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Integra aluminium radiator swap
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After chasing down worsening cooling issues on my new engine, I finally decided to replace the radiator (the only part that wasn't replaced during the rebuild). On George's advice I picked up a cheap 86-93 Aluminum Integra radiator on clearance. The dimensions are close to identical to the original prelude core. The upper and lower hose outlets are about the same size and in the same locations. Unfortunately the expansion outlet is on the opposite side of the filler - not a big deal. This is not a direct swap, and requires some modifications, namely mounting brackets to be fabricated. Fairly simple work, especially with a welder available.
I also installed some new electric fans which I got on sale two for the cost of one. These are driven off a new secondary relay triggered by the original relay which is triggered by a new 90C thermo switch (5C hysteresis) placed in a lower hose adapter. The second higher current relay was needed as these fans are a lot more powerful than the originals and I melted the honda relay on my first wiring attempt.
New Parts:
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Out with the old:
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Comparison (massive weight reduction!!!):
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In with new:
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We need to make a bracket to sit across here. The new bracket bolts into the existing perches where the oem radiator pegs sit. The 90deg angles keep it sitting horizontal. The new radiator pegs are spaced further in-board, hence why the new bracket is required.
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Everything ready to install:
(pro tip:- when mounting the fans, throw away the included pull-through ties, and just use cable ties for greater reliability)
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From Above:
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From Underneath:
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Needed a few mm of extra clearance. If I was more patient, I may have been able to lower the bracket position, but at this stage I just wanted to finish the job, so cut a little hole in the bonnet webbing. Already had a hole cut for my weber throttle linkage so didn't care about making another:
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I modified some ally civic radiator stays for the top brackets. These fit almost perfectly to some existing holes on the car panel.
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They just need a little twist to suit the angles!
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Finished!
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All done, I hope you enjoyed. I just need to get a longer expansion bottle hose and I will run it along the front of the radiator so it is hidden.
Oh by the way...
Lower hose thermo switch adapter, because the integra radiator doesn't have a thermo switch bung.
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Relay gets power straight off the fuse box:
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Temperature now stays pegged to the middle of the gauge at all times. This is with a 180F high flow thermostat, no fans needed unless it is particularly hot outside and in stop-go traffic so they do occasionally flip on.
Result: No more cooling issues, and ready for the harsh Australian summer!!!
I also installed some new electric fans which I got on sale two for the cost of one. These are driven off a new secondary relay triggered by the original relay which is triggered by a new 90C thermo switch (5C hysteresis) placed in a lower hose adapter. The second higher current relay was needed as these fans are a lot more powerful than the originals and I melted the honda relay on my first wiring attempt.
New Parts:
Out with the old:
Comparison (massive weight reduction!!!):
In with new:
We need to make a bracket to sit across here. The new bracket bolts into the existing perches where the oem radiator pegs sit. The 90deg angles keep it sitting horizontal. The new radiator pegs are spaced further in-board, hence why the new bracket is required.
Everything ready to install:
(pro tip:- when mounting the fans, throw away the included pull-through ties, and just use cable ties for greater reliability)
From Above:
From Underneath:
Needed a few mm of extra clearance. If I was more patient, I may have been able to lower the bracket position, but at this stage I just wanted to finish the job, so cut a little hole in the bonnet webbing. Already had a hole cut for my weber throttle linkage so didn't care about making another:
I modified some ally civic radiator stays for the top brackets. These fit almost perfectly to some existing holes on the car panel.
They just need a little twist to suit the angles!
Finished!
All done, I hope you enjoyed. I just need to get a longer expansion bottle hose and I will run it along the front of the radiator so it is hidden.
Oh by the way...
Lower hose thermo switch adapter, because the integra radiator doesn't have a thermo switch bung.
Relay gets power straight off the fuse box:
Temperature now stays pegged to the middle of the gauge at all times. This is with a 180F high flow thermostat, no fans needed unless it is particularly hot outside and in stop-go traffic so they do occasionally flip on.
Result: No more cooling issues, and ready for the harsh Australian summer!!!
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100 Posts
Thanks for the excellent write-up.
Question, could you have installed the entire radiator a touch lower to avoid cutting your webbing?
I reckon that Civic radiators have similar vertical dimensions?
Do you think that was the car's original radiator? If it was that's amazing it survived 30 years in Australia. My 87 has it's original radiator, which is amazing these days as most new cars seem to puke their radiators in 5-7 years. My wife has a 2005 Saabaru and I have a 2007 Nissan Titan, both have problems with their radiators and other various things like leaking plastic parts. No such issues with the Prelude!
Question, could you have installed the entire radiator a touch lower to avoid cutting your webbing?
I reckon that Civic radiators have similar vertical dimensions?
Do you think that was the car's original radiator? If it was that's amazing it survived 30 years in Australia. My 87 has it's original radiator, which is amazing these days as most new cars seem to puke their radiators in 5-7 years. My wife has a 2005 Saabaru and I have a 2007 Nissan Titan, both have problems with their radiators and other various things like leaking plastic parts. No such issues with the Prelude!
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3,180 Posts
Thanks mate, to be honest it would have been possible, however there is only scope to lower an order of mm's before the edges of lower radiator tank foul the original brackets on each side. There is more scope to move it further back towards the engine which will also result in clearance due to the curve in the hood. The original prelude radiator has a gooseneck filler that kinks back towards the engine to over come this issue. I tried tilting the radiator back towards the engine from where I mounted it and judging by laying under the car, I could tell it resulted in okay buy marginal clearance, we're talking maybe half a cm here but probably okay. I just decided I wanted it to be vertical, further away from my hot extractors and I didn't want to do any more significant work to the bracket I had made. So basically yes, it would be possible to not cut the webbing with some more planning and effort.
To your other question, I suspect it is the original radiator!!! Full of rust, Copper was all green and flaky. Thing had a bunch of brazed leak repairs visible. I can't believe it was still hanging on. The extra heat from the new engine just pushed it past its limits, and I think my efforts to flush it made it worse by lodging all the loose oxide even deeper. At first it would only overheat on hot days over 30c when I was in traffic. Then it just started getting worse quickly, apparently inversly proportional to my efforts to fix it (fluid, flush, tstat, hardwire fans)!
To your other question, I suspect it is the original radiator!!! Full of rust, Copper was all green and flaky. Thing had a bunch of brazed leak repairs visible. I can't believe it was still hanging on. The extra heat from the new engine just pushed it past its limits, and I think my efforts to flush it made it worse by lodging all the loose oxide even deeper. At first it would only overheat on hot days over 30c when I was in traffic. Then it just started getting worse quickly, apparently inversly proportional to my efforts to fix it (fluid, flush, tstat, hardwire fans)!
Radiator
The other option is to have the original radiator re cored with a larger copper core but this is only an option if the top and bottom tanks and the side mounts are in good shape.
But it's good to see other options too in theory a higher peformance Radiator could be sourced and fitted in reality anything can be fitted if you have the skills and equipment.
I do like the fact you have two large fans instead of one and a small one should cope well on track day etc.
The other option is to have the original radiator re cored with a larger copper core but this is only an option if the top and bottom tanks and the side mounts are in good shape.
But it's good to see other options too in theory a higher peformance Radiator could be sourced and fitted in reality anything can be fitted if you have the skills and equipment.
I do like the fact you have two large fans instead of one and a small one should cope well on track day etc.
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Thanks. Yes the slim electric fans are a lot smaller and lighter.. Under normal circumstances, only one is really needed. They move a LOT more air than stock. I am now running them togeyher in series so that each is only half thr speed/power drain. This is still way more than adequate but probably achieves more even air flow through the rad rather than only having one. The ally radiator is maybe half the weight of the copper one.
I got quotes on a recore ranging from $300 to $400, but my tank hose inlets were rusting off anyway. No new prelude radiators available in Australia. I found this teg radiator for only $80. The two fans were $80 together. So in the end I think I got a lot more result for less than half the cost of a recore.
Yep, anything is possible with time and effort.
I got quotes on a recore ranging from $300 to $400, but my tank hose inlets were rusting off anyway. No new prelude radiators available in Australia. I found this teg radiator for only $80. The two fans were $80 together. So in the end I think I got a lot more result for less than half the cost of a recore.
Yep, anything is possible with time and effort.
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Well done Hayden! The radiator looks like its factory especially those brackets.
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Fair enough. I wasn't well equipped to weld the chassis. Only had a stick welder available. Could possibly have drilled and bolted I guess but the AC condensor is in the way and there's not really much chassis to work with in the middle area, just AC condensor, maybe a thin strip underneath it but not sure. Your suggestion if possible would certainly be better but II think my approach was the easiest I could see.
Weight reduction
Anyone would have thought it was me moaning about the weight! lol!
Could have used Ally bar to reduce weight hehe!
Looks good though and works that's the main thing! Hows it running now it's cooler? still got the oil burning out the top and sticking you out the cabin issue? or is that solved now?
Anyone would have thought it was me moaning about the weight! lol!
Could have used Ally bar to reduce weight hehe!
Looks good though and works that's the main thing! Hows it running now it's cooler? still got the oil burning out the top and sticking you out the cabin issue? or is that solved now?
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It does still emit a bit of vapour out the top, primarily when its been idling on hot days.
I've done some work on establishing a new pcv system through an eBay vacuum manifold. I just got a set of vacuum barbs and a tap so I'll be able to tap all four intake manifold runners. I'm aiming to finish sh that off this weekend. I'll post up in the pcvthread when its done.
Did some major panel work/ rust repairs last weekend, got inside the internal skins around from quater panels at the windscreen corners, so need to finish off some por15 and seam sealing on that job too.
In terms available of the tune I think I need to get a leaner pump charge. At the moment I have 0 bleed off so if I weaken the charge I'll weaken the main too so might leave it til I go back to the tuner although I did want to lean off the main around the peak VE anyway, and I think there's more power to be had now I've fixed the exhaust collector. Will be good to see the difference and then play with valve and spark timing on the dyno! Next big job will be the cold air intake.
Come to think of it, I have not experienced the same degree of engine-bay-heat-soak torque loss after the new radiator!
I've done some work on establishing a new pcv system through an eBay vacuum manifold. I just got a set of vacuum barbs and a tap so I'll be able to tap all four intake manifold runners. I'm aiming to finish sh that off this weekend. I'll post up in the pcvthread when its done.
Did some major panel work/ rust repairs last weekend, got inside the internal skins around from quater panels at the windscreen corners, so need to finish off some por15 and seam sealing on that job too.
In terms available of the tune I think I need to get a leaner pump charge. At the moment I have 0 bleed off so if I weaken the charge I'll weaken the main too so might leave it til I go back to the tuner although I did want to lean off the main around the peak VE anyway, and I think there's more power to be had now I've fixed the exhaust collector. Will be good to see the difference and then play with valve and spark timing on the dyno! Next big job will be the cold air intake.
Come to think of it, I have not experienced the same degree of engine-bay-heat-soak torque loss after the new radiator!
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Hey Smeado its been too long mate what's happening with your Lude, you should post us an update! I never did do the big valves unfortunately maybe next time the head comes off!
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Fair enough
I am so spoiled with my MIG but then I have yet to do any actual welding on my car. Aside from the crooked shifter but damn I could use a better (blingy) radiator lolNice work though! You can hardly tell its not stock.
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You should come to Australia for a holiday H. I'll put you up in return for lude activities lol
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Funny how I actually had a plan to do just that lol. I told Z about this a while back but idk if I'm able to do it with the budget issues and all. I'm always broke!!
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Save those pennies my friend.
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Not sure what thread the prelude switches are. There are more than one variant. The adapter I bought took m16*1.5 so I just bought a generic T switch to suit.
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