Smart 450 Cooling System

[tolsen 630]

It is possible we are loosing some heat from heater matrix circuit to the radiator via expansion tank.

In the absence of a suitable cooling system diagram I have added a collection of some self-explanatory images showing the routing of coolant through the system:

There is a small valve with a blue plastic ball at top of elbow (that connects to radiator) inside the expansion tank. Any coolant flowing through this valve is loosing valuable heat to radiator. You can see this valve by removing filler cap and sucking out some coolant. I think it is worth while investigating this potential heat leak further. Check it out folks!

[Alex 21]

The return flow from heater goes through the expansion tank?! How not-smart. That should return direct to to water pump. Even without any leakage to radiator there is still heat loss, plus the additional volume of coolant to be heated.Looking forward to your ingenious solution, Tolsen!

[bilgladstone 13]

Thank you once again for another interesting detailed look at the smart systems.No wonder they never issued a tech manual... anybody would look at it and say WTF!?Bil

[bilgladstone 13]

I wonder if a restrictor at one of these points, where one has easier access than at the engine, might serve the same purpose as your restrictor plug, TK?

[tolsen 630]

I wonder if a restrictor at one of these points, where one has easier access than at the engine, might serve the same purpose as your restrictor plug, TK?

Restrictor plug in its recommended position serves two main purposes and can't be fitted in any different location except perhaps at thermostat itself if redesigned:A. Increases flow through heater matrix so potentially more heat in cabin.B. Increases back pressure over thermostat so the internal brass check valve seals shut thereby loosing less valuable heat to radiator.Volume of coolant system of the Cdi is 4.5 litres (Petrol 160 engine 4.2 litres). Those that read my first post will have noticed (Alex did) that the volume of coolant circulated to heater matrix is unecessarily large. Engine will get quicker up to operating temperature if this volume can be substanially reduced. Its like heating water in a kettle. No need to fill the kettle full if you only need one cup.A quick calc this morning indicates that volume of coolant circulated to heater matrix can easily be reduced by 1.5 litres.This is how I intend to achieve this reduction:1) Run return from heater matrix in a rubber hose through tunnel (do not yet know if there is space) or in double bottom space and T in just before V - piece at water pump. A separate bleed line connected as near as possible to heater matrix return outlet is required to get air out of the circuit. 2) Blank off both heater matrix connections to expansion bottle.3) Possibly remove the blue ball fitted in the valve inside expansion bottle. I will know if this is required once I have looked further into the operation of this valve.Running return from heater matix as 1) above but T-ing in at the current point on radiator to water pump return line will reduce volume of circulated coolant by 1.2 litres which may still be quite an improvement. What are your thoughts folks? Who is going to try this mod first?

[Pingu 0]

Thank you Tolsen, for continuing on solving this mystery. Since you can access the heater lines at the expansion bottle, can you install a valve and shut off or severely restrict flow through the heater matrix? Would this cause a problem with the water pump? The heater matrix circuit acts like it has a huge hidden radiator. Another thing that I notice is that the engine cools down very quickly after it is shut down. That seems to indicate that flow in the heater matrix circuit continues after shutdown.

[tolsen 630]

Thank you Tolsen, for continuing on solving this mystery. Since you can access the heater lines at the expansion bottle, can you install a valve and shut off or severely restrict flow through the heater matrix? Would this cause a problem with the water pump? The heater matrix circuit acts like it has a huge hidden radiator. Another thing that I notice is that the engine cools down very quickly after it is shut down. That seems to indicate that flow in the heater matrix circuit continues after shutdown.

You can clamp flat the most accessable heater matrix hose that connects to top of expansion tank, go for a test run and check how fast engine gets up to operating temperature. Mits and hat recommended as there won't be much heat in cabin. Water pump will still be getting coolant from the bypass so no problem there - coolant will only be circulating around the engine.

[Alex 21]

Another potential problem is that with the heater return into the top of the expansion tank, it splashes into the coolant and causes bubbles to be drawn into the system. Especially if the coolant level is just a bit low. This may be the reason I've heard of airlocks developing. A filled system doesn't "make" air, it comes from somewhere.

[tolsen 630]

Yes that may be the source of air Alex but expansion tank should auto bleed air out when level is right.By the way, I have just done the test I suggested in post #7 above by clamping flat the outlet hose from heater matrix restricting flow to nil. Engine was up to 3 blobs after 3 km of moderate driving stuck behind a fully laden lorry. Ambient temperature was +4 C. It was freezing cold inside my Smart. I can assure you, there is not much heat coming from that electric heater.I think I will proceed with modifying the cooling system pretty soon. Got to tidy up my garage first as too cold, wet and windy working outside.

[Pingu 0]

Thank you for being a man of action. I have been speculating on this for 3 years, but never actually did it.I have never got 3 blobs in 3 km on the hottest summer day at moderate speeds, so the heater circuit sure takes the heat out of the engine. From your test, the engine block, the coolant in the engine block, and the coolant in the radiator were heated up quickly. That leaves the coolant in the heater lines and heater matrix.I have tried to decrease engine warm up time by shutting of the airflow through the heater matrix. i.e by moving the temperature lever to the cool air position. I found that engine warm up is only changed marginally.I am surprised that a Scot would find 4°C to be cold. At least the wind wasn't blowing inside the car! lol (My ancestry is half Scottish and half Scandanavian.)

Edited November 9, 2010 by Pingu

[bilgladstone 13]

Also 4C here this morning. My usual 87.5km "commute" saw the coolant temperature rise to 65 degrees. The way home - 8.7Km takes me past my mailbox - saw 70 degrees.So that's it for this year. Even on longer trips, I probably won't see 3 blobs again until the spring of 2011.Bil

[Francesco 71]

I'm not sure I'll be using Kane's method for lowering the power module again, as you'll remember not long after I completed the mod using it my car was diagnosed as having a broken motor mount.So if you make strides at a solution and require beta testers I'll be sure to inquire with my dealership about getting comped a set of lowering pins.

[MikeT 747]

I am sort of thinking that 200K km (or less than half that in MTL) would be a good time to change engine mounts anyway, as a precaution!

[Francesco 71]

Continuing OT: with the non-stop stop-and-go traffic here and the world's worst roads, I would suggest the smart's mounts are good for 75K or less here. I had one changed at 60K, and I'm nearing 74 now.

[tolsen 630]

Continuing OT: with the non-stop stop-and-go traffic here and the world's worst roads, I would suggest the smart's mounts are good for 75K or less here. I had one changed at 60K, and I'm nearing 74 now.

My engine mounts are no longer as good as they once were. Engine seems to vibrate more at idle. My Smart has only clocked 147K (km) but the Scottish roads are very rough and uneven, not smooth like on the Continent and in Scandinavia.I suppose the ride could be greatly improved by fitting standard tyres perhaps 80 profile both front and rear. That is a mod I have up my sleeve, fitting 165/80-13 or similar tyres on steel rims with roll diameter matching the original Smart wheels.

[tolsen 630]

I was wondering whether Smart had done some smart coolant system improvements when designing the new 451 Cdi. Regrettably, the thermostat and coolant flow path is very similar or identical to the 450, so I assume it will suffer the same problems with poor cabin heat and slow getting up to operating temperature. Here are some images borrowed from an online Russian Mercedes EPC system showing 451 Cdi cooling system:

Thermostat and water pump.

Coolant pipes, hoses and expansion tank.

Heater and airconditioning unit.

Radiator, condenser and cooling fan.

There is a noticable improvement in quality and detail of line drawings.

Edited December 2, 2010 by tolsen

[Some Guy 0]

This is a bit over my head. :scratch:If you could bear with me here, just to see if I'm even on the right page... what's essentially being discussed is getting rid of the magenta arrows on the fourth picture?

[bilgladstone 13]

This is a bit over my head. :scratch:If you could bear with me here, just to see if I'm even on the right page... what's essentially being discussed is getting rid of the magenta arrows on the fourth picture?

Or maybe just a partial bypass, reducing the flow through the expansion chamber?B

[tolsen 630]

This is a bit over my head.

If you could bear with me here, just to see if I'm even on the right page... what's essentially being discussed is getting rid of the magenta arrows on the fourth picture?

Yes that is my plan. Piping the outlet from heater matrix straight into radiator return pipe thereby reducing volume of coolant (by 40% perhaps) that need be heated when engine is warming up. I am slightly behind schedule on this modification. Partly because I am still waiting on a special tool to arrive. Smart used some special hose clips named CLIC-E and CLIC-R. I wish to reuse these clips but need a special tool which looks like this:

Sealey Model No. VS1661 shown. I ordered an identical Bergen tool as a lot cheaper.

The other reason why I am late is that I am preparing for a long cold winter. I transported all this wood by Smart in 3 loads:

Perhaps a small wood burning stove in your Smart will keep you warm?

PS. Having trouble splitting some redwood logs. Is there a special trick to it or is my axe too light?

[Francesco 71]

A wedge and a big hammer. That's all I got.

[MightyMouseTech 0]

To try and improve the heat on my car, one of the things I was going to try this winter was adding insulation meant for home hot water pipes over the alluminum lines that run underneath the car from back to front. Figure that would prevent the water from cooling off in it's travels.

Part # 100 in this pic...

Edited November 19, 2010 by MightyMouseTech

[Francesco 71]

Will that alleviate some of the squeaky chatter that happens at start-up until the pipes warm up? Mine sounds like I have a trapped squirrel in there until well into the first blob when it's below freezing out.

[tolsen 630]

To try and improve the heat on my car, one of the things I was going to try this winter was adding insulation meant for home hot water pipes over the alluminum lines that run underneath the car from back to front. Figure that would prevent the water from cooling off in it's travels.

Part # 100 in this pic...

I shall look into if that is possible when I remove radiator. I am also concerned that the alu pipes may chafe at each end leading to an unwanted leak at the most inconvenient time. Got all my wood cleaved and neatly stacked hence can work on the Smart all day tomorrow. Thanks for the tip regarding cleaving Sameguy. What I need is a proper cleaving axe I think.

[Pingu 0]

I shall look into if that is possible when I remove radiator. I am also concerned that the alu pipes may chafe at each end leading to an unwanted leak at the most inconvenient time. Got all my wood cleaved and neatly stacked hence can work on the Smart all day tomorrow. Thanks for the tip regarding cleaving Sameguy. What I need is a proper cleaving axe I think.

I agree that the best for splitting the "rounds" of your wood is splitting wedges and a sledge hammer. I needed two wedges for when I got one stuck and buried in the wood block.I don't understand the smart cooling system. Does the blue ball in the expansion tank provide the pressurization of the system, and the vaccum relief? If the returns from the heater matrix dump into the expansion tank, is that circuit at atmospheric pressure? I see that the 2 expansion tanks are joined with a small hole.

[tolsen 630]

I don't understand the smart cooling system. Does the blue ball in the expansion tank provide the pressurization of the system, and the vaccum relief? If the returns from the heater matrix dump into the expansion tank, is that circuit at atmospheric pressure? I see that the 2 expansion tanks are joined with a small hole.

It will be a lot clearer tomorrow when I will remove and inspect that expansion tank. I think the blue ball forms part of a non return valve that is supposed to prevent hot coolant from heater matrix leaking to radiator.