Overheating Engine - Blown head gasket or pump?

[Skifey]

Maybe there is some build-up/corrosion on the outside of the housing.
Maybe the silicone hose is cut by the hose clamp. Personally I'd ditch them & go rubber.

Don't tell me that - I just bought the Silicon hose kit! Damit haha!

the housing has a little lip on it. Judging by the distance you have the clamp from the end of the hose, I'd suggest you have the hose clamped on the lip instead of the flat surface next to the lip. Hence why you cannot get a proper seal.

Tad bit confused here sorry; does the clamp need to move further away from the engine or closer to it? Forgive my being an amatuer

When I take that hose off to readjust it and get a better seal I'm assuming coolants going to go everywhere since there'll be plenty sitting in the engine above that point, am I right? And if so, is there any better way to fix it and get a proper seal without making a complete and utter mess?

Look at me go, I'm full of questions! Would everyone agree this here is my problem and not a head gasket? I'm somewhat hopeful that I can avoid the costs of dealing with the head at this stage since I've found this leak. I don't even fully understand how a leak can cause overheating besides a low coolant level or is that exactly it?

[hks_kansei]

A leak can cause overhating for two reasons.

one, coolant getting too low and not able to remove heat from the engine.
The coolant essentially acts like a heat sink, it absorbs heat and transfers it to the radiator, where cool air then flows past fins etc and makes the coolant cool again, where it then passes into the engine to absorb heat again.

Less coolant means less ability to absorb heat, and also air pockets that can allow boiling, which further reduces ability to absorb heat.
The leak also allows pressure to escape, and pressurised coolant/water has a higher boiling point.

so yeah, fix the leak and see what happens.


regarding the clamp, try loosening it, moving it closer to the engine, and then tightening it.

see how the pipe in the pic has a smooth part, then a bump at the end?
the hose clamp should be positioned to clamp down on the smooth part, the bump it only there to stop the clamp from letting the hose pull off.
It looks like you have the clamp on the bump, which isnt ideal (harder to tighten properly, less area to seal, and also means the hose can more easily come off)





with regards to head gasket, it's probably fine, but if you keep driving while an engine overheats you can sometimes cause them to fail (usually the thin sections between cylinders go first, as they're the weakest point and cop a lot of heat)

[RS2000]

When I take that hose off to readjust it and get a better seal I'm assuming coolants going to go everywhere since there'll be plenty sitting in the engine above that point, am I right? And if so, is there any better way to fix it and get a proper seal without making a complete and utter mess?

If the clamp is sitting on the lip of the housing (good pickup by project.r & hks), initially try just slakening the clamp right off, & pushing the hose on as far as it can go - it can only go to the right angled bend. Put the clamp mid-way between the hose end & the housing lip, & square to the hose.

[Skifey]

Quick update for all of those who are still checking in - I appreciate all of the help so far everyone, truly!

I fixed the leak last night, corrected the coolant/water ratio and tied everything back up again. Drove it this morning with no issues up until a tad bit of traffic after getting off the highway and noticed it was running just a tad hot, maybe 1o'clock. Luckily I was already at my destination so didn't get to see if it was stable or going to continue. After I parked, no leaks, no nothing.

I'm going to run a compression test this afternoon, time permitting, as people have suggested and see what that yields. Tap back shortly ladies and gents!

[Guran]

Even brand new thermostats can stick closed. I've had lots of issues with them. If you're still getting any overheating, try removing the thermostat, burp out the air, and drive without a thermostat. The engine will run cold at cruising speed and should come up to temperature when under load (up hills) or in stop/start traffic. If the water pump is OK it won't overheat.

[StillIC]

Even brand new thermostats can stick closed.....

Yep. The only failed thermostat I have ever had was a brand new one in a Datsun L series engine. I had various engine bits apart so replaced the old thermostat because it was old, the new one cheap and I could. The new one failed straight away. I took it out, tested it in a saucepan on the stove, and yep, it didn't open at the temperature it should.

EDIT: My Gregory's manual for the L series said to test the new thermostat before installation. I should have followed instructions. Since then I sometimes have saucepan tested brand new ones, but have not had a failure since (in ummm, 20 something years).

[manga_blue]

I'm going to run a compression test this afternoon, time permitting, as people have suggested and see what that yields. Tap back shortly ladies and gents!

Compression tests are often inconclusive when trying to diagnose a blown head gasket. The standard test these days for a blown head gasket is a CO test. Basically a blown gasket lets high pressure gas, containing carbon monoxide - CO, make its way from the combustion chambers into the cooling system. Most (all?) local garages have test kits to detect the presence of CO in the coolant, usually at the top of the radiator.

My local does the test for free - mostly because they're usually the ones who get the work. The test takes about one minute and from memory costs them about $5.00.

[greenMachine]

My go-to method:

If the radiator is full, and has been burped properly (no air in the system), leave it idling with the radiator cap off. If the head gasket is leaking, you will get sizeable bubbles exiting via the filler. Keep topping it up in that case, to confirm that it was not just an isolated pocket of air in the system, and to make the bubbles easier to see. Obviously, if the bubbles keep coming, there is a problem, the bigger/more frequent the bubbles, the bigger the problem. Pro tip: one of those big yellow filler funnels makes the job a lot easier.

I have heard of the CO test Manga mentioned, but have been told that it is not reliable, FWTW.

[Skifey]

Thanks again for all the info fellas - never thought to stove test a brand new thermostat... looks like im going to have to refill the whole car... again!

I've done a compression test today just for piece of mind and I was actually surprised at the results. Numbers from back (closest to firewall) to front were 120, 122, 125, 127 which I'm assuming and hoping are numbers you want?

Car still though is overheating mildly although I've just been turning the fan and heat on max without A/C and it stays at 12 on the dot.

When I first installed the radiator I ran it without the cap on up to operating temp and topped it up. I didn't really see any bubbles come out and I haven't properly burped it yet aside from squeezing the radiator hose that was previously leaking with the cap on and engine off. That'll be my next port of call I think.

On that note; I did notice something when I was fixing that leak. When squeezing the lower radiator hose with the cap on what I'm presuming to be the water pump was rattling. Or like it was turning noisily. Is that normal? Should there be mechanical noise when you squeeze the pipes?

[NitroDann]

If you did it with a full battery or a jumper pack, and with the throttle open you'd hope to see 160 or more. That's the typical procedure.

130 is around the mazda factory service manual "do a rebuild" recommendation.

Dann

[Skifey]

If you did it with a full battery or a jumper pack, and with the throttle open you'd hope to see 160 or more. That's the typical procedure.

130 is around the mazda factory service manual "do a rebuild" recommendation.

Oops... I did it with the engine cold and no throttle. Good battery obviously

[NitroDann]

You're testing air pressure, gotta let it get inside there.

Dann

[Ronin]

I had a similar overheating problem, it would do it sporadically in traffic.
At speed, with air passing through the radiator, temps would be fine.
With the aircon on, temps were fine ( air con fan was pushing air through the radiator ).

The problem was a bad connection to the radiator fan,
Namely the plug was bad.
This meant that when the fan was supposed to kick in, sometimes it would, more often it wouldn’t.

[Maverick]

Quick update for all of those who are still checking in - I appreciate all of the help so far everyone, truly!

I fixed the leak last night, corrected the coolant/water ratio and tied everything back up again. Drove it this morning with no issues up until a tad bit of traffic after getting off the highway and noticed it was running just a tad hot, maybe 1o'clock. Luckily I was already at my destination so didn't get to see if it was stable or going to continue. After I parked, no leaks, no nothing.

I'm going to run a compression test this afternoon, time permitting, as people have suggested and see what that yields. Tap back shortly ladies and gents!

Pressure test your cooling system.. you can also run your engine with pressure tester connected to check if head gasket has failed..
Cheapest option...


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