I have 78 300d with a turbo expansion tank radiator set up and I need help!

the car used to have the cap on the radiator it self but they don't re-make that style any more so went to the turbo style radiator. the expansion tank, nissen radiator, expansion tank hose, and thermostat (i have tested first before installed) is all new but the water pump is original from the car and radiator cap was replaced year ago from the original radiator.

the issue is the temp is at 200 F and never drops. it has heat from the heater, upper radiator is hot BUT the lower radiator is cold and has no pressure when i squeeze it and the t-stat housing get worm and hot back and forth. any one have a clue??? or is it normal???

The thing to do is replace the thermostat.

Air in the system? Clogged radiator?

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1990 190E 3.0L

I'd go ahead and replace the water pump. I have seen them with the impeller corroded bad enough that they wont pump water.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

What were the symptoms before the rad was changed? Why was the rad changed?

the old one was leaking from the top seam of the rad and the temp was jumping up between 180F and little over 200F when driving around and stay around 180F after 30min drive. did not over heat. installed new t-stat but still did the same thing. just got H20 pump today, have not installed.

is it possible the new radiator is plugged??

If the temperature is staying at 200, you don't have a problem.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

but what is the cause of the cold and no pressure only on lower rad hose?

UP DATE.
installed different maker t-stat, installed H2o pump, and raised the expansion tank higher then the t-stat housing/bleeder and problem solved. temp is normal 175 F ~ 190 F.

have a 91 420 just bought it is over heating has a new radiator went to change the thermostat and it wasn't there got one recommended for the car but doesn't fit

If your car is overheating and there isn't a thermostat, then the thermostat isn't the problem. I would check the fan and water pump. As for your thermostat that doesn't fit, the obvious solution is to get one that does.

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1990 190E 3.0L