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Ej Frankenmotor brat swap over heating


SubieBrat
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About a year ago I swapped my 85 brat with a Frankenmotor 25/22 and 96 legacy harness. About two months ago i was driving around a parking lot with my friend and it started overheating. As soon as i started moving its cooled off. I dont have a problem as long as i don't sit still or drive a slow speed for more than about 5 minutes. Most recently it did it friday night when i took my girlfriend up a mountain road and we pulled over so we could look at the view. I left the car running for about 5 minutes and it started smelling hot, but yet again cooled down when i started moving again.

 

I have one 10 inch Hayden fan hardwired so its always on with ignition.

Modified brat radiator

leaks from the coolant cap a little. replaced the cap twice once with a used one in good shape and today with a new one.

problem started in august. i dont really want to add a second fan at this moment if i dont have to. pressure test holds extremely well

 

Any suggestions?

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  • 2 weeks later...

If the engine cools while moving but not at idle, and it's not the fans like Gloyale stated, it might be clogged radiator fins. If you live in, or drive through constantly dusty roads or live in the desert, go offroading a LOT, or drive FAST down a long gravel road, the dirt/dust will start coating the exterior radiator fins. Over time, it can completely block air flow.

 

Try this:

 

Take a garden hose, remove the nozzle sprayer so water is coming straight out. Hold it up to the radiator fins starting at the top in one corner (careful as the hose end will scratch/bend the fins if it touches) and just hold it there. You'll see really dirty water come out the other side of the radiator. That's the impacted dirt. Hold in place until water flow is CLEAR on other side. Do this for every row, ESPECIALLY in the corners and up top. Do NOT use a high pressure spray as it will destroy the aluminum fins. Should do this about once a year. In high dust areas, 2-4 times a year might be better.

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I think I would have to agree with Gloyale that it is probably a fan problem. When you are moving you provide air movement over the radiator fins to cool the motor ( the fans do absolutely no good over about 30 MPH ) and this is what the fans should provide when you are sitting at idle.  I have seen clogged fins but usually this manifests as overheating at all speeds.

 

Check first that the fan(s) are coming on at idle or if they are wired constant that they actually come up to speed. As Gloyale said the fan should be wired through a relay to get full power from the battery. You might check the output from the alternator or check for a weak battery.

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Clogged fins can happen just like it was described. At idle, the fan won't be enough to keep cool as the dirt will hold too much heat in, plus whatever the fan can't breathe through. Once moving, the air on, through patches, or getting around the radiator will be enough to bring the temps down.

 

 

I drove semis for about a decade. I had one that started getting hot at idle, but it'd cool once moving. They have mechanical fans that are huge. Called the boss to let him know and he was like "when you bring back, come find me in the shop". He had me pull up, and we did the thing with the water hose. Sure enough, dark, dirty water spilled out of every inch of the fins. Once all that was changed to clean water coming out the other side, it quit overheating. I understand the skepticism, but's based on fact. Also, a semi radiator is about the size of a Legacy hood and is around 3" to 4" thick. The fact something that big was overheating from dust in the rows was a feat in and of itself.

 

 

FWIW, salt and road dust are just as bad. And intercoolers can suffer the same issues. People think because they drive in the rain the fins will be "clean", but it's untrue for the most part, especially if you drive in heavily dusted areas or construction sites. 

Edited by Bushwick
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... perhaps head gasket leakage should also be ruled out as a cause...

 

 

I was thinking about head gaskets also,

 

especially after reading this:

 

...leaks from the coolant cap a little...

 

But, also he wrote this:

 

...pressure test holds extremely well...

 

So, I believe the issue might be caused by a mix of this two:

 

weak fan and clogged radiator internal passages.

 

Worth do a Radiator Cleansing, and if that doesn't help,

 

then a second fan or at least a fan rewiring could help.

 

Kind Regards.

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  • 2 weeks later...

Thank you for the help everyone. i pulled the motor and transmission out of the one that was overheating and put it all in my lifted one. It has a different radiator in it and i bought two new fans for it, both wired to work on the factory EA thermal switch, since the one on this radiator works. stays cool now actually drove the lifted one for the first time tonight and not a single problem.

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  • 3 weeks later...

I have some I just need to put them up. I was having some problems trying to upload them. I might put the in google drive. but I have a thread with the two last year. white one in no officially dead. just need to finish parting it and the my lifted one is getting the rear quarter panel replaced and wheel wells widened, then painted so itll probably be a week or two. and now I don't know how to link it. ill get something up pretty soon though

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