Now that it's getting hot out, I've been running into issues with overheating. My current cooling setup is a eBay aluminum radiator with a whopping 57mm core, two 12 inch SiliconeIntakes fans (no shroud), coolant reroute, and no undertray. I already have an LRB undertray that I have yet to cut to fit my intercooler pipes and install. Temps seem shoot up to >230f after a fair bit of heatsoak (20ish minutes of street driving) but stay at a relatively stable albeit slightly high temp (205-206) at idle with the fans on. I am looking at a variety of options to increase cooling capacity and am curious about which one will have the biggest impact:

1. FM, Koyo, or Mishimoto Crossflow Radiator (instinct tells me to go with FM)
2. Upgraded fans + shroud (FM most likely)
3. Or Singular Hood vents

Fans will only really help with low speed or idle conditions, which I don't have too much trouble with. Hood vents might make a significant difference, especially with the undertray installed. Instinct tells me that the radiator is the best choice, but downgrading to a much thinner core while upgrading to a crossflow doesn't make too much sense, and eBay radiators tend to get acceptable reviews from most people. Any advice?

 

Something isn't right.

Unless you live on Venus, 20 minutes on the street shouldn't be causing overheating in a vehicle with a large aluminum radiator and a coolant reroute, assuming it was competently installed.

(I'll assume that you remembered to remove the radiator from the box it came in prior to installing it, and that your cooling system contains some kind of water-like fluid.)

For starters, what instrument are you using to measure engine temperature? Is it trustworthy?

 

New stock coolant temp sensor for measurements. 100% sure it’s calibrated correctly, also have oil temp sensor which hovers between 200-220. It’s probably a 90/10 mix of distilled water and coolant. I just topped it off after driving and it took another quarter of a gallon, so maybe I had significant amounts of air pockets in the system. Will report back after a drive this afternoon.

Ive never seen coolant temps get this high on the car before, but I haven’t been in higher temps like this with the new turbo kit yet. Specifically, my new turbo is water cooled whereas my old one was not. I figured my cooling system was adequate up until the past few days.

 

My old DIY kit with the large ebay rad used to run similar (but slightly lower) temps, and I would easily see 230 if I pushed the car at all. I haven't installed my hood vents or shroud yet on the new setup, but installing the LRB undertray and trying to seal up the ducting helped bring down temps significantly back 2 years ago.

If you don't have one, Id recommends grabbing a coolant funnel like this to fill the rad. Makes getting air out of the system a breeze and prevents the mess.

Coolant Fill Tool

 

Agree you have a problem. Probably self induced.
On the street at normal speeds "any" junk radiator will have plenty of capacity. Oil temp reflects that you're obviously not creating excessive heat.
Are you sure your fan is spinning the correct direction? Above 30 MPH you don't even need a fan if properly ducted.
Are you sure you've purged all the air?
Undertray is hugely important. Airflow is everything.

 

A thicker core causes more flow resistance. If there is not enough pressure to overcome this resistance the thicker core rad is going to cool worse than a thinner one. Thicker is not always better.

If a miata with the stock core has problems overheating without the undertray, and they do, a miata with a more restrictive core is going to have all the more problems.

 

Where are you located?

 

Iowa, not the best place to try and tune. It’s frequently below freezing in the winter and we see 100+ degree temps in the summer on occasion with high 80s-90s regularly. Lot of temperature ranges to deal with.

 

Update: after topping off the radiator with water I went for a long interstate drive as well as some street driving and even got some nice stop-and-go action behind a hog semi. Temps on the interstate hovered around 225 but shot up to 235 on any medium-heavy acceleration - I did not try to push it any further than this. Street driving was more sporadic as temps seem to pull down while the fans are on at low speeds or at idle but heat back up while driving. Overall temps were a little bit lower on the street, 215-225.

I still think these numbers are too high, definitely out of my comfort zone considering it was only an 83 degree day. 95+ degree weather might make the car undriveable. I still need to either find out why my cooling system is being so inefficient or just upgrade it entirely.

as many have mentioned, it sounds like the addition of my LRB Undertray and some work on sealing and ducting the front end. I’ll report back as soon as I’ve done this with new temps!

 

It's because some ******* moron didn't put the undertray on, and rather than doing so they go about overheating the car and planning on spending money on other **** for no apparent reason.

/thread

 

How do you burp your car's coolant system?

Also the silicone intake fans suck just FYI. No low profile fans move more air then stock fans until you start buying expensive SPAL fans.

 

I wasn’t aware that the Undertray would have the drastic affect you and many others have claimed. I was also not planning on buying anything else, simply asking if it was necessary and what the best route to go would be. I appreciate the sentiment though.

 

lifted the front end up a good 18 inches, filled, and ran. Drove it then repeated.

 

Ducting ducting ducting.

If there is a hole for the air to go around the radiator it is going to. You have to make sure it's forced through.

Those fans suck.

What reroute do you have and is it installed properly?

 

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It's definitely the ducting. All of the air is simply going underneath and around the sides of the radiator.

 

You said in the first post you don't have an under tray so you have no ducting? Well there's your problem.