2000 Chev Blazer 4 x 4
4.3 liter

In the morning when I first start my car up the temperature rises and it goes to past the half way mark on the gauge then the thermostat opens and it cools down to just before the half way mark on the gauge where it remains. Today when I was going to work I was stuck in a bit of traffic and the car was still warming up, well this time it went to past 3/4 and then it cooled right down to below the 1/2 way mark and I have had no other issues going to work.

I am worried about the fact it went to past 3/4 on the gauge, there has to be something wrong, the thermostat was replaced a couple of weeks ago, could it be faulty??

The only other things I could think of is perhaps my rad is plugged a bit? Is the fan not engaging?

Any ideas?

I have a feeling something bigger is going on.

Just a side note the system had air in it last week and I took it into the dealership to get fixed, the guy had mentioned how he sees lots of blazers with the gurgling sound behind the dash. They were able to fix it, they also pressure tested it and it was fine.

I have also put a new rad cap on the vehicle.

I am hoping someone has had a similar issue with there vehicle and might be able to offer me up a solution.

 

The ideas you mentioned are possible causes, but so is the chance that the engine coolant temperature sensor (ECT) is at fault.

 

I will second the suggestion of a faulty temp sensor but also add a couple other things to check out.

The first being the possibility of a faulty thermostat or also possibly one that is a higher opening temperature then OEM. They come in several ranges and it wouldn't be the first time that a parts counter gave out a wrong part. Buying a faulty part that is brand new happens way more often then you would think as well.

Next I would recommend checking your radiator hoses, specifically the upper hose. If the hose is soft it could be collapsing and restricting coolant flow under certain engine conditions.

I am fairly certain that all of these engines have the cooling fan running off the serpentine belt rather then an electric fan so the possibility of the fan not kicking in would be pretty slim.

 

I took the vehicle to the dealership to get diagnosed because my temp was always going up in the morning when I first drove my car and I am losing coolant. It turns out that its my headgasket (the leak is going into my exhaust) which is the worst possible news...well actually a cracked head or block would be the worst possible news. I am glad I finally have answers and now I debate...do I tackle this myself or do I bite the bullet and have them do it for approx $2000.

It makes sense that the temp was rising because I am getting air from the exhaust in my coolant which is causing air in my system and that air is travelling to the highest point in the engine which is my thermostat, hence why it is getting so hot then when it does open it cools down.

One question I do have...I asked them if it could be the lower intake manifold as they are notorious for going and he told me that there is no way it could be because my oil would be contaminated which it is not...anyone have any thoughts?

 

The oil does not always get contaminated when the lower intake gasket starts to fail. I have replaced these on 6 different 4.3's of various years and of all of them only 2 had the oil contaminated even though all of them were leaking coolant from the gaskets.

If coolant is leaking into the cyl air intake area then having coolant in the exhaust is to be expected and is what happened on 3 of the ones I have changed.

If coolant in the exhaust is the only proof that they have of a blown head gasket then I would suggest you run a leakdown test to determine if that is really what is wrong. Others may have other tests you can run for proving/disproving a blown head gasket before taking it in.

There are many guides floating around the net that can give you step by step instructions and tips for the lower gasket replacement and I would certainly suggest that is more likely then a blown head unless you have let it get into the red zone and stay there often.

 

Thanks for the feedback...I wanted to post what the dealership had found out so anyone interested or with similar problems could view...I see so many posts but I guess once people solve their problems they don't always say what it was...which I really like to know.

The dealership tested my exhaust and found traces of coolant in it....and I was hoping it might be the lower intake but they are saying it is the head gasket and not the intake...however based on the last post I am wondering if maybe they are wrong...that would be great if they are but how can I be sure which it is without taking the engine apart....I do a lot of my own repairs however I am at a loss for what else I can do in regards to tests to tell which one it is....

 

Both problems do have some symptoms in common which can lead to a misdiagnosis. However there are a couple of extra symptoms with a blown head gasket that don't show up with a bad intake gasket that I can think of right off the top of my head.

A general loss of engine power under load, particularly when going up hills as well as some engine chugging and stalling are also often present with a blown head. This is due to a loss of compression from the blown head.

Also I have not yet seen a blown head that didn't have either coolant in the oil or oil in the coolant or both. (not saying it can't happen but I have not seen it yet)

I have also not seen a head that was leaking coolant not have any other symptoms at all besides coolant in the exhaust.

Run compression and leakdown tests on all cylinders and you will have your confirmation one way or the other. I'd hate to see you spend money on a head job if it isn't needed.

How to do a leak down test
http://www.carcraft.com/techarticles...ter/index.html

How to do compression test
http://www.geocities.com/dsmgrrrl/FAQs/compression.htm
(these aren't specifically for the blazer but the process is the same for any engine)

 

I am going to take your advice and hope that it turns out to be the intake. I will say that my intake has a flaw in it, when I went to change the thermostat I was shocked when I noticed that a third of the flange was corroded away. I was able to put a gasket on and some sealet and no leaks...this make me think how bad the rest of the manifold might be and perhaps this is where my problem lies.......I need to get repacement intake and will go to the auto wreckers this weekend seeing how the dealership wants 1900 for a new one. Have you ever seen this problem with the lower intakes?

On a final note I do recall about a month or two ago when I was on a road trip my car was very sluggish going up the mountain....