Coolant loss and overheating.

perhss70 · Post by **perhss70** » 17 Jul 2024, 12:51

97 s70 2.0T

I am losing coolant for a while. It is random, once the whole expansion tank got emptied after a trip(no light came on the dash while traveling, I parked it and after 2h it was empty).
90% of the time I can't see leaks, last week it overheated while traveling. I went to the mechanic and he had it running for hours, no leaks. Today I changed the radiator since I saw the edges having red color (coolant). It overheated again on the way home. Any tips on how to proceed? Both times it overheated the coolant was boiling.

Oro · Post by **Oro** » 17 Jul 2024, 14:24

I would suspect a failing thermostat based on the initial symptoms. Thermostats typically fail open and do not cause overheating (rather, the opposite). You can test this theory with a cheap IR temp gun if you have one (or want an excuse to buy one - they are quite cheap these days, and fun to play with).

I am assuming the mechanic was competent enough to have spotted a head gasket leak, were that the issue. It’s another possibility. The HG leak also causes the reservoir to empty, as the added gas volume blows the coolant out of the system.

Post by **scot850** » 17 Jul 2024, 16:16

It can depend on the type of thermostat fitted. Several aftermarket ones do not have the little jiggle bypass so if they stick shut they will cause an overheat quickly. I agree with Oro, I would suggest starting with the thermostat.

If that does not fix it, even after fitting a new radiator, I would also check the fan is coming on. If the car is relatively ok on a highway, but overheats in traffic, chances are the fan is not being triggered.

Neil.

perhss70 · Post by **perhss70** » 19 Jul 2024, 07:23

I did a hg leak test. Even with empty tank when I turned the car on the coolant would rise very fast and spill out. The car is at the mechanic atm and I will change the motor with one I had with 100.000ish km

Post by **BlackBart** » 19 Jul 2024, 09:16

There’s a solenoid on the upper rear side of the radiator that controls the fan coming on. My ‘94 overheated long ago and that was the issue.

Post by **MoVolvos** » 19 Jul 2024, 15:35

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The 98 S70 T5 in 2012 had a problem with the needle going to the red and fluid out of the cap. It would do this at times when idling too long. I think it was doing the PCV that I remove the thermostat housing and found no thermostat

. Put one in and the problem went away. Whether stuck open or closed it will create a problem but it may not be yours.
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Borrow the tester at Advance or other big box and purchased the fluid to check for HC. You can also just get the kit if you like. I borrowed mine from Advance and they charge you the regular purchase price. I forgot to return it and since it was new never used just decided to keep it. The expansion tank fill hole maybe too large so may have to improvise.
.

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Post by **scot850** » 19 Jul 2024, 15:43

The OP says he did a headgasket (hg) test, but not the result of that. I'm going to assume from his following info the gasket had failed and so assuming in this case it is cheaper to swap a whole lower mileage engine.

Neil.

Post by **MoVolvos** » 19 Jul 2024, 19:06

scot850 wrote: ↑19 Jul 2024, 15:43 The OP says he did a headgasket (hg) test, but not the result of that. I'm going to assume from his following info the gasket had failed and so assuming in this case it is cheaper to swap a whole lower mileage engine.

Neil.

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I missed it. Hope the test was done correctly per video. At my suggestion my neighbor purchased one but he kept drawing coolant into it so I went over and redid the test for him.
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perhss70 · Post by **perhss70** » 21 Jul 2024, 01:51

MoVolvos wrote: ↑19 Jul 2024, 19:06
scot850 wrote: ↑19 Jul 2024, 15:43 The OP says he did a headgasket (hg) test, but not the result of that. I'm going to assume from his following info the gasket had failed and so assuming in this case it is cheaper to swap a whole lower mileage engine.

Neil.
.
I missed it. Hope the test was done correctly per video. At my suggestion my neighbor purchased one but he kept drawing coolant into it so I went over and redid the test for him.
.

Yeah sorry forgot to clarify. The hg test did show that it failed. The engine has around 350.000km so it was not that unexpected. Imo just changing the hg wasn't worth it so motor swap it is.

Post by **scot850** » 22 Jul 2024, 09:34

That makes a lot of sense. At that mileage I can see that makes sense. Thanks for clarifying!

Good Luck!

Neil.