Bought bosch aquatak 100 pressure washer. No manual or instructions in box. Store bought at cannot help.

It sounds like there may be an issue with your Bosch Aquatak 100 pressure washer. Here are a few possible causes of the symptoms you described:

1. Clogged nozzle: If the nozzle at the end of the pressure washer wand is clogged, it can cause the pressure to drop and the motor to continue running even when you release the trigger. Try cleaning the nozzle with a needle or a thin wire to remove any debris that may be blocking the flow of water.
2. Worn pump seals: If the seals in the pump are worn, it can cause a loss of pressure and the motor to continue running. You may need to have the pump seals replaced by a qualified repair technician.
3. Stuck unloader valve: The unloader valve is responsible for regulating the flow of water through the pump. If the valve is stuck, it can cause the pressure to drop and the motor to continue running. You may need to have the unloader valve repaired or replaced by a qualified repair technician.
4. Other issues: There could be other issues with the pressure washer that are causing the symptoms you described. For example, there may be a problem with the motor itself or with the electrical connections. In this case, it is best to seek the help of a qualified repair technician who can diagnose and fix the problem.

I hope this information is helpful. If you have any further questions or need additional assistance, don't hesitate to ask.

Sounds like you have a seal gone in the pump or a blockage.

The link has changed in the meantime i see
You can use every EP zinc-free hydraulic oil what you want for it PERLUS ZF46 is a very good alternative

does the motor have rust in it??the motor can be replaced

remove pressure nozzle or use low pressure nozzle only for shampoo

clean water filter out, not enough water coming out to cool the motor

First off check your pressure wand / water nozzle make sure it's clean. if that doesn't help then it could be your water pump.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/anthony_e4f197748c31eabd

Check to make sure the outlet (power supply) is energized. This piece of equipment is supposed to be used on a ground-fault protected circuit, so make sure the ground-fault on the outlet didn't trip or the circuit breaker (fuse) at the electric panel did not trip (or blow)
Check to make sure you are going through the proper starting procedures as outlined in your user's manual on page 8.
Follow the troubleshooting tips on page 10 of the user's manual.
Beyond that, Bosch requires that you have your power washer repaired at an authorized / qualified repair center.
I did locate a web site that shows an exploded parts view of the pressure washer, if that helps. http://www.magic-parts.co.uk/acatalog/BOSCH-Aquatak-1200-Plus.php
In case you don't have a user's manual, you can view it at: http://www.manualslib.com/manual/537062/Bosch-Aquatak-110.html#manual
Best wishes on your project.

need to clear out your total inlet system and flush the pump out if needed and install either inline filter or screen

nothing to worry about could be due to water intake,wear on nozzle or just the gauge