BCM Community

My 40 year old MC5 seems to have a coolant problem which requires the help of you MCI experts.

It seems that as time goes by I need to have to add more and more coolant mixture to the cooling system.  I have no problems running down the road..it doesn't appear to overheat and I find no evidence of leaking. Needless to say, I'm puzzled. I've pulled and disposed of the shutterstats which were working OK...but another BusNut needed them more than me. The engine has never overheated.

It usually took a couple of gallons of 50/50 mix to top it up for the last year or so but  this spring it took over 6 gallons. Now, in all honesty I didn't open the petcock on the thermostat housing (8V-71) when I filled it and didn't have a problem on the 450 mile trip home.

But these things have a way of preying on your mind. I cannot see and any signs of leaks at hoses (had  them all replaced 2 years ago when I pulled the engine) and no leaks at the radiators. Any ideas?

Any thoughts would be appreciated......

NCbob

Forgot to aks this question....it's been sooo many years since I went to DD School....if I left the radiator cap loose would it temporarily solve my problems of losing coolant?

Also I have the GM (DD) coolant filter on the engine...I might think about removing the element and solving the problem...but I think that might add to an overheating situation...but really it's a bypass filter......

Opinions?

Bob

Bob I went through the same thing with my 5C. The coolant was going somehere, but where? Coolent Vampire bats, that sucked it out as I went down the road? It is not alcohol anymore so the drunks were not drinking it when I was not looking. I watched for years and could find no culprit, no spills, no stains, no trace evidence anywhere.
Aided by non other than the Exhaulted Grand Pooh Bah, Jerry Jenkinson. (That is not an insult, it means holder of many titles) I managed to fix the problem.It was a two part fix. First the over pressure relief on the expansion tank was past retirement age, it no longer functioned. Which was not a problem because the fill cap washer, was also beyond retirement age. It was old and brittle and did not seal.
I was now faced with a delima, spending a large amount of money on hard to find expensive parts!! spending money always ruins my attitude. Or finding another approach.
Here is how I did it. Now remember I am not a pro, just cheap. First I made a trip to a radiator shop and purchased a fill neck for a radiator, the part the cap screws on.  Next I removed the fill cap assembly from the bus, and removed the cap. I then cleaned up the base so the fil neck would fit. The next part was hard, not trusting my soldering skills I actually paid (shudder) the radiator shop in Arcadia to solder the fill neck to the base!! I also purchased a new 7 lb radiator cap.
The bottom of the fill assemby on the bus has become uneven over the years and needs to be leveled. It is brass so easy to do. Find a nice flat piece of steel and some sandpaper, grit is determined by how much material you have to remove. Simply move the part over the sandpaper on the steel until you have flattened the bottom!  IIRC I also had to make a gasket for the base.
I removed the original pressure relief assembly and installed a pipe plug into the tank. Reinstalled the base, added the radiator cap and no more problem!!!!
I will poke around and see if I can find pictures.  HTH Jim

Quick archive search and there it is!!!

     

Bob - As said I would start with a new cap too - Are you saying it's loosing coolant while sitting there? That would be quite a conundrum - If your loosing it while operating it, try this (I know you said new hoses but clamps have a way of working themselves loose) - dust some chalk at each of your hose connections and take it out for a hard run - If you have any leaks there they should be quite evident - HTH

Check the main heater core (in cargo bay), main water valve (in cargo bay) and front heater core and water valve. Check the engine oil for contamination too. Good luck.

Please don't laugh now.  I have found some mysterious water leaks with "red food dye".  A friend with  a Fiat was perplexed that his car was empty of coolant when he got home but was still full when he got to work.  So happened he lived way up in the mountains.  I suggested that he load up his cooling system with dye on Friday after work and I would visit on Saturday morning.  It is a nice drive up into the Mt's. on the week end.  His number two plug was a really nice shade of pink.  The rest seemed normal.  I suggested he complain; to a mech and tell him the "pink plug story".  Head gasket!

Another was a hole in the center of the rad that evaporated the coolant as fast as it came out.  Center of the rad turned RED after a week.  Fixed with JB Weld and was still holding 3 years later.

This doesn't work if there isn't any actual coolant flow in the leak.

Red dye....who wood'a thunk it,

John

If you're loosing it while the bus is sitting, especially if it's during winter, then it's probably due to cold coolant leaks at the hose clamps. As the pipe cools, it shrinks more than the clamps do, and then you get a tiny leak. Even with the so called constant tension clamps. If you have silicone hoses, it's even worse, because they never stick to the pipes, and readily leak with the slightest loss of tension.

Since buying my bus, I've had to buy more antifreeze than I ever had in all my life, and previous life combined!
Every November, I go out and start tightening all my hose clamps in my bus. If I don't, I'll lose up to 6 gallons just sitting through the winter dripping.

To beat the silicone hose weep problem you need to either paint the fitting or smear it with JB weld before tightening.  You can also coat it with JB and let it harden before you assemble the connection.  The rust surface becomes a channel for leaking.

HTH

John

Thank you for all the pointers, guys. I normally don't check the coolant at the end of a run (shame on me) but check it before my periodic start-ups to air up the bus and certainley before I take a local run.

I have a nick in the flange in the filler neck and the gasket and the brass deal on the cap seem OK.

It'll take this old man a few day to check things out but with a storm approaching south FL one of my girls might just need our 12.5 KW Kohler to keep their lives a bit more comfortable.

Promise I'll report back.

NCbob