Losing Coolant

thraxxx · October 23, 2008

I have a 1989 GMC Sierra with a 350 from a 1987 Sierra powering it. I am currently losing coolant and I have no idea where its going. I checked the oil and there is no signs of white residue from a potential head gasket leak. The exhaust has no distinctive smell of burning coolant. I am at a loss as to where it could be going. I thought it could be leaking out the rad so I filled the rad and put a piece of cardboard under the truck to see if it was leaking out the bottom, but it was dry the following day. No signs of coolant stain on it. I figured it probably evaporated from the cardboard so I poored a very small amount of collant on the cardboard to see if it would stain and it most certainly does. I replaced the rad cap as a buddy of mine told me it could be evaporating through the rad cap.

I am completely puzzled by this. Are there any other tests I can perform to find where my coolant is going?

2000DV4.8 · October 23, 2008

Have you checked the water pump area? That's where mine's leaking from. Also, how quickly is it leaking?

I believe on the older motors a leaking intake manifold gasket could also cause coolant loss.

Draenor · October 23, 2008

I could be leaking slowly enough on the engine, to where the coolant is being burnt off, leaving no "evidence" behind. As Dan stated, look closely around the pump. If not there, its probably the intake manifold gasket.

Draenor · October 23, 2008

BTW, you can get a pressure tester and test the cooling system. The local parts stroe may do a free lend a tool.

thraxxx · October 23, 2008

If you are talking about the rad housing that bolts where the thermostat sits, then yeah I checked that and its dry there. If its in the intake manifold gasket where could it be going? Would doing a collant preasure test tell me of a leak in the system?

That is the one thing I haven't done...mainly because I don't have that tool handy.

Draenor · October 23, 2008

If you are talking about the rad housing that bolts where the thermostat sits, then yeah I checked that and its dry there. If its in the intake manifold gasket where could it be going? Would doing a collant preasure test tell me of a leak in the system?

That is the one thing I haven't done...mainly because I don't have that tool handy.

No not at the thermostat. At the pump, where your fan is bolted to. There is small weep hole on it. It is there to let you know if coolant is leaking out of it, the pump is failing.

thraxxx · October 23, 2008

oh..never checked that. Ok I will check that out and go from there.

Mike G · October 24, 2008

Sometimes a slow leak out of the freeze plugs will keep you looking for a while...

txab · October 24, 2008

How much are you losing over what period of time? Look into the heater core also. I had one that was losing small amounts of coolant. Finally tracked it down to the heater core when it got cold enough to need heat..... smell of warm ethylene glycol.....

Z45 · October 24, 2008

Find it once and for all? Go to the GM dealer, tell them you got this annoying leak you can't find and if they will put tracer dye in the system and pin point the leak. The dye will show up under a black light even though you cannot see the coolant leaking.