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Discussion Starter · #1 ·
I had a slight leak in my factory radiator so I went ahead and put in a Pro Alloy single pass unit along with top mount fans. I had read some comments that the top mount fans would reduce A/C performance but others had said it made no difference so I took the gamble. After putting everything back together and bleeding the system, I've been driving around for a couple months and I can now say for certain that I have higher coolant temps as well as poorer A/C performance.

Prior to radiator replacement, my Elise would typically sit at 178-182F coolant temp with the A/C off and moving at speed. This would go up to 184-187 when the A/C was on. Now, I'm seeing 186-192F when cruising steady with the A/C. If I'm driving at lower neighborhood speeds, I've seen 197-210F. The radiator is hot on both sides and all bleed screws spray solid coolant when opened.

I used to get 5 minutes of fantastic A/C performance until the thermostat opened and hot radiator exit air made its way into the climate distribution compartment. I actually had a compliment from someone of how cold the A/C (initially) blew. Now, it's just OK while the car is warming up which drops to poor when it gets heated by the coolant. Note: I performed the heater core bypass and insulated the climate compartment while the clam was off so it should be better than before.

I have noticed that my fans have not come on at high speed due to A/C pressure like they would before. It's possible I have a small refrigerant leak (although I've owned the car for 2 years and A/C performance had not changed) or maybe moving things around during radiator install caused me to lose some refrigerant (also seems unlikely). Even if this is causing the A/C performance drop, there's no questioning higher coolant temperatures. The fans sit so tightly under the radiator shroud that it seems like they block more air than they move and half of the fan is covered by the shroud so air doesn't have a straight escape path. I suspect a decent amount of air from the front half of the fans is being recirculated back forward. Maybe Lotus was right about pusher fans.

Does anyone have comments or suggestions on what to do next or can collaborate my comments? I haven't gotten stuck in traffic long enough to see how high the temps rise and the 210F referenced earlier was pulling into my driveway today after a couple miles of 20-30 mph roads.
 

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You mention that you've only been observing any changes for the last couple months - here in NC it has been hot as balls for the last couple months and was cool before then. Could it be environmental to some degree?

The fans not kicking on when AC is on is a huge indicator that something somewhere is not correct. Fix that first, and that may tell you all you need to know.
 

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Discussion Starter · #3 ·
The low speed fans kick in as soon as I turn on the A/C, I just haven't seen it kick over to high speed like I did for the past 2 summers.
 

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Discussion Starter · #4 ·
I went out for another test. Drove around for 20 minutes and got back to my driveway with the coolant temp at 203F and the A/C barely staying cool. I let it idle with A/C on and fan set to high and it made it up to 209F. At this point, the A/C was basically useless. I then revved a few times to raise coolant temps and check the high speed fan relay. At 217F, the fans clicked over to high speed and they had no problem holding/lowering temps from there. The A/C got marginally better with more airflow and I went for a drive around the block where temps went back down under 210F. One other thing I finally noticed is that I don't have a puddle of condensation below the car so the A/C issue is definitely pointing to low refrigerant charge.

Now I'm still baffled at why coolant temps are higher with the new radiator and fans. At least I know they can hold temps at idle in this 90 degree day.
 

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It seems like you have two interrelated issues. First being the fans. On my 2005 Elise, both fans kick on at low speed fans (both fans) when my coolant temp exceeds 200 F. I can't recall where past 200 but it's somewhere between 200 and 210 F. Also, on when I turn on my A/C, regardless of what my coolant temp is at, both fans turn on at high speed. So if my coolant temp is at 180 F and I turn on my A/C, both fans will turn on at high speed.

As for your high coolant temp when the fans are at high speed...this is NOT normal. My bet is that: 1) you are slightly low on coolant, and/or 2) you still have air pockets in your coolant lines since you replaced your radiator. So you I recommend trying the following:

1) Check your coolant overflow tank. If it looks slightly low or right about at the minimal level, add more coolant into the reservoir to the high mark. Let the car warm up to 180F, and then drive around for 15 minutes. Freeway driving may be better. If it creeps up and past 200 F, then drive back home and check the coolant level. If it dropped and near the min level, then you will need to add more coolant as air is still bleeding through your coolant line which is why the coolant level is dropping. But do NOT...I say DO NOT try to add more coolant when your coolant is hot. I know this is obvious, but just putting this disclosure out there.

2) use an Airlift tool (or similar) and try bleeding the air out of your lines. Note if you do this, you still need to check your coolant tank level as I noted above. Here's a link to an Airlift tool that I have used that worked well for me. Amazon.com: UView 550500 Airlift II Economy Cooling System Refiller: Automotive

I hope the above info helps. Keep us posted!
 

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Discussion Starter · #6 ·
My fan operates as you describe except for the A/C part. Even prior to replacing the radiator, the fans would never come on full blast due to A/C pressure unless it was very hot outside. Maybe the pressure was always a little low. The manual states the fans come on half speed at 208F and full speed at 217F, and they come on half speed whenever the A/C is running. It says high A/C pressures will also trip the high speed fans. I read an older thread where somebody mentioned he knew it was time to recharge his A/C when his high speed fan stoped turning on when the A/C was running so that aligns with your comment. I'm going to get a manifold gauge set and check the refrigerant pressures.

As for your 2nd comment, I'm quite confident my cooling system is fully bled. I initially had trouble bleeding the system and had the dreaded cold radiator hoses but it finally built pressure and started flowing. I have driven dozens of times for 30-45 minutes at highway speeds and the coolant temp does drop at highway speeds (188-192F). The heater works fine, the radiator is hot, and the bleed ports (radiator, hose above gearbox, and expansion tank) flow solid coolant. I slightly overfilled my expansion tank when bleeding it and the level has not dropped. I'm simply left thinking the Pro Alloy radiator and top mount fans are not as efficient as the stock radiator and stock fans :unsure:
 

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Discussion Starter · #7 ·
Time for an update...
I finally had some time to check the refrigerant pressure and it was low. At idle, low side was only around 20psi and high side was under 150psi. I ended up adding around 5oz of r134a to get them up to the correct values. Now my A/C works much better and the high speed fans run regularly. This helps control coolant temp a little more but they are still over 200F when moving at neighborhood speeds and over 190F when cruising at 60mph when ambient temps are in the low 90's. They were still better with the stock rad and fans.
 

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There's a reason that Lotus put the fans on the bottom as pushers. The pullers that are normally installed have two things going against them: 1) their of a lower CFM than the pushers 2) without a proper shroud, pullers don't work all that well. No reason to deviate from OE as far as I can tell.
 

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Discussion Starter · #9 ·
That's an interesting concept but seems to be opposite the general consensus that pullers are more efficient than pushers (all else being equal). The argument against pushers is that you have a big fan motor blocking some of your radiator. I wonder if the positive pressure in the plenum while moving negates this and forces air into areas that are normally blocked by the fan. I suspect it may also have something to do with the fact that the pullers are mounted so close to and get partially covered by the shroud, half of the air doesn't have a good exit path and gets recirculated to the forward part of the radiator. With pusher fans, there's a couple inches of gap between radiator and shroud that allow more clean airflow out.

It's not bad enough that I'm ready to pull the clam again to get the pullers off and swap back to pushers but I'll keep an eye on it.
 

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I've had puller fans on my Exige S for almost a decade. They were installed by Allen of VSA Motorsports and have always worked well. My AC actually was better after the installation. I do have a Laminova setup with an aftermarket radiator, but I've never had any issues.

San
 

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That's an interesting concept but seems to be opposite the general consensus that pullers are more efficient than pushers (all else being equal). The argument against pushers is that you have a big fan motor blocking some of your radiator. I wonder if the positive pressure in the plenum while moving negates this and forces air into areas that are normally blocked by the fan. I suspect it may also have something to do with the fact that the pullers are mounted so close to and get partially covered by the shroud, half of the air doesn't have a good exit path and gets recirculated to the forward part of the radiator. With pusher fans, there's a couple inches of gap between radiator and shroud that allow more clean airflow out.

It's not bad enough that I'm ready to pull the clam again to get the pullers off and swap back to pushers but I'll keep an eye on it.
No fluid - air or otherwise - likes to be pulled. Pulling is limited to a pressure difference of one atmosphere, max, and that assumes you've been able to achieve a pure vacuum. Pushing, on the other hand, is not subject to the same limit and is able to generate a greater pressure differential and therefore greater flow.Air can also get really nasty on the low pressure side of a puller fan well before it gets near a vacuum - think of a stalled wing.

Regarding the fans being "in the way", that matters whether or not they are in the front or the back. Air won't move well into something it can't leave, so blocking on the backside reduces flow just about the same as on the front side.

Now, making sure that air goes where you want is critical either way. I recently went through and filled those gaps you are referring to and contoured a lot of the ducting to reduce airflow that bypasses the radiator.

That all being said, have you ruled out a bad coolant bleed? I partially contribute my hassles to my heater core bypass plumbing, but I never can get mine to be fully bled until about the 5th try, even with a pressure bleeder.
 

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Yes, the consensus is that a puller is more efficient but I think it's a matter of packaging on the Elise. There is simply more room on the underside of the radiator/condenser sandwich. This extra room allows for the use of a larger diameter pair of fans than if mounted on the top = more CFM and more coverage. It doesn't help that the top half of the fans are shrouded by the body on the top mount situation either.
 

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Discussion Starter · #13 ·
Getting back to basics... I ran some part numbers and I think the most simple explanation is that the pullers simply don't move as much air. I had always thought that the relocation was to utilize larger fans but here it is in plain sight:

Stock:
Spal VA11-AP7/C-57S
844cfm
10"

Pro Alloy puller kit:
Spal VA07-AP7/C-31A
596cfm
9"

Combine these numbers with the fact that there is so little clearance above the puller fans that much of the air doesn't have an easy way to escape, and you end up with higher operating temperatures. The extra blockage might also be why I'm seeing higher temps while cruising. More blockage at the inlet in the pressurized plenum has less affect than blockage on the already constricted outlet.

Fortunately, the high speed fans have been able to prevent overheating but that's when they click on at 217F. The low speed fan only slows down the temperature climb. I don't normally sit in traffic in the Elise so this is less of a concern but I will probably switch back to stock fans sometime in the future.
 
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