overheating question

This is going to seem like a very dumb question but I'm going to risk asking it. My temp gauge isn't working right now. What would be a telltale sign that the vehicle is overheating? I picture smoke coming from the engine and the car being immobilized. Are there any not so obvious signs I should look for? I recently changed a heater control valve and I see today the reservoir isn't at the cold line. I don't see any evidence of the coolant leaking like it was before I changed the valve. Being the paranoid person I am, I'm now thinking blown head gasket and wondering if the car overheated and I didn't pick up on it. I may be jumping the gun but that's my fear. I'm going to check the oil when I can (not driving it now) I looked for bubbles in the radiator which I saw but also wonder if that could be air in the system. The van doesn't seem to be running poor and the only "smoke" is see from the tailpipe is steam at startup. I do get a faint smell of coolant in the cabin but it's not constant.

Thanks

Obvious signs would be steam coming from the engine compartment. If your engine overheats, the coolant would boil and make big clouds of steam.

There is a chance that mild overheating would occur before the coolant boiling. In that case you should notice reduced power and excessive knocking.

Well I checked the oil and it does seem to be thin and discolored. What I thought was steam does appear to be smoke and the coolant keeps dropping but not on the floor. So this will be an expensive lesson learned. Anything else I should replace while the head gasket is being done?

Hi,
It would be quite simple & inexpensive to replace the temperature sensor and/ or gauge. It will be much more expensive to overheat your engine and replace it....

That I'm definitely going to change. Was going to do that anyway and unfortunately this happened before I could.

If you are having a shop do the head gaskets, have them send the heads out to a machine shop to check for cracks and warps.

It is a VERY good idea to change the valve seals. For many years, older small block chevy V8's were known for leaking seals which led to modest oil burning. I am not sure if your year was so affected, but if it is, its much easier to change the seals with the heads off.

Finally, it may be an idea to go for rebuilt heads, which includes resurfaced valves and seats, decent guides, new seals and a check for cracks and warps, so you know everything on them is good.

I'm still going to do a compression test and block test once I can get to autozone to rent the tools. I just pulled the dipstick again hoping my eyes deceived me in that area. The oil looked normal. It's been sitting since sun. If coolant is mixing in the oil, would the oil on the dipstick still be indicative of that days later?

If you are having a shop do the head gaskets, have them send the heads out to a machine shop to check for cracks and warps.

It is a VERY good idea to change the valve seals. For many years, older small block chevy V8's were known for leaking seals which led to modest oil burning. I am not sure if your year was so affected, but if it is, its much easier to change the seals with the heads off.

Finally, it may be an idea to go for rebuilt heads, which includes resurfaced valves and seats, decent guides, new seals and a check for cracks and warps, so you know everything on them is good.

If getting rebuilt heads is what I do, any tips on what to look for? I came upon a site called headsonly.com aka cylinder heads international which had "decent" prices.

Rebuild your actual heads so long as no cracks are found. Do not go for trade-ins or swaps imho

There are a bewildering number of small block heads made over the decades. Many will physically bolt on to your engine but may have subtle differences that may affect performance. Rebuilding your actual heads ensures you have the correct ones. Most major urban centers have engine rebuild shops that can do a set of heads for you.

Also, coolant mixed in the oil will make the oil look like a chocolate milkshake for a long time. If the engine oil looks like oil after running the engine briefly and not a Dairy Queen product you don't have significant amounts of coolant in the oil.

im pretty sure coolant goes to the bottom of the pan

I'm looking for a shop to take the van to. Any suggestions on what to look for? A small independent garage or service center like Firestone?

Thanks

thankfully it wasn't the head gasket. The shop i took it to said it was the heater core and replaced it. I may have to bring it back though. The heat only seems to get "hot" when i'm driving as opposed to idling. any idea what that may be?

thanks

in addition to the temp gauge not working, the oil gauge goes bonkers. check it out

Both are while idling and the first video i put it into D

http://i63.photobucket.com/albums/h151/livewire1568/Van/th_VIDEO0006.jpg (http://s63.photobucket.com/albums/h151/livewire1568/Van/?action=view&current=VIDEO0006.mp4)

http://i63.photobucket.com/albums/h151/livewire1568/Van/th_VIDEO0008.jpg (http://s63.photobucket.com/albums/h151/livewire1568/Van/?action=view&current=VIDEO0008.mp4)

thankfully it wasn't the head gasket. The shop i took it to said it was the heater core and replaced it. I may have to bring it back though. The heat only seems to get "hot" when i'm driving as opposed to idling. any idea what that may be?

thanks

When one does a heater core job it is sometimes hard to initially get all the air out of the cooling system. This leads to not having heat at idle. Just top off the coolant level and keep an eye on it for a few days. Top off at the radiator only when the engine is cold. It may take a few days to get all the air out.

yeah I would guess you have air trapped in the system.