Hi people,

Made an account because I've been having some issues with my car. I currently have a 91 civic shuttle with a b16a2 swapped into it (out of 92-95 eg vti hatch).
The engine was using a lot of oil in the previous car it was in so I personally rebuilt it, and had some things done professionally.
After the rebuild and engine swap I've been having some overheating issues. The car will randomly overheat and send cooling fluid out of the little expansion box next to the radiator. After replacing the thermostat, the temp gauge started shooting up to max temperature randomly. It shoots up, stays up on max heat for about 2-3 seconds and then goes back to normal. It happens randomly, might happen about twice in a 15 minute drive, but sometimes doesn't happen for a while.
The fan on the radiator doesn't come on normally (but car still seems to overheat when it's on, wired it so it's always on now).
So far I have looked into the following:
- replaced the fan switch
- replaced the radiator
- replaced the thermostat thermostat.
- my ECT seems to work fine since VTEC is kicking in.
- the system isn't clogged, I've checked the hoses.
- no visible leaking while car runs idle
- no visible smoke out of the exhaust
- radiator fan works when I stick a paperclip into the fan switch plug

Myself, I am thinking I might have air in the system or it might be the radiator cap (didn't replace that yet). Since the engine is recently rebuild, I don't really think it can be that. Never had any issues in the car it was in before we swapped it in mine.
I will attempt to get air out of the cooling system by taking the radiator cap off and letting the engine idle for about 30 mins.

Since bleeding the system and replacing the radiator cap are the last idea's I have to try and fix the sudden overheat, it would be greatly appreciated if you guys could give me any tips or idea's for other issues that might be causing this.
I have been reading up on the issue all over the internet and plenty of forums, but nothing seems to be suiting exactly my issues.

Thanks in advance for the help!

 

sounds like air, and the coolant in your overflow is a bad rad cap
Unless there is something blown in the engine, pressureizing the coolant beyond the rad caps holding ability.

I reccommend renting a rad tester and looking for leaks.
If no leaks are found just bleed the coolant and get a new cap.

 

I'd ensure the coolant system is fully burped of air, put a new radiator cap on, and see how it does. If you still get overheating issues, do a compression and leakdown test to verify the status of the head gasket.

When you rebuilt the engine, did you have both the head and block resurfaced? New head gasket torqued in the proper sequence? Just asking...I've skimped on having the block resurfaced in the past and this has bitten me. A bad radiator cap can cause your engine to overheat as coolant bypasses the cap. If you overheat the engine enough, you can warp the head and blow the head gasket. If you then replace the radiator cap, you can still overheat because of the blown head gasket. The overheating then damages the spring in the new radiator cap, which causes it to fail in a matter of days or weeks. You can end up in this vicious cycle of trying to chase down the cause.

 

@acmoc hey, thanks for the reply. The radiator I bought is brand new, do you still think it is necessary to run leak tests on that?

@DaX thank you for the reply. It's been a while since the rebuild, but I am pretty sure I had both the head and the block resurfaced. Everything was torqued in the right order. I've had the car overheat a few times, but never really to the point that it was overheated for a long time. I guess if replacing the cap and bleeding the air out doesn't work, I will indeed have to look in the direction your pointing out. Just making sure I am not forgetting about some (minor) issue that might cause the problem. Thanks a lot for the help.

 

The machine looks like a small bike pump with a gauge, one end has adapters for radiators. It pressurizers the whole cooling system not just the radiator. You pressurize it to the oe spec (usually found on the rad cap)

With the engine off it's easier to find and hear a leak. The leaking area can also be suckin in air and creating air pockets.

 

did they vacuum test the block and head for cracks
and what are the compression numbers ?