weird engine temperatures

tording · Jan 1, 2007

Ok guys. I kinda have a weird question. I want to know that for those of you with 180* thermostats what does your temperature guage do? Mine does all kinds of different things. Sometimes I can drive my car and the temp guage will hang down in the 150-170 range the entire time. Sometimes the guage will come up to what seems to be about the 200* mark and then drop back down to the 150* temp range and stay right there. Sometimes it will come up to the 200* mark and hang right there and stay there. And sometimes it will come up to the 200* mark and very very very slowly climb a little higher like up into the 205-210 range or so. The car has never overheated on me yet but it does such weird things with the temperature guage and I don't understand why. I have an 180* thermostat so it should come up to 180* and hang right around in that range right? Why doensn't mine do that?

vristang · Jan 1, 2007

tording said:
Ok guys. I kinda have a weird question. I want to know that for those of you with 180* thermostats what does your temperature guage do? Mine does all kinds of different things. Sometimes I can drive my car and the temp guage will hang down in the 150-170 range the entire time. Sometimes the guage will come up to what seems to be about the 200* mark and then drop back down to the 150* temp range and stay right there. Sometimes it will come up to the 200* mark and hang right there and stay there. And sometimes it will come up to the 200* mark and very very very slowly climb a little higher like up into the 205-210 range or so. The car has never overheated on me yet but it does such weird things with the temperature guage and I don't understand why. I have an 180* thermostat so it should come up to 180* and hang right around in that range right? Why doensn't mine do that?

Normally, the temp would hang around 10-15F over the stat rating. So, you sould be seeing 190-200F temps.

However, the stock temp sending unit and gauge are accepted as being far from accurate.

Swap the stock gauge for an aftermarket before getting too concerned!

Or, just make sure that there is no corrosion in the sending unit system.
Pull the plug from the sensor, and remove any corrosion.

just a thought,
I hope to hear what others think,
jason

tording · Jan 1, 2007

vristang said:
Normally, the temp would hang around 10-15F over the stat rating. So, you sould be seeing 190-200F temps.

However, the stock temp sending unit and gauge are accepted as being far from accurate.

Swap the stock gauge for an aftermarket before getting too concerned!

Or, just make sure that there is no corrosion in the sending unit system.
Pull the plug from the sensor, and remove any corrosion.

just a thought,
I hope to hear what others think,
jason

Its funny you mention the aftermarket guages because I am looking at them online right now. I got some gift certificates for summit and I think I am gonna pick up some nice Autometer coolant temp and oil pressure guages just to be sure its not my stock guage. As far as water temp do you guys think the 120-240 or the 140-280 temp range is better for a street car? I can't really decide one way or another.

HISSIN50 · Jan 1, 2007

I'd probably go for the latter (140-280*F) range gauge. We dont care about losing 20*F at the bottom of the range but it's nice to have a little more on top - only for balance (so the needle is in the middle of the gauge, and not near pegging one end. ). That's just me. My personal thing is mech temp gauges and electric OP gauges when they're going in pillars (I'm too lazy to run copper or braided line to a pillar).

For the wandering temps, has the system been down on coolant lately? Air in the system will cause a gauge reading to wander. It can also damage an unbalanced T-stat. Also, by chance does it run coolest when at speed, and then heat up while idling or moving slow?

As Jason said, and you thought, get that real gauge on there and diagnose from there.

Good luck.

tording · Jan 1, 2007

HISSIN50 said:
I'd probably go for the latter (140-280*F) range gauge. We dont care about losing 20*F at the bottom of the range but it's nice to have a little more on top - only for balance (so the needle is in the middle of the gauge, and not near pegging one end. ). That's just me. My personal thing is mech temp gauges and electric OP gauges when they're going in pillars (I'm too lazy to run copper or braided line to a pillar).

For the wandering temps, has the system been down on coolant lately? Air in the system will cause a gauge reading to wander. It can also damage an unbalanced T-stat. Also, by chance does it run coolest when at speed, and then heat up while idling or moving slow?

As Jason said, and you thought, get that real gauge on there and diagnose from there.

Good luck.

I like your thought on the temp guage. I think your right and I will probably go with the 140-280 range guage. I am going to put them in a guage cage in the middle vent of the car. I had a set of the liquid filled pro comps in my other mustang I had in the middle vent and I loved it. They are very nice guages. I also like the ultra lites that are not liquid filled and they are a tad cheaper so I might go with them.

I did just put in a new 180* thermostat so I lost some coolant then and right after I did the thermostat I didn't get a hose clamp tight enough and I lost some coolant, enough that my low coolant light came on. If it is air in the system how do you get rid of it? I have had mustangs prior to this one and I never had to do anything special. Just filled the resovior and radiator up with 50/50 mix and called it a day. You are correct also that it does seem to run the coolest when I am moving and when I am idling or going slow through traffic is when it runs the hottest. Does this confirm the air theory or does it mean something else? thanks for the help on this guys.

Idwitheld-1` · Jan 1, 2007

You may have a blown head gasket. When I say blown, I mean a micro leak.
Run your heater vent. Does your heat change up and down. Do you loose heat completely?
Compression stroke forces hydrocarbons into coolant. Coolant looses efficiency to cool (car runs hotter). Coolant outgasses in radiator and the cycle is repeated.

Pull your plugs. Any of them yellow or "steam cleaned"? Excess steam from your tail pipes? Glycol smell from tail pipes? Pull the headers. Any Tubes blown clean?

Get a block tester look for hydrocarbons in your coolant.

tording · Jan 1, 2007

Idwitheld-1` said:
You may have a blown head gasket. When I say blown, I mean a micro leak.
Run your heater vent. Does your heat change up and down. Do you loose heat completely?
Compression stroke forces hydrocarbons into coolant. Coolant looses efficiency to cool (car runs hotter). Coolant outgasses in radiator and the cycle is repeated.

Pull your plugs. Any of them yellow or "steam cleaned"? Excess steam from your tail pipes? Glycol smell from tail pipes? Pull the headers. Any Tubes blown clean?

Get a block tester look for hydrocarbons in your coolant.

Hmm. thats not good. I haven't noticed the heat going up and down or losing heat completely. I do however seem to have a lot of "steam" coming from the tailpipes a lot. I haven't noticed a glycol smell but it might be there. I will pull the plugs and take a look.

I have also noticed that in the past week or so it overall temp of the car seems to heat up a lot faster that it use to.

What is a block tester and how do I look for hyrdocarbons in my coolant?

Just so you guys know the engine does have 170k miles on it.

HISSIN50 · Jan 1, 2007

tording said:
I did just put in a new 180* thermostat so I lost some coolant then and right after I did the thermostat I didn't get a hose clamp tight enough and I lost some coolant, enough that my low coolant light came on. If it is air in the system how do you get rid of it? I have had mustangs prior to this one and I never had to do anything special. Just filled the resovior and radiator up with 50/50 mix and called it a day. You are correct also that it does seem to run the coolest when I am moving and when I am idling or going slow through traffic is when it runs the hottest. Does this confirm the air theory or does it mean something else? thanks for the help on this guys.

In theory, the systems self-bleed. However, sometimes they need help. I'll start with a cold engine. Get the drivers-side front a little higher than the rest (if feasible) and remove the radiator cap. I let it idle like this till the stat opens and then a little longer. Just be real careful of hot coolant splashing out of the radiator neck. I would stuff a rag or something over the radiator neck. Air should be purging during this time.

The fact that the car runs cooler at speed simply indicates that the fan might not be moving as much air across the coil as it could be. I wouldn't really sweat it for right now, unless temps simply creep up indefinitely when the car is slowing or stopped.

You can loan-out a cooling system pressure tester from the parts store - that can help to tell you if there is something really wrong with the system (the stuff that ID is getting into). It's also sometimes nice to know what kind of pressure you're holding (each PSI in the system raises the effective boiling point ~3*F. 16 PSI = ~50* higher boiling point than if at atmospheric pressure).

Personally, I wouldnt be thinking that there's really anything wrong right now. Some real gauges (for a gauge cage, I think I'd do a mech OP and coolant temp gauge, BTW) and watching what the system does for a few days might reveal more.

Random thoughts. Good luck.

tording · Jan 1, 2007

Ok. I will work on this in the morning as well as pulling the plugs. If the head gasket does have a small micro leak is there any danger of driving the car like this for a short while till I know for sure so I can fix it? It is not that far of a drive to work. Like 4 miles. I just don't want to damage anything else. I just will keep my foot out of the gas till I know.

Idwitheld-1` · Jan 1, 2007

I agree with Hissin50. Cooling fan clutch may be the culprit. They are about 32 bucks and easily testible. The viscoelastic goo leaks from the front seals and doesn't allow the fan to operate properly. The gauge thing is possible. Your symptoms are exactly what happens when you have air in the system near the temp sensor.

If that fails, the block tester is available from NAPA. About 65 bucks. But, if you are not loosing heat then I doubt you have a outgassing problem. Does your thermostat have a hole in it?

I think it would be ok to drive. Just don't hammer on it.

tording · Jan 1, 2007

Idwitheld-1` said:
Does your thermostat have a hole in it?

The 180 thermostat that I just put in the car a couple weeks ago does have a small hole at the top of the thermostat looks like for a vent. However, the 160 that the guy that previously owned the car had in did NOT have this hole. Did this cause damage to something maybe??

Also I feel I should tell you that I took out the small sending unit for the temp guage. When I took out the sending unit from the lower intake No coolant at all came out almost like there is none in the intake. Is this because of air trapped in the system maybe??

Idwitheld-1` · Jan 1, 2007

tording said:
The 180 thermostat that I just put in the car a couple weeks ago does have a small hole at the top of the thermostat looks like for a vent. However, the 160 that the guy that previously owned the car had in did NOT have this hole. Did this cause damage to something maybe??

Also I feel I should tell you that I took out the small sending unit for the temp guage. When I took out the sending unit from the lower intake No coolant at all came out almost like there is none in the intake. Is this because of air trapped in the system maybe??

Make sure the hole is mounted at the highest point straight up. Just a vent hole to release any trapped gas.

If the engine is running then fluid should shoot out the ECT port. Hot or cold you should have fluid coming out that hole. Are you sure your belt is not slipping and is the propper length? I will also assume you have the proper fluid level in the car.

If while the car was running and you removed the ECT the air should have been pushed out by the fluid. The fluid should squirt out.

Also, for comparison purposes if you run the car without the thermostat does your temperature still fluctuate wildly? This would rule out the thermostat.

tording · Jan 1, 2007

I removed the temperature sender while the car was not running. There was still no fluid that came out of the hole however. I thought coolant would come out but it never did. I am pretty sure that the pulley is not slipping and yes I am pretty sure the belt is the right length. I also do have the proper fluid lvl in the car. I am really leaning towards there being an air bubble trapped in my intake because of the no fluid coming out of the ECT port when I removed the sender. A friend and I are going to check it first thing in the morning.

HISSIN50 · Jan 2, 2007

FWIW, the ECT and gauge sending unit are two separate units. Last time I removed the gauge sending unit, a little bit of coolant did dribble out.

If you do the burping procedure, it should help rule out any air pockets (contraction of fluid notwithstanding).

Good luck.

tording · Jan 2, 2007

Yeah, I took out the guage sending unit not the actual ECT. When I took it out I could look down in the intake and couldn't even see any coolant that I remember. I would have thought I would have been able to at least see some. This was with the motor cold though. In the morning I am going to do the burp procedure that you said. Just going to jack up the front driver side of the car and start the car with the radiator cap off. Let it warm up till thermostat opens and see what happens. I will keep you posted.

tording · Jan 3, 2007

Ok so I have come to the conclusion that it is not a head gasket so that is good. I think one of the main causes was the fan. I happend to have another fan from my GT I use to have so I put it on. The clutch on the new fan is much stiffer and the old fan clutch did seem to be leaking some fluid from it.

tording · Jan 3, 2007

I also have another question. Is the middle mark in my temp guage 200 degrees like I have marked? The only markings are 130 and 270. Is this correct?

tording · Jan 3, 2007

I have another question. On my temp guage is the middle mark 200 degrees like I have marked in my drawing? The only markings are 130 and 270 so if my calculations are correct it should be 200 where I have it marked. Is this correct?

HISSIN50 · Jan 3, 2007

Glad to hear the fan stuff helped. As wise-old ID noted, when the fluid starts to leak out, the bite in the viscous coupling is affected. If the bitmetallic spring in there takes a dump, it can also hinder performance (the spring is what moves, allowing fluid to pass through an orifice).

I tried to interpolate the stock gauge and it wasnt worth it. Once I had a real gauge on there, I found that my stocker had read about 35*F too cool at 165*F! Please don't rely on that POS too much.

Good luck.

Idwitheld-1` · Jan 3, 2007

Aw shucks Hissin, now I'm blushing.

I still would be concerned with the air pocket in the lower intake. If you have the sender out, fill the intake with fluid then check it in a day or two. I wonder if the air pocket comes back?

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