Hi,

I've got a 96 Chevy Blazer that slowly loses coolant.

Usually takes about 2-3 weeks before the reservoir tank starts to drop below the "add" line.

I've checked for signs of coolant mixing with the oil and all seems clear:

• No milky residue on the oil cap
• Dipstick is amber clear
• Exhaust fumes clear
• No noticeable engine performance issues

Here's what I've checked

1) Hoses all look clean with no visible water marks.

2) Water pump looks very dated and has signs of rust so this could be the issue. I've attached a picture for reference


3) Thermostat housing looks clean with no signs of leakages.

4) Most likely cause of losing coolant is a faulty intake manifold gasket howeverI'm not 100%

There's signs of a leakage directly behind the water pump as show in the picture below


I'm not 100% this is the cause because I would imagine coolant would mix with the oil?

I've also not noticed any signs of poor engine performance and the truck idles just fine.

There's a leak that appears underneath the engine on the driver's side overnight -a small puddle. But I think this might be a small oil leak.

Looking for opinions based on the pictures and what else I should be looking for.

Cheers!

 

Have you tried pressurizing the cooling system with the engine off to see if that will show the leak?

 

The leak can bed anywhere. I've had three slow leaks. 1.) a crack in the plastic part of the radiator near the upper hose that finally got big enough to notice steam, 2,) heater hose at the clamp down in front that finally burst through and overheated the engine (detonation) 3.) leak through the sealant in the LIM crossover in the front of the LIM (seen behind the thermostat, see pic).

You have a pretty good chance of seeing the leak when the radiator water temp is high and engine is running.

Dang. I went out to take a pic of where the LIM leaks and saw my coolant was low. Added some and it started leaking from underneath. Looks like I need a new water pump!