2000 S70 Coolant Slowly Decreasing

[tjmartin317]

2000 S70, non turbo, piece of junk with a million other problems, but the topic of tonight's cry for help is coolant.

I recently did the coolant temp sensor and thermostat replacement to fix my wonky gauges, and it was a massive success! I originally did the job back in early January, maybe even December. But because I'm a dummy, I decided to try reusing the rusty hose clamp holding the upper hose to the thermostat housing rather than using one of the dozens of hose clamps we had in the shop.

Surprise surprise, it didn't seal very well, and the loss off coolant got so bad that my coolant level light came on (thankfully that happened at the gas station). Now I've been fighting with a coolant reservoir that slowly gets lower and lower. Been topping it off ever since, something I didn't have to do before I fiddled with the system.

Many suggest air, and that's likely what it is. There are no drips on the ground (that I've seen) and no white smoke from the tailpipe... but it's been, like, a month... and I feel like every couple trips it's lower than it was before... So if either of those previous issues are occuring, I'm a bit concerned about the 800-ish mile round trip to Michigan I plan on taking... tomorrow.

Figured I'd bring the beater to David Tracy's farewell from Troy instead of my daily (sidenote: if anyone on this forum is going to be there let me know, I'll be wearing a red Ohio beanie). And, ironically, the Volvo has a far better heating system and snow tires, and most recently had an oil change. It's the ideal tool for the job... miraculously...

Now, I did a little test. I drove the car to work on Monday and then to an event on Wednesday. About 30 or 40 miles round trip. Dead on the max line Monday morning. Checked the reservoir tonight and I was maybe half an inch lower than before. Not a huge drop, but considering the first trip to my overnight hotel is 200 miles, it's a pretty significant loss of coolant... if I'm losing it... which may or may not be true. I know enough about cars to know how to fix things, but not enough to know how they work.

Either way, I'd like not to have to wait an hour or two in the middle of the night for the engine to cool down enough so I can open the pressurized reservoir cap to top off my coolant. I'm considering using my hour lunch break tomorrow to just shoot up a highway in one direction for half an hour, and then the other direction for the other half hour. Then letting it cool, checking again after work, and going from there... it's a lot of extra driving on a day I'll be road tripping, and a good bit of gas, but the ol' 5 cyl is economical enough.

Maybe you're going to look at me like I'm an overthinking maroon that just wasted a perfectly good slot on this esteemed forum... but either way, I appreciate any and all advice, counsel, and guidance.

[volvolugnut]

Suggestions:
Check that all the coolant hose clamps are good and tight.
Look all around any coolant connections you changed for any sign of dried coolant.
Check your oil for any sign of milky oil.
Burp the top coolant hose many times to assure all of the air is out of the hoses and the coolant system is completely filled.
But you knew all that.
volvolugnut

[tjmartin317]

Suggestions:
Burp the top coolant hose many times to assure all of the air is out of the hoses and the coolant system is completely filled.

You assumed incorrectly about me knowing all that. What's the best way to burb that hose? Just squeezing it a bunch? While the car is running or off?

No sign of oil in coolant or coolant in oil last I checked, will double check.

[WhatAmIDoing]

My S70 was plagued by the same issue, but I was only adding a quart of coolant every 4 months. I replaced all the hoses with silicone and expensive stainless hose clamps, new heater core, new res, new cap, basically everything except the rad. Unfortunately, I was still loosing coolant and ultimately suspected a bad head gasket. Fortunately, you don't have turbo coolant lines to deal with.

Remember, coolant levels vary widely with temperature. The cold weather makes this variance appear very extreme.

Basically do as volvolugnut suggested. If all your hoses are original, they are over 20 years old and could easily be seeping past the hose clamps. Check that your clamps are tight, but resist the urge to over tighten them or those old hoses will leak more.

With the system cool, squeeze the upper rad hose until it starts to feel firm. This will help bleed a lot of air out of the system. I've also learned driving up a steep (and I mean STEEP) hill does an excellent job at burping the cooling system. Grab a flashlight and check around the thermostat housing. When I changed my thermostat, I didn't clean up the matting surfaces and it leaked really bad. But since the leak ran back behind the manifold, it went undetected for months.

Have you removed the kick panel under the dash and checked the heater core? They are known to fail after 15 years. Is the carpet wet under your feet?

NAPA sells UV leak detection dye for less than $8. Grab a cheap UV flashlight and any leaks will stand out in a dark environment. The coolant residue will also dry neon orange.

[scot850]

Your carpets may not feel wet on the top if the heater matrix is leaking as they are rubber backed and the coolant will drain under the carpet. Pull the carpet back on the drivers' side front foot well and see if it is damp underneath.

Another telltale for heater matrix/core leak is fogging on the windshield and a slightly sweet smell in the car. Try running a finger across the windshield just above the windshield air vents and see if the windshield is greasy.

How is your engine oil? The pancake oil cooler on the back of the oil pan can fail internally.

Check your transmission oil for milky look. The radiator is used for cooling the trans fluid and they can fail internally allowing the fluid to mix.

Simple check, remove the coolant cap on the header tank and look for residue of coolant under the cap and around the header tank. The radiator cap can fail and aftermarket ones can open too early and leak about 1/2" at a time as the engine cools.

Last place to check is the water pump. When cold or when cooling after a run the bearing seal can leak fluid.

Neil.

[tjmartin317]

This will help bleed a lot of air out of the system. I've also learned driving up a steep (and I mean STEEP) hill does an excellent job at burping the cooling system.

... this could be the issue... I drive up a steep hill every day... because I live on one... maybe that's why it seems to always be low once I'm home?

No wet carpets cause I've got rubber mats... and no wet mats either. I'll squeeze the hose, check my oil, and hopefully sleep peacefully once both of those present good results...

And to address Neil's advice, I've got a stick, so no trans fluid. And the cabin is dry/unsweet. All fog is just condensation from the area I live in that quickly goes away with the heater.

[volvolugnut]

A heater core leak will run down the fire wall and get UNDER the carpet and the thick carpet pad. You will not be able to check this by feeling the top of the carpet. You have to lift up the carpet and pad. You will then also be able to see if you have a windshield or sun roof leak to under the carpet.
What Am I Doing is right about burping the hose. Do this with the cap off and keep doing it until the level stops dropping in the overflow tank.
volvolugnut

[tjmartin317]

What Am I Doing is right about burping the hose. Do this with the cap off and keep doing it until the level stops dropping in the overflow tank.
volvolugnut

Checked all oils and stuff, and burped the hose until is wouldn't drop. Then I lifted the carpet... holy moly it's damp... borderline wet... just lifting the carpet revealed a puddle that stretched almost all the way to the seat, and I don't know how recent it is... Would running out of coolant when my coolant light came on have caused this?

Either way, there's my leak... and I'm gonna guess that isn't a quick job to do... and is enough to prevent this car from making the trip...

[tjmartin317]

Alright, after some digging and talking to my co-pilot for the trip, it seems like the trip is still doable, just won't have heat... Going to test this theory by not using any heat tomorrow to ensure that reservoir stays at the max line like I know it should. Once that's proven to be right, we may either go on our journey, or we may try and fix the heater core right then and there. Not exactly a tough job, but a job nonetheless.

Here's the damage:

IMG_5988.JPG (22.71 KiB) Viewed 876 times

Yeah, a new carpet would be needed. Judging by how dirty it is, I'd bet this has been an issue for *way* longer than I've owned this car.

Oh, and in case I haven't said it, ***thank you*** for helping me find this mystery leak.

[MoVolvos]

"just won't have heat... Going to test this theory by not using any heat tomorrow to ensure that reservoir stays at the max line like I know it should.

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It's probably close to 10 years since I did the heater core replacement on the 98 S70 T5. I believe the coolant is always circulating through the core so the leak will continue. The controls just moves the damper to direct heat to the various vents. Someone confirm this please.

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