Om603 Solving temp swings - Page 2 - PeachParts Mercedes-Benz Forum

dieseldiehard · #16 07-24-2019, 12:06 PM

this is all very interesting, I have a #14 head and its been replaced when I bought the car due to the PO walking away from it when he learned the shop wanted $1400 to replace the head (they also lost the original head when some metal hawk stole it off the shop floor). I got it as a mechanics lien and put a used head on it (after a valve job etc.) since then I've put over 40K miles on it and the block now has 305K on it.
So far the #14 head is working fine but I have a later head available in case.
Before I took on the cooling system mods described I would install an electric fan, I've been thinking of that but have other projects always getting in the way.
Oh, and a comment on temp fluctuations.
My OM604 cooling has temp fluctuations that are hardly anything compared to the OM603 but oddly my M104 seems to have a lot of temp variations, the engines use almost the same block and I assume the cooling systems are similar but I haven't really examined them closely. The diesel runs cooler of course. I'd like to take on the M104 and install an electric fan before I work on the '87 diesel.
DDH

tjts1 · #17 07-24-2019, 12:40 PM

Quote:

Originally Posted by Mxfrank

Actually, he didn't, because both ends of that hose are on the high side of the pump. If the hose flowed even a little, it would either be moving the very hottest coolant to the rear port, or it would be moving cool coolant away from the rear and into the radiator. The one thing it absolutely wouldn't accomplish is to add cool fluid to the rear. I'm guessing that only a small amount of coolant actually flows through that hose, and only when the thermostat is closed.

No, that's incorrect. Those of us living in hot climates have been dealing with this problem for years. What the OP did is spot on and proven by his results.

martureo · #18 07-24-2019, 03:32 PM

Quote:

Originally Posted by tjts1

No, that's incorrect. Those of us living in hot climates have been dealing with this problem for years. What the OP did is spot on and proven by his results.

I'm with MxFrank on this one. But as a check I'd want to see a flow meter or temp gauge on this additional line. My guess is that the line is flowing from the rear cylinders into the mixing area rather than providing cooler water to the rear cylinders.

97 SL320 · #19 07-24-2019, 05:09 PM

Quote:

Originally Posted by Mxfrank

This allows the ECU to implement a dynamic temperature range that's correct for each operating condition. "Normal" may be anywhere from 170-240F. So no gauges for you.

Can you say altering engine temps to control emissions on the test rollers then changing the operating temps in normal use so as not to cook the engine in the long term?

Quote:

Originally Posted by Mxfrank

97: I can't put my finger on the flow diagram at the moment. Coolant enters a blending chamber from the bypass, heater return and radiator. This is where the thermostat lives, reacting to the blended temp. From there it enters the pump inlet, and is pumped into a gallery along the right side of the block, and from there distributed through the block and head. The block drain is on the right side water gallery, all the way at the back. Here's the blend chamber:

Thanks. It looks like the temp sender in the pic is measuring cooled water after it leaves the radiator and / or suction side of the pump, this won't give an accurate representation of maximum engine temps. With the original stat gone, the bypass is in constant operation adding to the mess.

I'd be very interested in temps just prior to the new stat and at the radiator inlet, these are the temps that really matter.

97 SL320 · #20 07-24-2019, 05:16 PM

Quote:

Originally Posted by dieseldiehard

My OM604 cooling has temp fluctuations that are hardly anything compared to the OM603 but oddly my M104 seems to have a lot of temp variations, the engines use almost the same block and I assume the cooling systems are similar but I haven't really examined them closely.

Have you pulled / inspected the M104 stat?

See my post 12 and 14 95 C280 Overheating

The M104 uses a stat that regulates water going to the rad rather than coming from the rad like the OM.

h3ffe · #21 07-24-2019, 10:39 PM

Can you elaborate? MxFrank's flow picture seems to indicate that if the line is fitted to the port on the housing that dieselmeken drilled and tapped, the flow would push mixed coolant through the water pump scroll and then theoretically also into this hose.

If the line is flowing from the rear cylinders into the mixing area as you suggest, then that pressure differential would promote cooling to the rear cylinders by pulling coolant through the front cylinders to the rear faster.

It seems to me that one way or another this mod improves cooling. Dieselmeken isn't exactly a novice with these engines, either.

I'd love more information if you, SL, or MxFrank can provide some, as I'm no expert. Thanks to all for engaging in a valuable discussion and sharing information!

Quote:

Originally Posted by martureo

I'm with MxFrank on this one. But as a check I'd want to see a flow meter or temp gauge on this additional line. My guess is that the line is flowing from the rear cylinders into the mixing area rather than providing cooler water to the rear cylinders.

JonW124 · #22 07-25-2019, 01:14 AM

Quote:

Originally Posted by martureo

I'm with MxFrank on this one. But as a check I'd want to see a flow meter or temp gauge on this additional line. My guess is that the line is flowing from the rear cylinders into the mixing area rather than providing cooler water to the rear cylinders.

The water pump is pushing water directly into that tapped line coming off the thermostat housing and pushing water to the rear cylinders. I've read it's supposed to help avoid hot spots on the rear cylinders and since it's pushing water through from the cold side I'm sure that helps as well. I didn't come up with this mod but it has been put to use for many years with the Super Diesel guys and multiple company across the pond sell it for god reason. It's been tested so I don't really need to question or wonder if it works.

JonW124 · #23 07-25-2019, 01:58 AM

Quote:

Originally Posted by Mxfrank

Actually, he didn't, because both ends of that hose are on the high side of the pump. If the hose flowed even a little, it would either be moving the very hottest coolant to the rear port, or it would be moving cool coolant away from the rear and into the radiator. The one thing it absolutely wouldn't accomplish is to add cool fluid to the rear. I'm guessing that only a small amount of coolant actually flows through that hose, and only when the thermostat is closed.

This is different from the mod in the youtube video, because in the video, the rear port is connected directly to the water pump outlet. That would have the effect of diverting a bit more flow to the rear of the block.

As I explained, the temp swings are an inevitable consequence of having the thermostat on the cool side. The thermostat has to be slow-reacting, or the system wouldn't work at all. You can produce more stable temperatures by engaging the fans earlier, but it's tough to get temps rock steady.

I think what you're looking for here is a strategic flow approach, as has been attempted on some Jaguar engines. This entailed sizing the ports in the head to restrict flow to the front cylinders, which allows more flow to the rear. It can be accomplished with a special head gasket, so it's possible to work out a retrofit. But this hose is just ludicrous.

Many modern cars use MAP controlled thermostats, where the "natural" temperature of the thermostat is 240F, and it's artificially heated with a resistance coil. This allows the ECU to implement a dynamic temperature range that's correct for each operating condition. "Normal" may be anywhere from 170-240F. So no gauges for you.

Personally, I prefer a steady temperature, as fluctuating temperature means fluctuating pressure, which eventually fatigues the radiator and heater core. But that's not where things are going.

97: I can't put my finger on the flow diagram at the moment. Coolant enters a blending chamber from the bypass, heater return and radiator. This is where the thermostat lives, reacting to the blended temp. From there it enters the pump inlet, and is pumped into a gallery along the right side of the block, and from there distributed through the block and head. The block drain is on the right side water gallery, all the way at the back. Here's the blend chamber:

I do have the same mod as posted in the Youtube video. Before I changed the position of the thermostat all my cooling system was replaced (trying to cure these temp swings) only to get the same results. I tired 2 different brand radiators. Installed the Om606 water pump and pulley along with Om606 fan and clutch (which don't help anything but idle or slow speed temps). I would drive up a grade or hill in San Diego and my temp would go from 82C to just under 100C rapidly. So I'd pull over and check the radiator. Half would still be relatively cold like the coolant wasn't flowing enough. I tried 4 different thermostats with the same results thinking they could be sticking or broke. After the thermostat relocation my radiator has even heat through out very quickly. The engine gets up to temp right away and stays consistent no matter how I'm driving now.

So my question would be why you believe the temp swings before where real and "normal" but can't believe the stable temps I'm seeing now aren't accurate with the same sensor?

Also the smaller Chevy thermostat works great cooling 500 plus cubic inch Chevy engines. It maybe smaller than the Mercedes T-stat but I think it can handle a 3.0 liter engine producing 150 hp.

Here's a pic of my thermostat housing.

IMG_3166 by jon allie, on Flickr

97 SL320 · #24 07-25-2019, 06:42 AM

With this new pic not in the original post, there would be some coolant flow to the rear but I'd want to see the action of a flow indicator.

The real question is, that newly drilled / tapped boss is a factory port for something, what was it for? Maybe an oil cooler?

If for a canister type block heater, that relies on thermosiphon and is only active with the engine off. These canister heaters generally have a check valve to prevent flow while the engine is in operation.

JonW124 · #25 07-25-2019, 11:08 AM

Quote:

Originally Posted by 97 SL320

With this new pic not in the original post, there would be some coolant flow to the rear but I'd want to see the action of a flow indicator.

The real question is, that newly drilled / tapped boss is a factory port for something, what was it for? Maybe an oil cooler?

If for a canister type block heater, that relies on thermosiphon and is only active with the engine off. These canister heaters generally have a check valve to prevent flow while the engine is in operation.

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I've never seen the spot on the Om603 that I drilled and tapped ever be used from the factory. So I'm not sure what they casted the housing like that for. I highly doubt it flows a ton but I'm sure that it flows enough to help circulate the water in the rear cylinders. Which is where both my Om603 #14 heads cracked previously. Not to mention I found 7 Om603's in the junk yards here looking for another used head and they were all cracked in the same rear cylinders.

martureo · #26 07-25-2019, 02:52 PM

Quote:

Originally Posted by JonW124

...

Also the smaller Chevy thermostat works great cooling 500 plus cubic inch Chevy engines. It maybe smaller than the Mercedes T-stat but I think it can handle a 3.0 liter engine producing 150 hp.

...

I don't think is this an apples to apples comparison. Diesel engines produce more internal heat energy than gasoline engines, on that alone I'd think that that the cooling systems on a diesel would be greater than that of a comparable gasoline engine.

tjts1 · #27 07-25-2019, 03:14 PM

X

Quote:

Originally Posted by JonW124

I do have the same mod as posted in the Youtube video. Before I changed the position of the thermostat all my cooling system was replaced (trying to cure these temp swings) only to get the same results. I tired 2 different brand radiators. Installed the Om606 water pump and pulley along with Om606 fan and clutch (which don't help anything but idle or slow speed temps). I would drive up a grade or hill in San Diego and my temp would go from 82C to just under 100C rapidly. So I'd pull over and check the radiator. Half would still be relatively cold like the coolant wasn't flowing enough. I tried 4 different thermostats with the same results thinking they could be sticking or broke. After the thermostat relocation my radiator has even heat through out very quickly. The engine gets up to temp right away and stays consistent no matter how I'm driving now.

I do not have that problem with the colder BMW M20 thermostat and electric fans. AC on, long hill climbs, sitting in traffic etc the temp gauge never exceeds 90c.

JonW124 · #28 07-25-2019, 11:54 PM

Quote:

Originally Posted by tjts1

X
I do not have that problem with the colder BMW M20 thermostat and electric fans. AC on, long hill climbs, sitting in traffic etc the temp gauge never exceeds 90c.

I ran a colder Bmw thermostat and it did helped keep temps in check and most consistent compare to the normal temp Mercedes T-Stat's. What I didn't like was how long it would take for the engine to warm up. And in the winter the car would never be get to operating temp and using the heater would make it drop to 75C.

With the new thermostat setup its nice to be able to run a hotter thermostat so the car is up to temp within 2 minutes.

JonW124 · #29 07-26-2019, 12:01 AM

Quote:

Originally Posted by martureo

I don't think is this an apples to apples comparison. Diesel engines produce more internal heat energy than gasoline engines, on that alone I'd think that that the cooling systems on a diesel would be greater than that of a comparable gasoline engine.

I owned a 540 cubic chevy engine that used the same thermostat I'm using in my Om603 now. My 540 BBC made 685 hp to the wheels and creates a ton of heat. I understand diesel engines create a lot of heat and the turbo really adds to that. But I drag raced that engine and drove it hard and that small thermostat had no issues. The point I was trying to make about the Thermostat size is that it doesn't matter if the cooling system is efficient.

tjts1 · #30 07-26-2019, 01:34 AM

Quote:

Originally Posted by JonW124

I ran a colder Bmw thermostat and it did helped keep temps in check and most consistent compare to the normal temp Mercedes T-Stat's. What I didn't like was how long it would take for the engine to warm up. And in the winter the car would never be get to operating temp and using the heater would make it drop to 75C.

I've never had that problem but I only experienced tepm down to 28f. We don't have real winter. In a real winter situation its easy enough to block off 1/2 the grill.