Coolant usage?

[RTegarini]

Originally Posted by tmw188

New Radiator cap...

Hello... I was hoping you could post the radiator cap brand and model number. I’m losing coolant too and would like to start with the cap replacement. I did a search at a Workhorse parts site and come up with different part numbers, running from $15 to $50.

Thank you - RT

[olskool4x4]

ACDelco RC81 GM Original Equipment or RC27

[tmw188]

Originally Posted by RTegarini

Hello... I was hoping you could post the radiator cap brand and model number. I’m losing coolant too and would like to start with the cap replacement. I did a search at a Workhorse parts site and come up with different part numbers, running from $15 to $50.

Thank you - RT

I bought it at Napa nothing special take your old one with you.

[Jeff H]

Very interesting reading all these posts. My coach 2006 with 128K has had this "problem" since new. I have done all of the above, changed all hoses, water pump and radiator cap. My wife, a former service advisor for many brands, can smell coolant from a block away. Every trip, when I check the oil, she asks if I checked the coolant. We owned a shop for 37 years and between myself, GM, former GM techs we had working for us, No one has found where the leak is.

[akpd]

Originally Posted by Jeff H

Very interesting reading all these posts. My coach 2006 with 128K has had this "problem" since new. I have done all of the above, changed all hoses, water pump and radiator cap. My wife, a former service advisor for many brands, can smell coolant from a block away. Every trip, when I check the oil, she asks if I checked the coolant. We owned a shop for 37 years and between myself, GM, former GM techs we had working for us, No one has found where the leak is.

Intake manifold gaskets?

[olskool4x4]

New Rad-Cap still losing Coolant?

(One Possibility)

Sometimes the Radiator Neck (Slide Rails) pull up a little over time. This prevents the cap from being pulled down tight and the rubber seal lets coolant pass when it builds pressure.

How to Test: After the Cap is on, push down on the cap to see if it move’s down. If its solid your good. If it moves down the rubber seal is not as tight as it could be, tap down on the slide rail “a little”. This pulls the cap down tighter preventing coolant from passing under the rubber seal before pressure lifts the spring.

[akpd]

Originally Posted by olskool4x4

New Rad-Cap still losing Coolant?

(One Possibility)

Sometimes the Radiator Neck (Slide Rails) pull up a little over time. This prevents the cap from being pulled down tight and the rubber seal lets coolant pass when it builds pressure.

How to Test: After the Cap is on, push down on the cap to see if it move’s down. If its solid your good. If it moves down the rubber seal is not as tight as it could be, tap down on the slide rail “a little”. This pulls the cap down tighter preventing coolant from passing under the rubber seal before pressure lifts the spring.

Well put, but if this was the issue wouldn't the overflow tank level increase from the seal leaking?

[olskool4x4]

Yes (Maybe), I seen mine dripping from the cap. I tap down the rails and the drip stopped.

[iRV4FUN]

I know this issue has been talked about before on irv2. I did the radiator cap, the pressure test, and had numerous qualified mechanics look at and couldn’t diagnose my problem. My coolant temp sender leaked only when the engine was cold. It was by chance that after the OEM header was replaced with a Bank’s that the fluid took a different path and I could see it. I noticed a lot of rust on parts near the coolant temp sender. I strongly suggest some of you to look at the coolant temp sender on the passenger side between the two rear spark plugs. This is a common leak for the 8.1L. And the good news is it’s an easy fix.

[tmw188]

Originally Posted by akpd

Well put, but if this was the issue wouldn't the overflow tank level increase from the seal leaking?

My tank definitely rises as it gets up to temp. I check for loss after it has cooled like in the morning. I will look at the sending unit again.

[iRV4FUN]

I’m pretty sure there’s a WHCC technical bulletin and numerous posts on checking radiator fluid level and the false readings from the overflow tank. After the engine has cooled to a safe temperature I’ll remove my radiator cap to check my fluid level. The tank is a quick visual but certainly not a reliable indicator that something is wrong.

[tmw188]

Originally Posted by iRV4FUN

I’m pretty sure there’s a WHCC technical bulletin and numerous posts on checking radiator fluid level and the false readings from the overflow tank. After the engine has cooled to a safe temperature I’ll remove my radiator cap to check my fluid level. The tank is a quick visual but certainly not a reliable indicator that something is wrong.

It’s going somewhere if you always have to top it off to the cold mark when it’s cold. If I don’t it will eventually be empty. It’s not coming out the tanks overflow.

[iRV4FUN]

Originally Posted by tmw188

It’s going somewhere if you always have to top it off to the cold mark when it’s cold. If I don’t it will eventually be empty. It’s not coming out the tanks overflow.

I absolutely believe that you have a coolant issue and I know what that feels like. Sorry I hijacked your thread. I learned from the iRV2 WHCC legends that used to post here that the overflow tank is NOT ALWAYS a good indicator of the actual radiator fluid level. Also remember a Technical Bulletin on this subject. Also as I took note of this potential discrepancy I noticed this to be the case.

[tmw188]

If it wasn’t going somewhere the overflow tank once pressure cools down would return to the same level. Now if that cold level was too much it would expand and go out the overflow, however no signs of that.