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Cooling system leak / pressure test question #4692257
03/12/18 09:01 AM
03/12/18 09:01 AM
Joined: Jun 2003
Posts: 632
McGregor TX
mrdctaylor Offline OP
mrdctaylor  Offline OP
Joined: Jun 2003
Posts: 632
McGregor TX
Hey guys,

I've had a coolant leak in my son's 2003 Santa Fe for months. The reservoir goes from the full line down to below the low line in around a month. There was never any evidence of it being in the oil and it wasn't a fast enough leak to make it to the ground and pool up. A couple of months ago, I took it in and my mechanic did a pressure test and couldn't find anything. He said it held pressure over night. He replaced one hose clamp where there were a few drops of coolant, but other than that he couldn't find anything. Fast forward to a couple of weeks ago. I took it back in because it was still losing coolant regularly. This time he drove it around and got it good and hot before putting it on the lift, since a pressure test hadn't shown anything previously. This time he could see some coolant leaking from the water pump. Fortunately for me, this was still under warranty because he'd had to replace it this past summer when the original water pump went belly up. I guess we just got a bad pump since it had pretty much had a coolant leak since then--we just didn't realize it immediately. It looks like that finally solved the leak.

So my question is this: Why would this leak not show up under a pressure test? Why would it only start leaking when hot? I mean, it sort of makes sense, but I just like to understand exactly what's going on with my vehicles so I'll know what my mechanic is talking about.

Thanks in advance!


02 Tacoma 3.4L, 219K, Magnatec 10W30
02 Trailblazer 4.2L, 179K, Edge HM 10W40
12 Highlander 3.5L, 99K, Napa Syn 0W20
17 Escape 2.0L, 31K, Hav ProDS 5W30
Re: Cooling system leak / pressure test question [Re: mrdctaylor] #4692271
03/12/18 09:13 AM
03/12/18 09:13 AM
Joined: Oct 2009
Posts: 386
California
Billbert Offline
Billbert  Offline
Joined: Oct 2009
Posts: 386
California
Nearly everything expands when heated, different materials expand at different rates and clearances change. Could have been a tolerance stack up problem.


If you think you can, or if you think you can't, You are probably right.

Auto Instructor / ASE Master Tech
Re: Cooling system leak / pressure test question [Re: Billbert] #4692273
03/12/18 09:15 AM
03/12/18 09:15 AM
Joined: Jun 2003
Posts: 632
McGregor TX
mrdctaylor Offline OP
mrdctaylor  Offline OP
Joined: Jun 2003
Posts: 632
McGregor TX
Originally Posted By: Billbert
Nearly everything expands when heated, different materials expand at different rates and clearances change. Could have been a tolerance stack up problem.


Right. That's my thinking. But by the same token, a pressure test seems to be THE test for cooling systems. Maybe that's a misunderstanding on my part. Unfortunately, at least in some cases it gives a false reassurance that there is no issue. :-/


02 Tacoma 3.4L, 219K, Magnatec 10W30
02 Trailblazer 4.2L, 179K, Edge HM 10W40
12 Highlander 3.5L, 99K, Napa Syn 0W20
17 Escape 2.0L, 31K, Hav ProDS 5W30
Re: Cooling system leak / pressure test question [Re: Billbert] #4692274
03/12/18 09:15 AM
03/12/18 09:15 AM
Joined: Nov 2006
Posts: 20,146
MA, Mittelfranken.de
Trav Offline
Trav  Offline
Joined: Nov 2006
Posts: 20,146
MA, Mittelfranken.de
+1 heat expansion.


ASE L1, Master. Deutsch Meisterbrief.
Re: Cooling system leak / pressure test question [Re: mrdctaylor] #4692335
03/12/18 10:42 AM
03/12/18 10:42 AM
Joined: Feb 2011
Posts: 6,725
Hudson, NH
LeakySeals Offline
LeakySeals  Offline
Joined: Feb 2011
Posts: 6,725
Hudson, NH
AKA Expansion tank.


06 Escalade 6.0L LQ9 AWD 165k M1 5w30
03 Maxima 3.5L POS 152k ST HM 10w30
Re: Cooling system leak / pressure test question [Re: mrdctaylor] #4692339
03/12/18 10:51 AM
03/12/18 10:51 AM
Joined: Oct 2004
Posts: 8,073
Cincinnati, OH, USA
bullwinkle Offline
bullwinkle  Offline
Joined: Oct 2004
Posts: 8,073
Cincinnati, OH, USA
Originally Posted By: mrdctaylor
Originally Posted By: Billbert
Nearly everything expands when heated, different materials expand at different rates and clearances change. Could have been a tolerance stack up problem.


Right. That's my thinking. But by the same token, a pressure test seems to be THE test for cooling systems. Maybe that's a misunderstanding on my part. Unfortunately, at least in some cases it gives a false reassurance that there is no issue. :-/
It is THE test-but many times it's better to test them hot. I had a Ford company van with the 4.6 ('12 E-250) that had this exact issue with both head gaskets-no leak cold, but there were telltale coolant tracks running into the block valley from both HGs. Ford dealer didn't feel like fixing it under warranty, they finally dumped in enough stop leak that the leaking stopped... mad


06 Ram 3500 CTD 4X4(FG Venturi), 93 GMC C3500 6.2, 89 F-450 7.3, 98 XJ 4.0(XG8A), 05 xB(XG3600), 18 Transit 3.7, 03 Merc Grand Marquis 4.6 2V(XG2)
Re: Cooling system leak / pressure test question [Re: mrdctaylor] #4692394
03/12/18 11:52 AM
03/12/18 11:52 AM
Joined: Mar 2014
Posts: 3,322
NJ
Leo99 Offline
Leo99  Offline
Joined: Mar 2014
Posts: 3,322
NJ
I had the same symptoms on my Rav4. Losing coolant. Overflow tank emptying. It was the radiator cap.

Hope your leak is fixed. You're lucky to be vigilant and notice the leak before you lost your water pump and had to be towed or worse and overheated the engine and blew a head gasket.


Without data you're just another person with an opinion. W. E. Deming

2003 Corolla 250,000 miles
2004 Rav4 359,000 miles
2015 Camry 59,000 miles
Re: Cooling system leak / pressure test question [Re: LeakySeals] #4692414
03/12/18 12:12 PM
03/12/18 12:12 PM
Joined: Nov 2006
Posts: 20,146
MA, Mittelfranken.de
Trav Offline
Trav  Offline
Joined: Nov 2006
Posts: 20,146
MA, Mittelfranken.de
Originally Posted By: LeakySeals
AKA Expansion tank.


?? The point was the metal expands not just the coolant.


ASE L1, Master. Deutsch Meisterbrief.
Re: Cooling system leak / pressure test question [Re: Leo99] #4692449
03/12/18 01:00 PM
03/12/18 01:00 PM
Joined: Jun 2003
Posts: 632
McGregor TX
mrdctaylor Offline OP
mrdctaylor  Offline OP
Joined: Jun 2003
Posts: 632
McGregor TX
Yeah, I'd already replaced the rad cap with an OEM one. I'd hoped that was it. He's driven it quite a bit since it was repaired and the level hasn't gone down any. I just hope this aftermarket water pump doesn't start [censored] out like that last one.


02 Tacoma 3.4L, 219K, Magnatec 10W30
02 Trailblazer 4.2L, 179K, Edge HM 10W40
12 Highlander 3.5L, 99K, Napa Syn 0W20
17 Escape 2.0L, 31K, Hav ProDS 5W30

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