cooling system pressure test - PeachParts Mercedes-Benz Forum

Phillytwotank · #1 07-05-2016, 08:22 AM

y'all, i need a little help here.

can anyone share with me a good way to get set up for pressure testing the cooling system on a om602 turbodiesel please?

loosing coolant at an alarming rate. Don't see any obvious signs of where the coolant is going.

Thanks

dieselbenz1 · #2 07-05-2016, 10:05 AM

I've placed a tee in the long line between the engine and reserve tank and pumped it up which worked well.

Have you checked your engine oil and transmission fluid for contamination? Are there bubbles in your cooling system reserve tank?

How much is an alarming amount of fluid?

Phillytwotank · #3 07-05-2016, 10:34 AM

no signs of water in oil in the engine or the transmission. its loosing about a gallon per 150 miles.

no bubbles in the reserve tank. no withe smoke in the exhaust. no white residue from coolant spray that i can find anywhere.

i rigged up a pressure test setup from some parts i had around the plant. tee'd it into the small hose running from the top of the engine over to the tank. Pumped it up to 8psi and it slowly leaked down. i could hear a small hissing sound coming from like the oil filter corner side.

I'll have to wait until later to do it again and really narrow in on where its coming from.

dieselbenz1 · #4 07-05-2016, 01:57 PM

There is an o ring seal on a steel water line which mounts to the head in that general area. Maybe that but odd you can't see it drip? Did you remove the belly pan yet?

Demothen · #5 07-05-2016, 02:01 PM

You might get a UV flashlight and see if it makes your coolant glow. That will help you find leaks. If your coolant doesn't glow under UV, there are some dyes you can add that will make them glow - just make sure to get the type for water, not AC systems or oil systems.

Jeremy5848 · #6 07-06-2016, 12:53 AM

This won't find your leak but . . . I put a small 15 psi pressure gauge in a handy coolant hose of my '95 E300D. It allows me to check the coolant pressure after driving the car and watch as the car gradually cools down. Typical pressure on a cool day w/o air conditioning, about 9 psi. On a warm day when the a/c has been used, about 12 psi. It can take several hours at home in the garage for the engine to cool and bring the pressure down to zero. Should the cooling system spring a leak, I'll be able to tell by the changes in the displayed pressure.

Jeremy

BillGrissom · #7 07-06-2016, 09:29 AM

Harbor Freight sells a radiator pressure kit, I recall, that might be adapted. You might suspect your heater core. If it leaks, the coolant will flow out the climate drain, which drips onto the transmission. The factory used a foam tube that disintegrates, letting condensate drain onto the floor (posts w/ fix). Where you live, you will get much condensate from the AC, but that should be clear vs your coolant color. Not hard to bypass the heater core by re-routing one hose. That would tell you for sure. In the winter, a heater core leak will fog the windshield, and give a coolant smell.

GregMN · #8 07-06-2016, 09:58 AM

Quote:

Originally Posted by Phillytwotank

no signs of water in oil in the engine or the transmission. its loosing about a gallon per 150 miles.

If you are loosing that much and you don't see it leaking out of the cooling system, it is going out the tail pipe.

vstech · #9 07-07-2016, 12:25 AM

Quote:

Originally Posted by Phillytwotank

y'all, i need a little help here.

can anyone share with me a good way to get set up for pressure testing the cooling system on a om602 turbodiesel please?

loosing coolant at an alarming rate. Don't see any obvious signs of where the coolant is going.

Thanks

Come borrow my radiator pump up kit...

My money is on the aux water pump...

jay_bob · #10 07-07-2016, 12:34 AM

Mine is on the heater hose connection to the block. There is an o-ring on that joint that gets old and fails. And it's in the area where you heard the noises.

Phillytwotank · #11 07-08-2016, 10:19 AM

Thanks everybody for the input!

I've been cautiously optimistic for the past couple of days but today i'm happy to report the leak has been found and fixed.

I could hear a little his with the system under pressure. later on that day when things quietened down i was able to stick my head in there and find it. Long story short, it was just a loose hose clamp on on of the heater hoses back behind the oil filter housing.

I feared that it was going to be worse but i was relived to find that it was just that. Amazing to me how much it was loosing through just that little hole.

And as a bonus i just did a coolant change.

Thanks everybody