Need help - Thermostat orientation - PeachParts Mercedes-Benz Forum

eatont9999 · #1 03-17-2012, 05:54 PM

Hi all,

I am rebuilding my coolant system and I need help with installing the thermostat. I need to know if the end with the springs faces the rear of the car or the front of the car when positioned in the thermostat housing. I currently have it facing the rear. The reason I ask is because I started the car up before attaching all the heater hose mess to make sure the thermostat works and it started on its way to 120C before I shut it down. Upper and lower rad hoses are cool but the thermostat housing and passenger side heater hoses are hot.

Please help asap. I want to get this finished today.

I couldn't find any info on the orientation of the thermostat through searching, sorry.

KarTek · #2 03-17-2012, 06:36 PM

The spring always goes toward the engine from a flow perspective. That way it gets the most accurate reading on the engine's temperature.

As far as physical orientation, I can't say. What engine is this?

Also, you probably have an air bubble. That's why it heated up like it did. You can remove the upper radiator hose and fill the engine block from there and that will help purge the bubbles.

However, depending on the engine, the thermostat may be in the block attached to the upper hose and in that case, you can't fill it like that. I'm just guessing though, since I don't know what engine you're working with.

eatont9999 · #3 03-17-2012, 09:03 PM

KarTek, I think you were right about the air bubble. I have an OM617 engine. I installed the spring facing the engine for the reasons you said but I second guessed myself after it heated up. It's running great now. I put in the Zerex G05 and took it for a spin and it didn't get past 100C.

A previous owner either removed the springs from the old thermostat or they are in my engine somewhere because I only found half a thermostat. It looks like someone took it apart for some unknown reason. The car never got over 50C like that.

I replaced every hose except the one that connects the monovalve to the booster pump. I found some heavy duty 1 5/8" hose at O'Reilly Auto for the bypass and it fits perfectly.

I thought getting the monovalve, booster pump and heater hoses out was a royal PITA to get out but that was easy compared to getting it all back in. You really have to plan out your clamp placement or you will find yourself taking things apart just to flip a clamp over.

KarTek · #4 03-17-2012, 10:55 PM

Great, glad to hear it's running well now.

Yak · #5 03-17-2012, 11:54 PM

Did you post the pic in another thread? No guts, hole drilled in it?

I'd guess the PO customized your T-stat. There's a diesel giant site that talks about drilling out the t-stat to get cooler temps. I'd say not necessary, and I think the FSM backs that up; but if it works for some...

eatont9999 · #6 03-18-2012, 04:18 PM

Quote:

Originally Posted by Yak

Did you post the pic in another thread? No guts, hole drilled in it?

I'd guess the PO customized your T-stat. There's a diesel giant site that talks about drilling out the t-stat to get cooler temps. I'd say not necessary, and I think the FSM backs that up; but if it works for some...

Yeah, I posted it in my citric acid flush thread. If one wants cooler temps, then get a cooler stat. There is no reason to gut a thermostat and run one of these cars at 40C. I can only imagine that a cold engine will lose power and MPG because in a Diesel, heat benefits the combustion process. Maybe that's partly why my exhaust smelled rich. I will have to see what it smells like at temp.

Right now, I am running at 90-110C operating temp. It usually stays a hair under the 100C mark. The heat is HOT unlike before where I could only get luke-warm air from the vents.

The monovalve seems to be staying open because even when I have the climate control off, I still get ambient heat flowing when I am driving at higher speeds. I was thinking it could be an outside vent door with a bad dash pod but with the climate control off, I think the monovalve should be closed. Even with the temp selector wheel on max cool, I get hot air.