How would you diagnose this problem?

Body: W124 Year: 1987 Engine: Diesel (says 2.5 Turbo on the trunk lid) L6
The problem: When I brake, though sometimes even sitting still but especially when braking, I hear a loud clanking under the hood.
Sounds like the fan blade hitting something. The car has a replacement Nissen radiator. I cannot see any damage to the radiator but two blades show edge wear.
What would you check? I can't find any looseness in the fan clutch. Maybe engine mounts? I'm in a quandry. Just replaced the radiator and don't want to have to do it again. The previous radiator was the same Nissen replacement model. They appear thicker than the original Behr, but unfortunately I don't have the original to compare. Can anyone provide me the thickness of their radiator?
Again, I am in a quandry on this one and don't want to drive the car until it is fixed correctly.
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I would say the engine mount might be the cause.
Check the fan clutch to see if there is any bearing play that might let your fan blade wobble.
Check the fan shroud and make sure it is mounted correctly, the two tabs on the bottom goes in the slot of the radiator.
Make sure th radiator is mounted correctly... Any front end accident on this car? (that could push the radiator inward)
Last thing... if the cooling fan blade is plastic, make sure it is not cracked
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Does yours have the original radiator? If so, can you measure its thickness?
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Yes, mine is original. I have changed many radiator and there is no physical difference between them. I'll take some measurement for you.
I know Nissen radiators... I used three of them already for three different cars. They are good radiators.
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Motor mount(s) collapsed..
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me wrote:

Sounds likely. My GF once shifted my Saab 9-3 from 4th into 2nd (stick shift) at faiely high speed which tore the rear motor mount apart. The result was a loud cranking under the hood whenever I drove backwards.
X.
(kept the GF but switched to MB automatics)
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I would say front springs.
They tend to break close to the ends, and when load changes (by breaking etc.) the broken ends will rub against each other, often resulting in loud clanks.
Awfully many drive around with broken springs without knowing it.
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The fan shroud may be out of adjustment. If yours is like my W123, the shroud mounting points on top have ribs that interlock with ribs on the radiator. This allows for about 15 mm of up and down adjustment. Just remove the clip and move as necessary then re-install the clip.
Check to make sure the shroud is not broken.

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Success!
Today I completed the motor mount swap and all is well. The old mounts from the left left (driver's) side wasn't really bad but the right (passenger) had noticable flex. But I replaced both anyway.
These mounts don't "split" like some other vehicles' because they're encassed in a metal can. That may allow them to last longer or otherwise keep them from flexing as much.
So ... does anyone here repair radiators ... I got one for sale that needs repair. ;-)
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