2001 Montana thermostat problems

[jlstmary7]

My husband and I purchased a 2001 Montana in early May 2005. WE have just started having some problems. At first the Service Engine Soon light came on so we went to Auto Zone, had them run diagnostics and they said we needed to change the temp. sensor. So he did and it didn't fix the problem. A couple days after it was replaced the light came back on and we went through the whole thing again. So he has replaced it for the second time. Now however, he changed the oil 2 weekends ago and noticed a carmely substance on the oil cap. When drained the oil looks the way it is supposed to, it is just carmely on the top of the head. Please offer any suggestions to fix this problem. Some of his buddies think it is the thermostat, some other guys think it is a blown head gasket. I would really appreciate any clues to help us solve this mystery!! Thanks so much!!

Have a great day!

[GTP Dad]

Welcome to AF! Does the temperature guage go into the red when you are driving? If it doesn't the cause of your problem is not the thermostat, as it is working properly. I would be very curious to know the exact code they gave you at Autozone. If you replaced the temp sensor twice I doubt that is the issue either. The caramel looking substance indicates moisture in the crankcase but that may be a part of normal driving as some moisture naturally accumulates in the engine if you use it for short drives.

If you have the code please post it and we will see what we can do to help.

[cdru]

Originally Posted by GTP Dad

The caramel looking substance indicates moisture in the crankcase but that may be a part of normal driving as some moisture naturally accumulates in the engine if you use it for short drives.

As many others here can attest, it can also be a sign of your intake manifold gasket leaking coolant in your oil. However with the colder temperatures starting to come about, it may just be plain moisture*. The only way to tell for sure if it is coolant or just moisture is to have it analyized by a lab. Blackstone Labs can do exactly this for about $20.

Do you notice any change in coolant levels?

As GTP Dad said, posting the code would shed some more light. A blown head gasket would usually have other signs.

*-I just fixed a coolant leak this weekend. I was POSITIVE it was going to be yet another intake gasket leak (I've had 2 in the past year) because I saw some of the gunk in my oil cap as well as several key areas along the intake manifold. It looks like it was just a coolant hose that had a small hole in it that was leaking coolant onto the head/intake/block, and the gunk in the oil cap was just moisture (not coolant). A longer drive allowing the engine to get up to operating temp for a while should drive off most of the moisture that may accumulate.

[intrex_ed]

I'm having the same problems with another 2001 Montana. I've replaced the temp. sensor a couple weeks back and the engine light went off. After a week or so it came back on. The reading they had on the OBDII, was that the tempature sensor is reading below normal. JLSTMARY7 I would check to see where your gauge is at. My would stick around 1/4 but when the check engine light came on it wouldn't even come up.

Please post any progress as I will do the same.

Thanks,
Tony

[intrex_ed]

HERE'S THE CODE:



P0128
Coolant Thermostat
(Coolant Temperature Below Thermostat Regulating Temperature)

[jlstmary7]

Okay well here is the latest. I went to Auto Zone today and got the code. It is PO128. The same one that was recently posted. The guy at Auto Zone told me the same 2 things...Thermostat and Head gasket. My husbands buddy at work says it is probably the thermo. since they checked the radiator and the coolant level hasn't changed. When I run the van the thermo. stays right at 160, the lowest level. I had it running for probably an hour today and it never got above that number. I hope this can shed some light and you all can help! Thanks for all the help so far!

[cdru]

I'd replace the thermostat. Others here on the forums have done that to correct the error code.

[jlstmary7]

Will do! Thanks for your help. I will let you know the outcome!

[intrex_ed]

thermo. has been replaced on mine, but the code was thrown a week afterwards. i had autozone erase the codes and hopefully it will be gone now. will know in a week or so...

[GTP Dad]

To explain the code the engine computer is set to run at a specific temperature range. If the engine does not heat up to that particular range the engine computer will detect it and give you a code. Usually it is caused by a thermostat that is stuck in the open position. Changing the thermostat should correct the code and the entire issue.

[jlstmary7]

Can you tell me how easy/hard the thermostat is to replace. I think my husband is going to do it this weekend, and just wants to know what he might be getting into!! Thanks so much for taking the time to help us with this problem!!

[GTP Dad]

The thermostat is not hard to change the key is making sure you have drained enough coolant out of the radiator. Once it is drained down, remove the upper radiator hose, then unbolt the thermostat housing. Remove the housing and thermostat, scrape the gasket surface clean. Then replace the thermostat and gasket, replace the housing and tighten, don't overtighten, refill the radiator. This is the hardest part, make sure you get all the air out of the system as the air will cause the engine to overheat. If you have a radiator cap leave it off until the thermostat opens and the coolant level will drop, refill until full and replace the radiator cap. Then refill the reservoir to the proper level and the job is done.

[cdru]

Originally Posted by GTP Dad

The thermostat is not hard to change the key is making sure you have drained enough coolant out of the radiator. Once it is drained down, remove the upper radiator hose, then unbolt the thermostat housing.

On paper, that sounds easy. In reality though, it's quite a bit harder. Due to a brilliant design decision, it's basically impossible to get to the bolts that hold the housing to the intake manifold. The throttle body gets in the way from above, and the exhaust crossover pipe gets in the way from the side. You will have to remove one or the other to get to the bolts.

To remove the TB, you will need to remove the two bolts holding it on. The rear bolt will be blocked by the bracket for the bypass pipe, so that too will need to be detached from the block. So you will want to drain the coolant otherwise you will have a mess.

Alternatively, you can remove the upper intake with the TB attached. It's not that much work, approximately 1/2 hour to get it off if you know what to remove. And you don't have to worry about disconnecting the TB or removing the bypass pipe.

Removing tje cross over pipe may be less messy route, but the bolts likely will be rust welded so expect to snap them off and replace them. Getting to some of the bolts though is a chore.

scrape the gasket surface clean.

The gasket is rubber and should come out with the thermostat. There is no other gasket material present (unless someone added it improperly).

[jlstmary7]

Originally Posted by intrex_ed

thermo. has been replaced on mine, but the code was thrown a week afterwards. i had autozone erase the codes and hopefully it will be gone now. will know in a week or so...

Intrex_ed,

Did you replace the thermo. yourself? My husband and his dad tried to replace this weekend and couldn't get it out. They worked on it for about 3+ hours. I am pretty sure they got one bolt off, just couldn't get the other...Any suggestions??

[cdru]

The rear bolt doesn't have to come out, only losen. The housing's rear bolt hole is really slotted. The hard part is getting the housing around the thermostat as the bulk of the thermostat fits into the housing.