[SteveKen]

I hope to have my new thermostat sometime this week. It looks like a terrible job to do, especially since I couldn't find any DIY tips on the net or forums.

Once underway, I might try and snap some pictures and do a little step by step.

I have a $10 pirated CD service manual on its way to me, but I'll probably get started without it.

Anyone have any tips before I get started???

 

[wrumbarger]

Dont' know if this is what you are doing?

Thermostat Sensor Change

Evilution - Smart Car Encyclopaedia

 

[Brabus007]

1) Why you changing It...?
2) Be sure to purge the air outta the head when you refill...!

 

[Rustedwrench]

According to smart it is easy. Drain coolant. Remove the right rear inner fender, belt guard and belt. Lower engine. Remove generator and intake manifold and it's right there.

Nothing to it.

Why do you think you need a thermostat?

 

[Rustedwrench]

Dont' know if this is what you are doing?

Thermostat Sensor Change

Evilution - Smart Car Encyclopaedia

No, that is a coolant temperature sensor. The heading is incorrect.

 

[SteveKen]

The symptoms are classic thermostat. I lose heat in the cabin and the temp light comes on for about 5 seconds. then it goes out, then I have heat again. It did this three times on my 25 mile commute home about a month ago and I've parked it ever since and driven my other car.

The coolant was very low and looked like it all came out of the reservoir via the cap, as I see no evidence of coolant loss from anywhere else.

Not sure what else it could be and I don't want to just refill the coolant and chance overheating the engine as-is.

 

[SteveKen]

By all means, please let me know if there's anything I can try or do to keep me from doing this. This seems like a job that I'd be happy to avoid doing.

 

[GoFaster]

Make sure the reservoir pressure cap is sealing properly and holding the correct pressure. Not sure how they are supposed to be tested ... but that is a whole lot easier to replace. And, if you decide to run the engine again, make sure you get the air pockets out.

 

[Brabus007]

Sounds like you were low on fluid the first time, and got a air bubble in the head, and boiled it out.
Were you checking the fluid level EVERY month on the Smart. It would be un-wize not to when owning a Smart Car.
I would refill it, and purge the AIR out of the head, and watch the Tank with the cap off to see if its blowing bubbles (yes, could be head gasket)(No, tighten down the cap and take it for a drive). How cold was it out when this problem happened (anti-freeze up to snuff).

 

[SteveKen]

I must be honest and say no on the checking of the coolant level. Maybe I'll just top it off bleed the head and drive it around to see what happens.

If we need to constantly check the coolant level, where is it going?

Car has 77k miles on it and the coolant has never been changed, btw.

It was below freezing when this happened, too. However, it was warmer in the afternoon when this happened, versus in the morning where it was dead cold from sitting outside overnight.

 

[Brabus007]

In 2008 & 2009 there was problems with scuffing of the coolant hose right where the hose goes over a sharp frame edge, as it heads to the front of the car (factory screw up left many with coolant engine failures)(you must get under there and check that out).
Note: It would be wize for all Smart owners to take a look under their cars for this problem as our cars rack up high miles, and the engine rocks more on old engine mounts...!

 

[Rustedwrench]

Your symptoms are not those of a thermostat fault. It sounds as if you have air in the cooling system. Before throwing any parts at it I would refill the coolant, bleed the air out, run it and keep an eye on it to see what happens.

If there is coolant residue around the cap on the coolant reservoir then either the cap was not tight and/or leaking or you are getting combustion gases in the cooling system from a leaking cylinder head gasket forcing the coolant out.

 

[SteveKen]

Your symptoms are not those of a thermostat fault. It sounds as if you have air in the cooling system. Before throwing any parts at it I would refill the coolant, bleed the air out, run it and keep an eye on it to see what happens.

If there is coolant residue around the cap on the coolant reservoir then either the cap was not tight and/or leaking or you are getting combustion gases in the cooling system from a leaking cylinder head gasket forcing the coolant out.

So is there any test I can perform to verify the head gasket? I can do a compression and leak down test today if it will tell me something.

Does anyone have the compression specs?

 

[wahi]

From my dealer's worksheet on my car, it's 190 for normal.

 

[Brabus007]

So is there any test I can perform to verify the head gasket? I can do a compression and leak down test today if it will tell me something.

Does anyone have the compression specs?

Yes it will show combustion leak into the cooling system (bubbles)...

 

[Rustedwrench]

So is there any test I can perform to verify the head gasket? I can do a compression and leak down test today if it will tell me something.

Does anyone have the compression specs?

Compression specification is 15 bar or 218 psi. Wear limit is approximately 11 bar or 160 psi. As how to test it, think about what may be happening. If there is a leak between the one or more cylinders and the coolant jacket one can test from either one to the other. The coolant system must be full of coolant and free of air. Bear in mind the leak may occur only when hot or cold or in between. More than one test is needed to condemn.

One can put a pressure tester on the coolant reservoir and check for coolant intrusion into the cylinders. Since visibility is poor without a bore-scope one can let the engine sit with the pressure on it for awhile then disconnect the fuel injector electrical connectors and see if coolant sprays out of the spark plug holes when you crank the engine. It may be hard to see unless it is a substantial leak. One could hold a white paper towel in the spark plug holes to catch any coolant, then give it the look and smell test. One can also check for pressure in the cylinder with the cooling system under pressure. It would require a low pressure gauge or a redneck pressure gauge. That would be a balloon or latex glove taped onto your compression tester hose in place of the gauge. If you put pressure on the cooling system and the glove gets a erection and gives you the finger you are screwed. Not to mention insulted.

Since you can only pressure test to 15 to 20 psi a leak may not show up making the results inconclusive. The opposite test is to perform the compression test and test for pressure in the cooling system as above. The cylinder will create more pressure than the cooling system tester, obviously, but due to the distance to the coolant reservoir this may or may not show anything. If the leak is severe you may see bubbles in the coolant or coolant blow out of the reservoir. If so, you are done. And so is it.

 

[SteveKen]

Update.

Since it seems like the definitive diagnosis of the leaking head gasket is too hard to determine, I've done as you suggested:

Refilled the coolant and bled the system at the head and will diligently monitor the coolant level.

I noticed that the reservoir has chambers in it and was able to watch the coolant flowing, etc. with no evidence of bubbling, etc.

I have no driveability or performance (loss of power, etc.) issues that I can tell and the heat is working fine with no intermittent loss of heat as before. I drove the car around for about 30 minutes, checking the coolant about every 10 minutes.

I'll keep an eye on things and report back.

I hope it's just an issue of coolant loss building up over the years without ever refilling it or flushing it.

This spring I'll reflush, change front brakes and rotors, refinish the wheels and get some new tires & valve stems (if possible with the TPMS?).

I just verified my mileage: 73,500

I'm the original owner and have never done anything but change the oil & filter on this car and replaced the tires at 40k. The service indicator blinks -63,500 when I start it up. Lol </ducks>

 

[SteveKen]

Continuing update.

All is good with the coolant level and performance of the engine.

I'm guessing my issue was due to the coolant level, as stated above.

Thanks again.

 

[mattwithcats]

coolant level

I filled mine up to about an inch or two above the "max" line, just a little extra.