coolant leak

[Kenneth Cole]

Hi
I have a 1991 M998 and this has happened twice. This time I was installing a block heater. Got it in and started adding fluid. Got in about 10 quarts and the tanked topped up. So I installed the Rad. cap and after about 15 minutes of running the temp got up to about 160 and it started leaking like crazy down the back of the engine. Not sure where its coming from. So I shut her down and waited about 20 min. I wanted it to dry up some so I could try to see where she was leaking. Well I started it back up and no leak. Like I said this has happed before and also stopped after it cooled off and I drove it for about a week.
So I'm lost and need some advice.

Thanks
Ken

 

[orgnal]

Hi
I have a 1991 M998 and this has happened twice. This time I was installing a block heater. Got it in and started adding fluid. Got in about 10 quarts and the tanked topped up. So I installed the Rad. cap and after about 15 minutes of running the temp got up to about 160 and it started leaking like crazy down the back of the engine. Not sure where its coming from. So I shut her down and waited about 20 min. I wanted it to dry up some so I could try to see where she was leaking. Well I started it back up and no leak. Like I said this has happed before and also stopped after it cooled off and I drove it for about a week.
So I'm lost and need some advice.

Thanks
Ken

Some times it is the small things that can get you. How old is the radiator cap? If it is not holding the pressure down, the coolant might be spewing from the overflow tube on the coolant expansion tank / reservoir. Change to a new radiator cap and see if the problem is solved.

McReddy

 

[dskupi01]

I concur with the previous comment. Follow the overflow tube from the cap. Was this where it was leaking? System was likely slightly overfilled, expanded, then leaking down overflow tube. I've found the coolant in the system expands significantly. The syptoms you have are consistent with this. Put a flashlight on the tank at full temp. Filled to the brim?

 

[Kenneth Cole]

Hi
The leak isn't coming from the overflow tube. I pulled the dog house forward and could see fluid coming from the front of the engine and running down the back of the engine. My thought was the water pump but why would it only happen a couple of times?
Ken

 

[orgnal]

Hi
The leak isn't coming from the overflow tube. I pulled the dog house forward and could see fluid coming from the front of the engine and running down the back of the engine. My thought was the water pump but why would it only happen a couple of times?
Ken

Your best bet is to identify where the source of the leak is ...

McReddy

 

[Kenneth Cole]

McReddy

Your right, I will try to do that the next time it leaks. Thanks all for your help.\
Ken

 

[juanprado]

On stubborn leaks that are hard to find, One way is to use a dye in the coolant and then a blacklight. Napa sells the dye bottles and light if needed.

 

[Swisscheese]

I've run into a few problems with the crossover up front, usually near the thermostat. Sometimes it will corrode and leak from there to the top of the engine, and out the back. Maybe worth checking out, they usually start as pinhole leaks

 

[NormB]

I've run into a few problems with the crossover up front, usually near the thermostat. Sometimes it will corrode and leak from there to the top of the engine, and out the back. Maybe worth checking out, they usually start as pinhole leaks

I changed every hose in my cooling system EXCEPT the one from the crossover to the water pump. 3/4“ ID about 5“ long, IIRC. Didn‘t look too bad and it was after working on the cooling system most of a Saturday and what the heck, I‘ll get around to it.

Shortly after changing engine oil I started seeing „oil“ under the engine. VERY slow drip, one or two a week or so. What is that, a „class 3 drip“? No motor pool sergeant around, I investigated further after seeing it on the harmonic balancer.

It FELT oily anyway, and I could see it coming from just below the oil filler pipe, side of water pump appearing a little shiny. Maybe I spilled some - matter of fact I KNOW I did - refilling the oil. Wiped it down and drove for several more short trips.

More drips.

Took a steam cleaner and some degreaser to the front of the engine, drove around some. Couple weeks later, drip was still there. This time I could see it on the large sheet of cardboard I keep under the truck in the garage and... it was a little yellowish looking. So I took a piece of paper towel to the crossover/thermostat block and other places (folded up you can touch it to different spots and look at the towel for oil, coolant, ATF or whatever) and yeah, it was the old hose. So I went to NAPA (Make and model of your car, please?) and bought a foot of hose.

Months later, there‘s this drip... again.

Coming from the TOP of the hose. NOT the threaded adapter piece. Torqued the hose up a bit more. Time will tell if I need to disassemble this, reseal and/or replace some or ALL components, wrap fitting with some teflon tape, double clamp it or use an even WIDER hoseclamp or what else I don‘t know.