cooling woes

[82eye]

been having cooling issues ever since i built the engine.

for the longest time the car refused to bleed proper. when it finally settled, the heater core and heater core pipe o-rings gave out a couple 100km later. the core developed a small leak, and the o-rings had plasticized and would no longer hold pressure.

replaced the core and o-rings, re-bled the system and all was good. then i took the car on a 700km trip and it threw a low coolant check just as i was getting home. the res was near dry.

oil checks good, no milkshake under the cap, and it was clean and even a touch low in the pan. every single hose is new, no leaks. i'm getting frustrated with it. added coolant and it went through a little over 2 days of short trip city driving. it's not the main car so not many miles.

my best dart toss is maybe the expansion tank or rad developing a leak, but it's a flat guess. called around for a pressure test and decided to try a cheap test kit myself for the price.

anyone have any ideas they can toss in?

[MrBurgundy]

Sometimes there is air trapped and it will eventually make its way up to the tank in exchange for water, so the level will drop.

If you have a leak, just run the car, and it will build pressure naturally. I don't think there's a need for a DIY pressure tester. But same time, it wont hurt.

M20s are waffleswaffleswaffleswaffless sometimes when it comes to bleeding. Also, when you bleed these cars after a heater core leak, make sure the HVAC is switched to heat which actuates the heater valve.

If it's not then water will never make it down into the dash.

So you added after the low coolant trip, then it was triggered again, correct???

It's either remaining air thats trapped, a leak at the core you just did or a leak you haven't found under the good yet...

Run the car at home. If there's a leak, you're gonna see it on the carpet or the driveway. make sure the heater is on too when you do this.

[82eye]

Sometimes there is air trapped and it will eventually make its way up to the tank in exchange for water, so the level will drop.

If you have a leak, just run the car, and it will build pressure naturally. I don't think there's a need for a DIY pressure tester. But same time, it wont hurt.

M20s are waffleswaffleswaffleswaffless sometimes when it comes to bleeding. Also, when you bleed these cars after a heater core leak, make sure the HVAC is switched to heat which actuates the heater valve.

If it's not then water will never make it down into the dash.

it's got great heat, pretty sure the heater core is circulating. there's no warm water on the drivers side footwell, so the valve and heater tubes should be holding.

So you added after the low coolant trip, then it was triggered again, correct???

didn't trigger the second time but was a little low when checked. could've been trapped air from the first low trigger

It's either remaining air thats trapped, a leak at the core you just did or a leak you haven't found under the good yet...

Run the car at home. If there's a leak, you're gonna see it on the carpet or the driveway. make sure the heater is on too when you do this.

have tried. everything remains dry. it seems to only lose coolant when moving.

we're guessing the expansion tank cap may have jammed. it's supposed to let loose at 1.4 bar. in 1997 there was a recall on the caps as the valve in them would seize. the current thought is it's an original cap that is not opening, possibly causing the coolant to escape through the res overflow.

we ran a pressure test with a crappy tester and everything held save for a leak from the tester itself. with a little help for the tester it looks to be holding steady over an hour now.
plan is to order a new cap and expansion tank and see if it holds it. that and the rad are the only things not brand new.

[MrBurgundy]

Sounds about right. Cap seems like the move

[TobyB]

I kinda expect to add a bit more coolant after the system's been open.
It seems like air can hide just about anywheres in there, and only time
lets it fully burp out.

Which is also why I make sure the low coolant light works-
that thingus has saved me many an engine...

t

[82eye]

well, the car blew the return hose off the top of thermostat housing the other day so it's obviously under too much pressure. it will behave around town but you can't do a hard pull or take it on the highway.

i ordered a new cap and reservoir. getting a res from rockauto that was recommended elsewhere. $42 US as opposed to $165. it comes with a cap but i sprang for oe from pelican.

edit: i took the car off the road.

[varg]

Usually caps fail open, not closed. If the cap doesn't do it, which I am not optimistic about, it might be time to see if the cylinders are pressurizing the cooling system. You usually have to have some pretty tired old parts or have to seriously overheat the car to blow stuff up.

Do you have a leakdown or compression test adapter? One cylinder at a time, TDC, in gear and chocked, pressurize the cylinders and see if you get any bubbling or gurgling with the cap off.

[82eye]

Usually caps fail open, not closed. If the cap doesn't do it, which I am not optimistic about, it might be time to see if the cylinders are pressurizing the cooling system. You usually have to have some pretty tired old parts or have to seriously overheat the car to blow stuff up.

Do you have a leakdown or compression test adapter? One cylinder at a time, TDC, in gear and chocked, pressurize the cylinders and see if you get any bubbling or gurgling with the cap off.

i can run a leakdown with the cap off. compression is even 155 across all. car is on a fresh build. there is no oil contamination. car has never hit the red. i'm hoping the head is still good. i dunno how i'd pressurize the cooling system without seeing something transfer to the oil. if anything the oil is down a little.

the coolant definitely blew under hood though. there was the recall on the caps jamming and not allowing pressure out.

my leakdown set is a homebrew i built from the compression tester but has worked on other projects

[TobyB]

Do the cooling system test for combustion gasses.
It's not expensive, and it'll rule out the head gasket
allowing cylinder pressure to
pressurize the water jacket.

t
hoping it's not that.

[82eye]

Do the cooling system test for combustion gasses.
It's not expensive, and it'll rule out the head gasket
allowing cylinder pressure to
pressurize the water jacket.

t
hoping it's not that.

it's $160 plus the fluid here for the tester and it's not available local.

edit: might order a kit but it won't get here til after the parts.

[TobyB]

Oh, jeepsters- less than $50 down here this week for a name- brand one.

t
not sure about after next week...

[82eye]

Oh, jeepsters- less than $50 down here this week for a name- brand one.

t
not sure about after next week...

yeah that really sucks. the fluid alone is as much as the whole kit there including the fluid. i don't think prices will rise for that product in the US, but it is poised to go up here more.

[82eye]

reservoir and cap are in. install and bleeding went good, the car is holding operating temp and doesn't seem to be leaking or losing. will keep an eye for a few days. got a combustion gas tester and will run a test if it throws a curveball.

right now it looks like it was the cap and res causing the issue.

edit: found a combustion gas test kit locally for almost half of the online cost. i dunno how they got so expensive, it's essentially a turkey baster and some liquid lol