I have a JDM B16a in my crx with what I estimate to be between 70-100k miles on it. It is cooled with a radiator from a 99 civic Si and accompanying fan. I've been driving it for a number of months now, prior to which it sat without running for somewhere between 7-10 years (in car, w/ oil & coolant).

Just recently I took it for an extended trip of 400mi to test its highway endurance and it has trouble keeping temperature after about 30 minutes of driving (up until then it's totally fine?).

I'm running out of ideas here so I thought I would ask the community for help.

Things I've tried:
New thermostat
radiator flush
checked fan wiring
bled coolant loop for air
running 50/50 coolant currently (non Honda, does it matter?)

I've also recently (in the last 4000 mi since I got the engine running) had the head rebuilt, new gaskets from the head and up, new fluids all around a few times over, etc.

I have not replaced the water pump but was told I probably shouldn't need to.

I apologize for the wordy opening post but I want to provide any info that may help.

 

Have you checked to see if your fan is working?

 

Fan's great.
It was actually connected to the a/c condenser fan plug for a while when I first got it (oops) but it turns out the engine fan is never on without the a/c fan so it worked exactly the same anyway.

 

I will mention that I have pretty short gearing (as a b16 is wont to do) and am at ~5000 rpm in 5th for a while before I start to have problems, but various stops and idling seem to have little effect on the time for the problem to show (even if it cools down to normal again)

 

Is it a full core or a half core? If its half make sure the empty space is blocked off or it can cause the air to go around the rad and not through it

 

Half size radiator. Do you mean a gap between the fan shroud and the radiator or the radiator and the body?

I eventually plan to get a full size performance radiator but I feel like this one should be enough since it was paired with a b16 from the factory.

 

Half core only fills half the space in the bumper opening. The other half (where the AC condenser usually is) is open allowing air to take the path of least resistance through that big gap.

I believe you have the condenser though, since you said you had the fan hooked up.


One other thing, you said that the radiator fan only turns on with the AC on, that should not be happening.

The fan on the radiator should run without the AC needing to be on.

 

No, I said the a/c fan will always turn on when the radiator fan turns on, which is normal since normally both fans are radiator fans too. I do have a condenser and fan for it too but o fixed all the wiring when I did the recent a/c install (no, the overheating isn't caused by a/c because it overheated on my trip to but a/c parts)

I also don't have a heat shield on my exhaust, but that shouldn't make a difference with radiator temps I don't think.

 

Owning a CRX with a b16 in it, I have no problem, however I run the stock si rad (full size). I also have an em1 and I am using the ex rad in it. I needed one on a sat and the local stores didn't have the si rad. You have to use the delsol hoses. The ex rad is a 4 core and the em1 rad is 2 core. I would suggest using the crx/civic rad. It lacks the half rad "cool" factor but it works well as well as the one in the hatch. It also has a b16 with the stock rad. I have never had a cooling issue ever, even in heavy stop and go traffic. Good Luck
Regards
Dave

 

I have always been told that when you run a half size you need a block off plate to force air through it, without the plate the air will seek the path of least resistance and mostly go around the radiator.

 

I'll look into the block off plate, but do you know of a way it can be set up to still work with a/c? I have an r134 system so I need the full condenser capacity, but I may be able to at least restrict the airflow on that side with a perforated plate or something.

 

You only run the block off if you DONT have the ac condensor. The ac condensor makes it so the whole frontal area has the same amount of wind resistance.

Since he does have ac, then his issue is being caused by something else.

Do NOT run the block off, as of is ONLY meant for non ac cars. Using it with ac will cause the ac to not work properly.

Honestly it sounds like the radiator needs to be replaced. Radiator flushes rarely work. Coolant turns acidic over time too (though maybe this only occurs in engines that mix iron blocks with aluminum heads?)

Maybe swap the water pump and timing belt. If it sat for that long then the belt is now garbage (rubber degrades over time, a brand new belt is garbage after 5+ years of storage)

 

You said you didn't replace the pump, it seems more like this is the culprit, since it's the last thing to replace.

 

I did the timing belt when I had the head and gasket done, but I've been told my numerous sources and my own research that a failing pump impeller should show symptoms at idle rather than high speed, not to mention the very adequate upper radiator hose pressure at idle.

With what little I've found about block off plates they typically come after the intercooler in turbo setups (car was once turbo, hence radiator) so it may still have an effect even with an a/c condenser, but I would have to devise one that still allows full condenser airflow.

Another source for a 99 si said a radiator cap could be at fault, and I think I have a spare, but I don't understand exactly how that could work aside from coolant boiling away.

 

When the radiator cap fails to hold pressure, the system loses cooling efficiency.

Have you noticed your coolant reserve being dry/low?

I recently had this issue on my stock CX where the cap was old and the reserve was overflowing and I was slowly losing coolant due to it coming out of the top of the tank. I've replaced the cap and so far it's stayed fine.

 

I was losing coolant before, but I attributed that to a few hoses I knew were weeping around the edges (detected with u/v dye). Don't think I ever overflowed the reservoir as a source of coolant loss, but I'm going to try another cap right now and see what it does.