This is for an 81 300SD but I do have two others with the same (917.xxx) engines and was wondering just how important this bypass pipe is. The reason I'm asking is, I cannot find the bonjoe(hollow) bolts to replace one that I heavy-handed and stripped out. Now I have a slightly bigger hole and threaded it with a M8x1.0 tap but the good bolt just slides into and out with slight drag. I will probably repair the hole that stripped and get a new bolt but I was just wondering about this in the meantime.

__________________
1981 300SD

Would like to see the damage area if possible.

__________________
ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

I didn't take a pic of the area since it is a little hard to get my OLD digital camera there to take it along with my fat head to see what I was taking a picture of. The hole that is stripped is the one in the cylinder head on the bypass pipe from the block. It's not damaged too bad that I can't repair it but I was just wondering if I was to plug both the block and the head holes and discard the pipe if it would be detrimental to the engine and its performance. Also the hollow bolt for the pipe is what I heavy handed and just twisted it off.

I attached a pic of one of the other engines of the bolt and bypass pipe that I am talking about.

Attached Thumbnails

 

__________________
1981 300SD

I may be wrong, but that looks like the oil line to the head.
If so, it is most definately needed!

To close, back off a couple inches please.
Hope it isn't my eyes going bad?
Fuzzy vision and no adult beverage! LOL

Hello,
You are refering to the coolant vent line, most are probably blocked solid anyway after a few years use, with the real risk of being branded a heretic, I think you can get away with blocking it off completely, but it will take a few days for all the air to bleed out of the cooling system(don't ask me how I know :p ).
The banjo bolts should be in stock at the dealer parts counter.
Hope that helps.

__________________
Nachi11744

This is the water bypass pipe from the head to the block on the front of the engine.

Attached Thumbnails

 

__________________
1981 300SD

I always understood that the purpose of the by pass tube/hose is to allow coolant to flow through the engine while the thermostat is closed. Once the t-stat has opened the coolant flows through the radiator hoses and the radiator.

Bypass is maybe the wrong term, it's to bleed air out of the block etc.
(also holy thread revival record)

__________________
1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD