Hi,

I have a 1986 190d 2.5 N/A

I am losing coolant and I think I am losing it from the diesel pre heater, thermostat.

I am losing about a pint every 500 miles. I am having a hard time even finding the leak, but every other section less the left side of the engine bone dry. There is no wetness or moisture on either driver or passenger side footwell so I suspect it is not the heater core.

I did disconnect the pre heater awhile back, but I think I am leaking both diesel fuel and coolant from it anyway.

I would like to remove it and rebuild it. I can't seem to find a rebuild kit.

Does anyone know where I can find one?

Thanks.

Sounds like you need one of those coolant system pressurizing tester to pressurize your system.

Well, the harbor freight one is expensive. Have not done it lately but it used to be on the harbor freight site you could view a PDF of the instructions and with that you could find out if there is an adapter for your Mercedes.

Do a google image search for: Coolant pressure tester harbor freight

The below video the guy has a similar issue, but it does not show him using the kit, but he said he found his leak.

https://www.youtube.com/watch?v=8VJbaXjQL6c

If a tiny amount of coolant is getting into the cylinders by way of a head gasket leak you won't know it unless there is enough to alter the exhaust smell.

I have also seen tiny pin hole coolant leaks with the same symptoms.

The telltale sign with the old green coolant is a white crusty area develops around or near the leak area, but you don't see any liquid especially if the engine is hot. The last one I saw was a leak in the engine block were there must have been some sort of porosity in the block itself. But leaks like that are more typical on hose connections and things like the thermostat housing.

One of the areas to check is the back of the engine between the engine and the fire wall and check the core/freeze plugs.

__________________
84 300D, 82 Volvo 244Gl Diesel

Thank you! I will check those areas.

https://www.pelicanparts.com/byv-w201-190d-2-5-1986-2-5l/b-genuine-mercedes/c-miscellaneous-hardware_c-wipers-washers_c-windshield-washer-reservoir-parts


This part might be inside your windshield washer fluid reservoir. On my car, I was losing a smidgen of antifreeze with no trace of where it was going. I was able to replace o-rings and leak went away. Antifreeze simply mixing with washer fluid from the temperature controlled valve.

Thanks. I will check for that part inside the reservoir.

Here is a thread that may help, from a good friend who died in 2009.

OM601, Diesel Fuel Heater.....

and another good link
https://www.youtube.com/watch?v=KRMVGd8Zbmk

.

__________________
ASE Master Mechanic
asemastermechanic@juno.com

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
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

Just do yourself a favor, and delete/bypass the entire thing from the system.

__________________

All Diesel Fleet
1985 R107 300SLD TURBODIESEL
2005 E320 CDI (daily)

LOTS of parts for sale!


EGR block kit
http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html

1985 CA emissions 617 owners- You Need This!
Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst.

Sanden Instalation Guide (post 11):
http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html