Hey guys,

I replaced the hoses and radiator yesterday, as well as the thermostat. The Wahler T-stat seemed to not fit "snug" inside the housing. I took the old one out a few days ago so I am not 100% sure how the t-stat fit inside the housing.

The problem that I am having now is the coolant is not getting to the block, so I'm guessing the t-stat is not opening, even at 100C. What would cause this? I ran water through the system prior to adding the t-stat and everything flowed smoothly.

Sorry if this is a stupid question, but does the entire system need to be pressurized in order for the t-stat to open? I was adding coolant like I normally would in a modern car, by adding the coolant with the radiator cap open and waiting for it to bubble down, then adding more. Maybe the 300SD is different and needs to be closed while running the engine to get the coolant to flow to the block.

I'm going to try to keep the cap closed at startup and see if that open the t-stat, but I figured during my break at work I would ask here and see if anyone would have any suggestions that I could try.

BTW, I have not tried to test the t-stat with boiling water, figured I'd exhaust other tries before doing that since it's a brand new part.

Thanks!

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1981 Mercedes 300SD - 186k miles

1978 Corvette Pace Car - 21k miles

2006 Mazdaspeed 6 - 56k miles

All ways points away from engine. Tstat opens based on coolant temp.

I forget whether there is a gasket that goes on the Tstat itself or only between the engine and neck.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

You probably have air in the head. You might try removing the upper radiator hose from the radiator, then adding coolant via the hose.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

You may have to burp the engine in order to get all the air out of the block. If you can park the car with its nose up, try pouring coolant into the top radiator hose with the engine off. I would also put the heater control in the max position. Good luck

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96 E300d

Thanks guys I'll try those tonight and report back!

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1981 Mercedes 300SD - 186k miles

1978 Corvette Pace Car - 21k miles

2006 Mazdaspeed 6 - 56k miles

If you don't have heat from the heater, the head (and water pump) is air bound.

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'83 300D, 126K miles.

Stupid me. I didn't have the rubber seal around the thermostat correctly. Once I did that, I parked the car on a hill and let it run with the heat blowing on high. Everything seems to be running smoothly now!

Sent from my SAMSUNG-SM-G900A using Tapatalk

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1981 Mercedes 300SD - 186k miles

1978 Corvette Pace Car - 21k miles

2006 Mazdaspeed 6 - 56k miles

Cool, congrats I was going to suggest pulling it off and taking a look. Even see the thermostat go in backwards on these, it's easy to do.

Parked it on a hill, facing uphill or down? Does this help with air pockets?

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1983 W123 300TD US spec Turbo engine, with Euro bumpers and manual climate control, and manual transmission.

Parking the car with the front end facing up. If you disconnect the top radiator hose from the radiator, it will usually allow any air to escape as you refill the system.

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96 E300d