New hose or new engine? Coolant loss and overheating. (1 Viewer)

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Feb 15, 2019
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Update/solution: I found that I had an aftermarket radiator cap with an out of spec pressure rating. I bought an OEM replacement, and it's been running awesome ever since. What appeared to be happening was radiator cap was not functioning properly either because of the pressure spec or something else, and a few mils of coolant would leak out here and there. Over time that led to a significant lack of coolant that I did not catch until it became a problem, causing overheating under load. Thanks for the insights to help figure this out.

I've been spending quarantine casually trying to track down what's wrong with my car. I think I found out the bulk of it today, but I'd be grateful for feedback and thoughts.

The short of it is:
- I have a confirmed coolant leak, currently not leaking
- Car started running hot
- Refilled coolant, levels dropped after driving with no leak present
- Coolant levels stabilized
- I think I lost coolant to the leak, and that after refill, levels dropped from burping, and that I do not have a blown HG.

And the long story is
I took my 97 out to the desert back at the end of February. After about 2.5 hours in the car, when I got into town the AC shut down, but I did not see the needle move. On the way back, with AC off I started getting close to redlining up a steep grade.

I'd had fan clutch on my list for a while, so that was replaced when I got back and thought that'd be the end of it. However around town I started overheating at low speeds, with the new fan clutch. I noticed around then I had a leak just behind the driver side wheel. I caught some in a bowl and it was red/pink. At first I thought steering fluid, given a whirring I developed and needed to top off, but I'm certain it was Toyota Red.

At this point (not when the AC went off in the desert, not when I overheated coming back, not before replacing the fan clutch) I checked coolant levels. You could see radiator fins. I ordered some Toyota coolant, and topped it off. It took about half a gallon at first.

I drove around the neighborhood, everything was fine. I come back later, no leak. However coolant was low, this time about a quarter gallon.

I called my mechanic and asked about what an engine rebuild looks like, at this point being convinced it's HG. They said don't get carried away yet, that's a lot of coolant to be burning up with no symptoms, leak or no leak visible. And they knew about the previous coolant leak, and suspected PHH.

I drive again, no leak, coolant low about an eighth of a gallon. I drive again, no leak, coolant low this time a tiny bit. Drive again, no leak, coolant at the right level.

My current diagnosis is a leak, probably PHH, that over time diminished coolant levels enough that I'd approach overheating under certain conditions (high stress, low speed). This led to air in the pipes and burping as I drove it and added coolant until I reached my current stabilized levels. The leak is currently not leaking, but a pressure test should narrow it down. No new engine today.

Curious what you all think, if I'm missing anything important. I figure I need a new engine some day, and I'd rather not have it happen on a trip, so if I'm biasing thinking toward the simple/low cost solution, I'd rather learn it now.

Thanks in advance.
 
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Joined
May 13, 2019
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Alaska
Rent a block tester from your local auto parts store. That will let you know if you have an internal leak in the engine.
 

Tachycardic

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Any coolant sprayed around in the engine bay? I had that problem and it was due to an old radiator cap. Pressure testing did not identify the leak; it only happened when the engine was warmed up. I replaced the cap and all is good now.
 
Joined
Dec 14, 2018
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Silverthorne, CO
If its a leak behind the driver wheel well my bet is throttle body coolant hose. Mine would leak like mad when cold and stop as soon as it was warmed up. Coolant can drip onto the engine block and evaporate before it hits the ground.
 
Joined
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San Diego
Thanks for the sanity checks. I was half expecting a bunch of posts just saying "HG" as I've seen on other threads, but sounds like I am in the clear at the moment.

I'll check out all the suggestions. Interestingly, it's not leaking at all now, and coolant levels have been stable for the last few rides. What you said KC about throttle body coolant hose is really sounding like the top candidate, potentially along with PHH. Will follow up with the leak test and assume radiator cap is the new target if it comes out negative.
 

Tachycardic

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I went thru 2 pressure tests and no leak was detected. I only lost coolant when the engine was warmed up. There was coolant spray in the anterior compartment of engine bay with some pooled up on the tuna can. Not saying that it is the cap, but if you still have the original cap, it'll only cost you $15 and a twist of the wrist to see if it resolves the issue. OEM Radiator Cap
 
Joined
Mar 27, 2015
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Westminster, CO
Could've had air in system. Are the hoses hard with pressure when it's warm?

Best thing to do is pressure test at 17 psi. Rent the tester from autozone.

Check rear heater for leaks

Check that the radiator cap tabs are bent enough to hold the cap down. Just bend s little and try.

I just went through this and it was the cap. Even the new oem cap was not bent enough to seal.
 
Joined
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San Diego
I think you're all right, with both problems (cap and a leak).

I haven't driven it in a few days, but I saw that it was leaking a fair amount of coolant under the driver's side of the radiator. A wet puddle on top of a dried puddle, I guess the day before.

I open the cap to see how much I'd lost, and to the contrary, a few ounces of coolant came gushing out. It was giving me trouble putting it back on, it didn't want to smoothy go into place like normal. Why I only notice this now, I don't know, seems odd that this would be new.

I looked at the overflow wondering why it didn't prevent the gushing, and saw it was right exactly on the line, and realized that it's always right exactly on the line any time I've looked at it. I'll confirm this more carefully. Wish I had put 2 and 2 together earlier.

So current thinking, radiator cap is busted, preventing excess volume to go into overflow. High pressure finds weakest link under current conditions (PHH/throttle body coolant hose before, radiator/lower radiator hose).

Next step is a new radiator cap and a pressure test. Thanks for the feedback, been very helpful.
 
Joined
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Silverthorne, CO
Was the engine warm when it shot out coolent after the cap was removed? The bit of tube running to your reservoir may be clogged.

If the system is remaining pressurized when cold id definitely change out the cap. Normally I hate throwing parts at a problem but a cap is so cheap it makes sense to try that first.
 
Joined
Feb 15, 2019
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San Diego
Was the engine warm when it shot out coolent after the cap was removed? The bit of tube running to your reservoir may be clogged.

If the system is remaining pressurized when cold id definitely change out the cap. Normally I hate throwing parts at a problem but a cap is so cheap it makes sense to try that first.

Cold for days. Doing as advised, and trying to think about what problems might rear up once the new cap is in place. Anecdotally, I've heard of it causing other leaks to go into overdrive. But considering it seems like we're going from high pressure to the right pressure I'm hoping that's not the case in this scenario.

In the meantime I'll check on that tube you mentioned, good call.
 
Joined
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replace the phh, do a pressure test on the cooling system and replace the rad cap. rad cap is cheep enough that it should be replaced if your having any sort of cooling problems
 

MoJ

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If it’s leaking cold this isn’t rocket science. Grab a flashlight and follow the leak. If needed strategically place paper towels and note observations about which is wet. Are your hoses original? Is the radiator original?
 
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