sent out came back looking like the grooves in a vinyl record.

 
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Thanks a lot for your help! I'm going to go buy some more coolant from the dealership.. They don't give that stuff away, that's for sure!! Then I'm gonna park on the steep incline in my driveway and fill her up! I'll let you know how it goes.. Now with me bypassing the fan switch, that shouldn't hurt nothing, as long as my fans are running right? Both hoses are hot, so thermostat is working. Should I buy an OEM radiator cap? I bought a cheap aftermarket one.. Replace it?

 
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If you have the fans running all the time, you will shorten the lifespan of the fan motors. Other than that, you won't hurt it.


IF you had both fans running AND both the upper and lower radiator hoses are equally HOT, then the fans are not removing sufficient heat from the coolant in the radiator.
While the fans are running the bottom hose should not be as hot as the top hose. You have maybe 190*F from the engine going into the top of the radiator, fans are supposed to cool the liquid, then you should be able to discern some temperature drop as the coolant exits the radiator through the bottom rad hose.

So, were both hoses equally hot?

Is the radiator or condensor clogged with bugs and debris in the fins? How about the inside of the radiator core, cooling tubes limed up or have calcium from hard water deposits?





Got a scanner of any sort you can connect to read engine coolant temp data live from the computer?

 
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It's a brand new radiator. Both hoses were equally hot. I let it idle for about 30 minutes and felt both hoses. They were the same temperture. I dont have a scanner to read the temps. I'm just jumping that switch until I find my problem, then I'm going to buy a new fan switch.

 
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I'm wondering if you got the right type of cap... the OEM has that little puck in the center post (which IME anyway was the first time I'd seen one... but then again all of my vehicles except the bikes have been pre-'99). They don't interchange IIRC.

 
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My notes about aftermarket radiators tell me to stay away from Spectra, Murray, and CSF. Mostly due to cap fitment problems in the recent past.