Help - my car is running too cold
 

Due to heating problems I'd change my rad to a PWR rad and installed M-tuned's coolant reroute this summer. The new set up gave me great improvement and the former heating problems were gone (as long as I speak of coolant temperature since I still suffer from high IAT). On track this summer I had stable coolant temperatures a touch over 88 F.

But that was when we had nice summer temperatures. Now it’s getting colder and in temperatures around 37-40 F I face a new problem: I can't get my coolant temp to stay over 158-160 F when cruising. And it takes close to an eternity to get the engine warm (even with the heater turned off).

I have a 180 F T-stat that is working just fine.
Coolant/Water mixture aprox 50/50.

Anyone experienced similar problems? I was pretty sure that the t-stat was stuck open but it was working just great. Mayby I have to try to cover the rad. Any other suggestions?

Thanks!

Andreas

What is the diameter of the orifice that feeds your heater core?
-G-

Hi Greg!

Thanks for helping me out here. I hope I understood your question right here...

From the reroute adapter at the rear of the engine the oe hose runs to the heater core.

The t-stat has an orifice that my former 160 F t-stat didn't have. I’m not sure of the diameter though. But it's a tiny one...


Andreas

That little bypass on the thermostat shouldn't be an issue. I'd say double check that the thermostat isn't stuck open, and then count your blessings that you're not overheating and put some duct tape over the radiator.

I am having a problem with temps running too low as well. I have my fan on a switch, and I do not run it when I am cruising. If the car is not moving for very long the temps start to go up. The down side is, when the fan is on a switch, it is easy to forget to turn it on when the car is sitting and engine is running.

Cover half the rad, it's pretty simple

Paul has a problem with the Machine running too cool in the winter. He places a piece of plastic to cover like 1/3 of the radiator (maybe 1/2) and then he has no problems with temps.

I also put a blocker over the radiator. However, that's not enough, so now I'm wedging cardboard over 2/3 of the mouth. I'm jumping a lot more water past the thermostat than most though.

You never changed where the heater core outlets to, have you?

wat?

I'm wondering if he moved the heater core return to the upper radiator hose and not the lower.

If you route the heater core return to the top of the radiator instead of the bottom, you will have cold temp problems in cooler weather.

Thanks for your help guys!

In my eager to find more information I got stuck in the peter pan reroute thread... long read…awesome...

I'm sure of that the t-stat is working. I have no problems with the fan switch. I'll check in- and outlet to the heater core just to make sure they are as before the reroute. Next step is cardboard in front of the rad.

Thanks!

Andreas

I know. However, I can run all day long in 100* summer heat, under the SM lap record. I wouldn't have it set-up like that if it didn't matter. I'm going to throw a restriction in there and see if it helps a bit. I've even thought about sticking a ball-valve in there.

I would consider moving that return line to the bottom of the radiator. I don't think it would affect your warmer weather cooling.

I was trying to figure out why the car I was tuning last week took so god damn long to get up to temp, then i remembered he installed the begi reroute and put the return on the upper radiator hose. I'm having him splice it back into the lower.

That just makes no sense at all. The whole point of the re-route is to cool the hot water coming from the heater core. If you route it to the lower hose you are basacly doing the samething Mazda did in the fist place

The whole point of the reroute is to pull the coolant flow to top of radiator from the back of the head instead of the front, providing equal cooling across the cylinder head.

The heater core routing is peripheral...but can contribute to warmup and overall temp.

I designed mine like this for a reason. Returning hot water through the motor means its going to overheat on the track. There is a reason that proper racecars don't recirculate water like a streetcar.

If I only drove this car on the street, I'd have a stock cooling system.

wrong; that's not the point.

not really but ok.

Just to help me sort things out (I don't have my car at home). Is it the upper or lower heater hose that goes to the rear housing in the oe set up?

:facepalm::facepalm:

http://www.boostedmiata.com/gallery2...serialNumber=1

thx scot

I thought the heater core return was hot water and then it mixes with the cold water in the lower rad hose? And the re-route brings the hot water to the top of the rad hose so itgets cooled through the rad? I'm I wrong? Or is he talking about the rear termostat re-route?

I have a m-tuned rear temostat re-route.

yes, this is how street cars work.

Never mind then

Thanks Brain!

As far as I can see, the hose goes from the rear house to the upper heater inlet to help flow thru the heater core. I'l test to swap these.

thanks!

The only reason I brought up the heater core was because there were a number of folks doing this in the past, and it was part of the BEGi turbo kits. If you didn't touch the heater core return, don't now.

I have done 3 tests on track

1st. Begi race reroute with heater core return in stock location-Overheated in maybe 1/2 a lap
2nd. Same as first, only ducted, completely. Overheated after about 3 laps.
3rd. Ducted, return AFTER t-stat. Am yet to overheat.

To the OP, throw some cardboard in front of the radiator if you cant get the temps up.

noes!!! Someone finally substantiated what I created a year ago. The old ferrari "dual thermostat" thing would be nice on the miata. someone should come up with a high-volume thermostat.

I have done 2 tests on the track.

both on a 1/2 mile straight.

1. 2" radiator no undertray - Overheated anything over 100mph.
2. 2" radiator w/cooling panel and undertray - normal temps peaking at 130mph.

stock cooling system.

Are we really going to argue this shit? Was it 100* ambient? Were you under the SM lap record?

Its much easier to get air through a radiator at speed on big straights than a bunch on low speed twisty crap. I could make my stock 1.6 overhat on a local 1.3 mile 16-turn course, not on the 1.7 11-turn course.

It was 98*F ambient IIRC nice warm August day on the second attempt; about 4 seconds slower than SM record IIRC. Just sayin' homey. If we are talking street cars, no reason to move the heater core return. I'm curious to the flow differential between the upper hose once the thermostat opens and the heater core return...

words to live by.

I have the same issue as the OP, I have the 2" Mushimoto rad and the M-tuned reroute. The thermostat and fans all operate correctly and the car will come up to 94C when stuck in traffic, but if you get moving with much speed the coolant temps drop to around 80C.

I'm sure the issue is that the radiator just works too well, so the amount of coolant that goes through the closed thermostat is enough flow to keep the engine below operating temp.

I'm just going to block off part of the rad for the winter and call it a day. I picked up some corrugated plastic that I'm fairly sure is made of polypropylene so it should be ok with the temps, and won't fall off the first time it gets wet.

I guess that will be solution for me as well. After all I hardly use the car in winter. I think I'll pay some more attention on my high IAT when in boost instead.

Thanks!