Temp guage reads cold and radiator fans running!

Last night my wife called me while driving and said the heaters wern't working, the temp guage was reading cold and the service engine light was on. I had her call onstar and the diagnostics said it would be OK and to get it into a shop in the next 7 days.

I drove out and met her on the road just in case and sure enough, the Temp guage was totally cold and no heat, BUT the radiatior fans were running wide open. This morning when we started the van the radiator fans kicked on again in less then a minute and stay on.

I've read in another thread where this has happened to a couple other people. In each case they replaced or repaired the temp sender and reset the codes with a code reader. They also said the problem has contined to occur and they just reset the computer with a code reader and it's fine again for a while.

So, where do I get one of these code readers so that I can reset mine. Or, what do I need to do to fix this?

Thanks!
DC

Hi DC,

You didn't mention what year & engine you have, but it could be a number of problems. I suspect that you may have a thermostat that is stuck (or sticking) OPEN. Besides that, make sure your radiator is full, along with the coolant reserve tank.

As for the code reader, you can normally get one at almost any decent auto parts store. You can also "borrow" one from some parts stores too. Try to borrow one and read the code (it may be a stored or "history" code if the SES light is not on) and post it back here.

I have a similar issue you can read about at the link below.

http://www.automotiveforums.com/vbulletin/showthread.php?t=659006

The summary is that the coolant doesn't reach the expected "normal" temperature, so I got a P0128 code. I believe it caused by my thermostat being stuck open, and I have not been able to replace it yet. Check it out and see if you have the same symptoms.

Let us know what you find.

Take Care,

Thanks Greg!

Sorry about my lack of information!
It is a 2001 Venture with 110,000 Miles on it
The coolent level is fine and I flushed and replaced the coolent last year.

I did see your thread. I think you hit the nail on the head with the Thermostat. The Van has been running on the cool side for about a year or so and it was a cool night the evening that this started. It is interesting to think that the computer is running the radiator fans now on a kind of "fail safe" because the coolent didn't get hot enough! Better safe then sorry.

So, it sounds like I need to buy a code reader so that I can reset the computer so that the fans will shut off and replace the Themostat so I don't have this problem again. I'll probably replace the plugs at the same time (that sounds like a fun project too (with OEM plugs of course)).

Anything else you can think of?
Thanks again,
DC

try replacing your coolant temp sensor, if they fail to send a signal the computer ,will trigger a fail safe ( fans running all the time) to prevent the motor from overheating. will also cause the CEL to illuminate.

Thanks,
I'll add that to my list of things to do to the Venture this weekend.
So far I've got
1. Thermostat
2. Plugs (OEM)
3. Coolent temp sensor

Anything else while I'm working on the back side of the engine?

BTW, I flushed and replaced the coolent last year, I understand old Dexcool can cause some nasty trouble.

Thanks for all of the tips!
DC

DC,

I don't think your temp sensor is bad because it is probably showing what the actual temperature is (you said "no heat" was a symptom). But if it is not too much money or too much problem to replace, you could replace it.

I got the readings from the computer system (I have a data-logger) and compared them to the temperature measured using an infrared thermometer, and they were pretty close.

Take Care,

Thanks Greg,
I think you are right. The van has been running about at 1/4 on the temp guage on the dash and has probably been pretty close to that magic 170 number for some time.

My guess is the Themostat is opening too much and my wifes drive the other night finally tripped the computer.

I haven't looked to see where everything is in the engine compartment yet. I had thought about replacing the sensor at the same time only because it sounds like it may be easier to do if its located with the thermostat. From what I've read this sounds like it will be a fun little project!

I also saw that your thermostat was a 195 unit. Is that factory? Should it be the one I should get?

I'll get the parts tomorrow including a Code reader. I found a nice one at Schucks that they are holding for me and will go on clearance tomorrow. It's a Code Scout and it actually says what the code is as well as the code. I hope it will do the job.

I also have a infra red thermometer, I'll double check my readings with it. Thanks for the tip.
Dick

I believe 195 is the factory temp. It's a quick and easy change with relatively easy access. The thermostat however is another story. Some people have had luck with losening the bolts just enough to get the housing off. Others have said it required removing the exhaust cross over pipe. If you have to go the later route, plan on getting 6 new studs and nuts because they will break off.

This is either the temp sensor or thermostat. Since you don't have heat inside the van, the cause is most likely the thermostat, its sticking open. The fans running all the time is a result of the computer sensing that the engine should be warming up, given the amount of time the engine is running. Since its not warming up, for whatever reason (bad temp sensor maybe) the computer triggers the fans to run all the time to avoid damaging the engine if in fact it was the bad sesnor and the fans didn't come on youd overheat. This can also be triggered if the thermostat is stuck open, computer doesn't know that, all it knows is the the temp sensor is still showning a cold engine. But you know becasue its still cold inside the van.

You can get the thermostat housing off without pulling the crossover pipe, but its time consuming. I usually leave the crossover pipe if it looks rusty and bad, as I don't want to be fixing broken studs later.

Thanks guys!
I started on it this morning. I did buy a 195 degree thermostat so I'm headed in the right direction so far.

I thought I'd jump back on the computer to see if this can be done without removing the cross over pipe and you've answered my question already! If its been done before, I can do it! I think I'll head out to the auto supply and get a new set of offset wrenches for that lower bolt. I couldn't get the lower bolt with a standard 13mm wrench reaching from the back, just no leverage.

BTW, I did get a code reader and reset the computer and the van runs just fine again, although it still runs a little cold. About 1/8th to 1/4 on the temp guage. It's got to be the thermostat. It's nice to have heat again though!

To everyone who has responded here, thanks! Its nice not to feel alone!

Well that was fun. And yes, it can be done without removing the crossover pipe, but not by much! I sure am glad that the GM engineers made a slot for the lower bolt in the thermostat housing. I'm not sure I would have been able to thread the bolt back in with my fingers if I would have had to remove it all of the way.

After installing the new thermostat, refilling the coolent and bleeding the lines it's working great!

Thanks again for all the help.

Hey, are there some vans more vulnerable to the infamous intake gasket? I've got a 2001, should I expect trouble soon?

Thanks,
Dick

I wouldn't say one is worse than the other, they all had poor gaskets up to around 2003/2004. If the gaskets are original and your past 100,000, I would personally replace them with the updated version, along with the intake bolts, the new o-ring distributor shaft seal. Just wait until it warms up outside and go for it.

Either way, open the hood up every once and awhile and take a close look at the gasket on the sides of the engine and look for sweating/leaking. Look under the oil cap, and watch your oil and coolant. If all looks good, your fine, just be observent and watch it closely.

Well that was fun. And yes, it can be done without removing the crossover pipe, but not by much! I sure am glad that the GM engineers made a slot for the lower bolt in the thermostat housing. I'm not sure I would have been able to thread the bolt back in with my fingers if I would have had to remove it all of the way.

After installing the new thermostat, refilling the coolent and bleeding the lines it's working great!

Thanks again for all the help.

Hey, are there some vans more vulnerable to the infamous intake gasket? I've got a 2001, should I expect trouble soon?

Thanks,
Dick
So just HOW did you get to the bolts to get the housing off?

And - what is your temperature reading on your gauge now?

Take Care,

I wouldn't say one is worse than the other, they all had poor gaskets up to around 2003/2004. If the gaskets are original and your past 100,000, I would personally replace them with the updated version, along with the intake bolts, the new o-ring distributor shaft seal. Just wait until it warms up outside and go for it.

Either way, open the hood up every once and awhile and take a close look at the gasket on the sides of the engine and look for sweating/leaking. Look under the oil cap, and watch your oil and coolant. If all looks good, your fine, just be observent and watch it closely.

Thanks, That is great advise! I had heard that they updated the gasket, I was hoping that mine was one of those updated!!! So far I haven't seen any weeping at the gasket and the oil cap shows no sign of milky discoloration nor does the oil when I change it. I will continue to keep a close eye on things. We love the van and would like to keep it until something better for our family comes along. It seems like many can't wait to get rid of their ventures, we're not one of those people.

Thanks again!
Dick

So just HOW did you get to the bolts to get the housing off?

And - what is your temperature reading on your gauge now?

Take Care,

Hi Greg,
I removed water over flow and support bar that it clamps onto. Then I pulled the airbox cover and O2 sensor. Then I disconnected the intake hose to the throttle body and moved it up out of the way. I did the same with the cooling line that comes out of the top of the water pump (the metal one). I would have liked to get rid of it all together but didn't know how to unhook it at the other end? Still, after unhooking the little hoses under the throttle body and the other one at the waterpump side I was able to move it out of the way.

The top (front) bolt on the manifold was a piece of cake, just a standard socket and extension. The lower (back) was a long tedious 1/8th turn at a time with a 13 mm wrench. I had to buy a longer one at the beginning because I couldn't get enough leverage to get it loose with the one I had. You have to reach in behind it to loosen it (wrench pointing towards the firewall). After I loosened it with the long wrench I used the shorter one to back it out. Just don't back it out all the way because it would be a real bugger to try and get threaded back in! Fortunatly the back hole on the housing is slotted so you can get it off without taking the bolt out all the way. You will have to back it out almost all the way though!!! Good luck!

Once you get it free you'll have to jocky the housing around a little to get it out. Its a tight fit with the exhaust cross over pipe. Putting it back on with the new thermostat is just as fun!

The temp of the van is great now. right around 1/3 or more. Heaters work great too!

Thanks again for all your advise. If anything changes for the worse I'll report back, but so far so good!!!

Dick