Overheating when A/C is on?

[PaRaDoX]

So here's the background and potentially relevant mods on the car.
Stock Motor
P1SC Intercooled Procharger
Meth/Water injection
Longtube headers
Mishimoto triple core radiator installed in December
Mishimoto Electric Fan installed in december
MSD 2-Step Launch Controller installed in December
New Water Pump Installed in December

Took car to the a shop because it was overheating when the A/C was turned on. If you turn the A/C off and put it to blow Hot air into the cabin the car will return to operating temps within a minute or two.
Shop Replaced Thermostat and Thermostat housing
Shop has flushed the cooling system and promises no air in the system.
Shop has replaced the CHT (Cylinder Head Temp sensor)
Shop has changed oil/filter (claimed oil was low)
Shop has re-charged A/C
Shop has verified the Fan is kicking on.
Shop claims that when the car is reading that it is overheating it is reading 280 degrees on their Handheld device but with a temp gun its reading between 190-202 on different areas of the system.

This issue happened around March when the weather here in Texas started to get warmer.

Techs are stumped. Any ideas?

 

[cavero]

They pressure-test the cooling system? If it's not holding pressure the coolant will boil at a lower temp

 

[BruceH]

Maybe put the stock radiator and fan back in?

 

[thump_rrr]

Anyone try replacing the thermostat?
The heater hoses come straight from the engine block so if you can cool the engine with the heater core your problem might be with the stat/ radiator/fan.

If you have an excalibrator programmer you can set it up to check cylinder head temp and also the first and second stage of the fans being commanded on.
You will be able to see at what temps the fans are being commanded on and if they actually come on at those temps.
Does the mishimoto have a dual stage cooling fan like the original?

The original fan comes on at I believe 205F on low speed.
If the A/C is turned on the fan automatically comes on in high speed and stays there.

Don't believe the shop and test the car for yourself.

Get the car to normal temperature and let it is with the Ac off.
Monitor cylinder head temp and see if the fan kicks on at low speed.
If it does go to test 2 and start the A/C.
Does the fan come on high right away?
If not there is a problem there.

 

[PaRaDoX]

They pressure-test the cooling system? If it's not holding pressure the coolant will boil at a lower temp

Im not sure however when the car claims its completely overheating there is no bubbling or any coolant spillage.

Maybe put the stock radiator and fan back in?

I would however the stock radiator was replaced because the plastic housing cracked.

Anyone try replacing the thermostat?
The heater hoses come straight from the engine block so if you can cool the engine with the heater core your problem might be with the stat/ radiator/fan.

If you have an excalibrator programmer you can set it up to check cylinder head temp and also the first and second stage of the fans being commanded on.
You will be able to see at what temps the fans are being commanded on and if they actually come on at those temps.
Does the mishimoto have a dual stage cooling fan like the original?

The original fan comes on at I believe 205F on low speed.
If the A/C is turned on the fan automatically comes on in high speed and stays there.

Don't believe the shop and test the car for yourself.

Get the car to normal temperature and let it is with the Ac off.
Monitor cylinder head temp and see if the fan kicks on at low speed.
If it does go to test 2 and start the A/C.
Does the fan come on high right away?
If not there is a problem there.

I'll check that out. I have an xcal3. The thermostat/housing is not an issue. I forgot to list that im sorry. (added in original post) However new symptom, drove the car and it overheated at stop and go traffic, got on the highway and turned heat all the way on (roasted myself) and it went back to operating temps.

 

[JeremyH]

Do you have a fan shroud?

 

[07 Boss]

Have you thought about an electric water pump? When your in stop and go traffic you are not only getting minimal airflow but minimal coolant flow. With an electric pump it is running at the same speed all the time and flowing a good amount of coolant. My car actually cools down when idling and I have the fan switched on.

 

[BruceH]

I think the easy fix would be to install a stock radiator and fan or 2013 GT500 fan.

 

[PaRaDoX]

There is no fan shroud. I will take a picture of the set up once im home. Id really rather not throw anymore money into this issue since everything was working fine with the stock setup. The stock just busted so I thought upgrades were in order. Apparently I was wrong.

 

[thump_rrr]

Ok since this shop is just a bunch of parts changers this is what you will need.

Xcal-3 which you said you have.
A laptop with a USB port loaded with SCT LiveLink 6.5 which you can download from their site.
A usb printer cable to connect the XCal-3 to the laptop.

I won't go step by step but you need to datalog 4 pid's only.
CHT (Cylinder Head Temp.)
ECT (Engine Coolant Temp.)
Low speed fan
High speed fan.

The CHT and ECT can be found in environmental
The fans can be found under fans.

The important thing is that this test should be performed when the car is at ambient temperature like in the morning after being parked all night long.

The first goal is to check if the CHT sensor is accurate so by turning the key to position #2 and not starting the vehicle we will be able to see what temp the CHT is showing and if it is accurate.
The XCal will tell you to start the vehicle but don't.
Once you start data logging the CHT and ect should be the same as the outdoor temperature or close.
If for example it is 90F outside and the CHT shows 140F before you start the car you know that the CHT sensor or wiring is screwed.

If the CHT is ok go ahead and start the car.
You may need to start the data logging session again.

Now allow the car to warm up on its own at idle.
While it is warming up turn the AC on and check to see if the cooling fan turns on.

Now turn the AC back off and watch your CHT and ECT steadily rise.
As the temperatures rise you should see the cylinder head temp rise a little quicker than the engine coolant temp.
When my coolant temp reaches 205F my CHT is around 230F for reference purposes.

The engine coolant temp does not have a sensor.
The temperature is derived by taking the cylinder head temp and I believe the Intake Air Temp.
The low and high fan should both be showing 0.00

On my car low fan is set to turn on when the Engine coolant temp is at 205F and off at 195F.
My high fan is set to come on at 218F and off (back to low) at 213F

Your temperatures may vary depending on who did your tune.
The important thing to check is that when your low fan value goes to 1.0 the fan starts and runs on low. When the high fan value goes to 1.00 the fan goes to high.

You definitely need a fan which has a shroud because a fan cannot develop static pressure without the shroud acting as a Venturi.
The other thing to check is that the fan is mounted behind the radiator towards the motor and that it is a puller which means it is pulling the air towards the engine compartment.
I am running an AFCO radiator which is virtually identical to the Mishimoto with a factory fan and shroud with no issues.
Another thing to check is if the top and bottom radiator covers are in place because the car will cool poorly without them.
The top cover is the one when you open the hood that goes between the grill and the radiator and the bottom one goes between the bumper cover and the original radiator/swaybar support
Many people with aftermarket front bumpers or aftermarket rad supports forget or don't use this piece and it causes a lot of high speed overheating problems.

If you have any questions don't be shy to ask.

EDIT: if you replaced the thermostat with a lower temp unit the programming of the fans should also be changed to start sooner.

 

[CPRsm]

Jesus they did all that work before verifying what was wrong first?!
If they are testing the engine w a laser and it's only showing 200 degrees it's not overheating.
Open the cooling system and let it warm up. At 280 it would be boiling like a mother, or lock the engine.
Their scanner is reading what the ecu sees. Looks like you just have an electrical gremlin or bad part. A short/(worn/weathering wiring) in the ground can cause the gauge/ecu to read high. Sometime not at first, but climbs exponentially as coolant temps rise. Meaning coolant goes up one degree, sensor reads 2 deg higher. My man above me gave some solid tech on trouble shooting the sensors. I've replaced the battery in my laser temp guns a few times. We use the shit out of it. Most times it's verifying something like this

 

[one eyed willy]

I've tried many aftermarket fans, many shrouds and a few different combinations.

Nothing cools better than the stock fan. (Or even better the gt500 fan)

 

[silverpoison]

did you figure it out?

 

[PaRaDoX]

Looks like the fan isnt powerful enough. Haven't gotten it fixed yet unfortunately.

 

[s8v4o]

Got any pics of the fan setup? How many inches is your fan? How was it wired? Did they use the factory harness and and cut off the factory fan connector?

 

[skwerl]

There is no fan shroud. I will take a picture of the set up once im home. Id really rather not throw anymore money into this issue since everything was working fine with the stock setup. The stock just busted so I thought upgrades were in order. Apparently I was wrong.

This is your problem.

 

[s8v4o]

This is your problem.

I thought the same thing until I googled that type of fan. It's the typical slim fan with built in shroud that is apart of the mounting. I think the "no shroud" is a bit misleading. Perhaps I'm wrong.

 

[Eel Mit]

I thought the same thing until I googled that type of fan. It's the typical slim fan with built in shroud that is apart of the mounting. I think the "no shroud" is a bit misleading. Perhaps I'm wrong.

Thats not a shroud, its a blade / finger guard. A shroud acts like a funnel and covers the whole radiator core, forcing airflow even from the corners.

The pictured fan leaves a lot of area that will sit static and act like a heat sink, until the car moves.

The AC condenser acts like a heat gun, shedding hot air onto an already hot radiator.

 

[avinaj80]

On customer cars I have worked on that are f/i on which they decided to go with a "slim" fan setup, I have found (along with the major consensus) that these slim fans just don't pull enough CFM to keep these engines cool without a shroud. Had a customer of mine break down going up the Cajon Pass on the way to Vegas a couple years back due to his setup. Came back, threw his stock fan in, no problems since.

Yes, the biggest difference is definitely a shroud. The aftermarket fans may spin faster and have the potential to pull more CFM, but if it isn't shrouded? It's not going to perform properly. Looks to see if someone can fab you up a shroud. I would just go with the 2013 GT500 fan as the others recommended though. Hope you get it fixed soon though.

 

[Dino Dino Bambino]

There is no fan shroud.

That's almost certainly the problem as others have suggested.