Overheating Engine - Blown head gasket or pump?

Skifey · Postby **Skifey** » Wed Mar 28, 2018 5:20 pm

Hey guys,

So this one's been a long time coming but I'll try to summarize as much as possible. It's a 1990 NA with a 1.8L transplant done very neatly. No idea how many km's on the engine or build date. It's also my daily and I do about 70kms on it a day majority of which is highway however the morning is always stop-start traffic for 15-20minutes.

About 2 months ago I noticed the car was overheating in the morning highway stop-start traffic. I didn't think much of it at first and kept driving it to work trying to figure out what conditions made it overheat. Straight up I won't lie; it's gone well past 2 o'clock on many occasions (over 10 times I would say) and all the way up to the 'H' twice at which point I drove it maybe a minute or so more to pull over safely before shutting it off. Dumb, I know.

Took it to a mechanic in between all of this, he did the dodgy; replaced the radiator fan which was broken, did a coolant change and sent me on my way. Car overheated again within 30 minutes of driving.

Fast forward 1 month (27MARCH) and I've just installed a Mishimoto performance radiator, fan shroud, replaced all the hoses and thermostat. Also put new coolant in it. Only thing worth mentioning is that I didn't have enough distilled water in the house to fill up the overflow reservoir. Thought I was a god in human form and that all was fixed. Nope; car overheated again this morning on the way to work so I'm left wondering and can only arrive at 2 conclusions; water pump or head gasket.... or I've completely f***ed the motor by driving it hot here and there for 2 months....

If anyone at all can throw some criticism, constructive or otherwise, advice, prices for fixing or anything at all really at me right now I'd appreciate it because I am clearly well in over my head - cheers!

EDIT: It's worth mentioning that the car doesn't overheat whilst travelling at highway speeds nor really whilst just cruising at 60km/h. It only overheats once I've been doing the stop start for a good few minutes and turning the heat and fans on max seems to keep it at just past 12 o'clock.

hks_kansei · Postby **hks_kansei** » Wed Mar 28, 2018 5:37 pm

The fact it doesn't overheat at speed say a it's about airflow or coolant flow

Starting cheap, do the thermostat, might be sticking.

Otherwise, look at the pump for leaks/worn impeller, or a blockage in the system.

Head gasket will often show up as leaving water in the oil, so check there too.

Locutus · Postby **Locutus** » Wed Mar 28, 2018 5:45 pm

Have you verified that the fan turns on with the car idling in your driveway? If the fan is working I would start with the thermostat.

In any case I would stop driving it to work unless you plan to rebuild it replace the motor in the very near future...

MX593 · Postby **MX593** » Wed Mar 28, 2018 5:55 pm

Check the fan. Just unplug it, run some 12v power to it to see if it runs.

Postby **NitroDann** » Wed Mar 28, 2018 6:05 pm

Its probably the thermostat.

Dann

Skifey · Postby **Skifey** » Wed Mar 28, 2018 6:26 pm

Just replaced the thermostat with a brand new Tridon TT323-180 along with the corresponding gasket last night and I tested the new fan shroud as well. AC fan turns on when the AC is on and the standard fan turns on when the car reaches operating temp.

I haven't seen any leaks coming from the engine nor any water in the oil. To be fair I wouldn't really know where to look or what water in the oil looks like.

I've done a bit of googling and the general consensus seems to be that if you drive the engine hot you can make the head 'soft' which entails a replacement or rebuild and that's what's got me 'shaking in my boots'. Am I right in thinking - given the amount and duration I've dríven it hot - that I really well and truly have damaged the block already regardless of the overheating issue as it now?

Postby **NitroDann** » Wed Mar 28, 2018 6:36 pm

What youve told us is way to vague to give a definitive answer.

You will need to pull the water pump or swap the motor probably by the sounds of it.

Dann

greenMachine · Postby **greenMachine** » Wed Mar 28, 2018 7:42 pm

Burping these cars is an art. If all the air is not flushed out of the cooling system, it will almost inevitably overheat. How confident are you that it was properly burped?

Overheating can cover a broad range, from a high gauge reading, to sitting there idling pumping steam and coolant out from the radiator cap/overflow. How bad was yours in terms of drama?

Do a compression test, to check for blown head gasket. If that does not show a problem, a new water pump would be the next step. And do a long thorough burp when complete.

Good luck

:mrgreen:

Skifey · Postby **Skifey** » Wed Mar 28, 2018 8:02 pm

UPDATE! Left work shortly after my last post and before I left I popped the hood to have a brief check over things while it warmed up. Water/coolant level in the radiator had dropped since I filled it to the top last night when I did the radiator install. I topped it up with some distilled water and also filled the overflow reservoir. Got in and started driving home and sure enough it overheated again in a bit of start - stop traffic but ONLY after a good 5-10 minutes of doing so and only just got past 12 o'clock before I turned the heater and fan on max which stopped it from going further. After that, got back up to highway speed and no dramas for the entire ride home.

Got home and left it running in the garage and BADAM!! I found a rather unhealthy leak on the passenger side of the engine. I did my absolute best to find the source but naturally I couldn't pinpoint it without getting burnt. By my best guess? It was dripping from the underside of the lower coolant hose (that I just replaced last night!) going into the engine. However that could just be drip down from a higher point. I'd say it definitely appeared to be coming from BELOW the head gasket sooooo safe to say I'm a bit bamboozled but again... hard to see with it being hot and cramped. Might be possible that I didn't put the hose on properly but I doubt it, I'll post again as soon as I have time to pull it apart tonight once it's cool.

Is there anything else other than the head gasket and lower radiator hose on that side of the engine where it could leak from? If not I'm forced to assume it's one of the two because the water pump is on the front if I'm not wrong?

What youve told us is way to vague to give a definitive answer.

Apologies Dann

Burping these cars is an art. If all the air is not flushed out of the cooling system, it will almost inevitably overheat. How confident are you that it was properly burped?

Overheating can cover a broad range, from a high gauge reading, to sitting there idling pumping steam and coolant out from the radiator cap/overflow. How bad was yours in terms of drama?

What on earth is burping? Is that bleeding air out of the system?

project.r.racing · Postby **project.r.racing** » Wed Mar 28, 2018 9:54 pm

Burping is queezing the lower pipes using extra pressure to push the trapped air in the system out the rad fill hole. If you didn't do this, it is probably the reason for the overheating.

RS2000 · Postby **RS2000** » Thu Mar 29, 2018 11:18 am

Is there anything else other than the head gasket and lower radiator hose on that side of the engine where it could leak from? If not I'm forced to assume it's one of the two because the water pump is on the front if I'm not wrong?

It's probably your lower radiator hose not clamped tight enough, but if the same as a NB8A, there is another spot to check:
Just above & forward of where the lower radiator hose attaches to the back of the water pump, is a bypass pipe. This pipe runs back under the exhaust manifold to a cabin heater hose. The front of this pipe is sealed by an 'o' ring.

When refilling the cooling system, I find the best way to prevent air entrapment is leave the top radiator hose disconnected at the thermostat housing. Fill slowly thru' the radiator neck, & the air in the system will escape via the thermostat jiggle pin. Eventually the coolant will come thru' here too, & flow out the thermostat housing, then refit the radiator hose.
With the radiator & expansion tank filled, run the engine until hot & run at 2000rpm for a few minutes. After cooling, you may need to slightly top up the rad or expansion bottle.

hks_kansei · Postby **hks_kansei** » Thu Mar 29, 2018 11:56 am

God I hate that bypass pipe.

The MX also has a few tiny hidden coolant hoses that often get forgotten when replacing them.

Like the ones to the oil cooler, the tiny one under the throttle body, the bypass pipe o-ring, and a few other little ones you cant really see (that bloody capped off one on the back of the head too!)

Skifey · Postby **Skifey** » Thu Mar 29, 2018 11:59 am

Just above & forward of where the lower radiator hose attaches to the back of the water pump, is a bypass pipe. This pipe runs back under the exhaust manifold to a cabin heater hose. The front of this pipe is sealed by an 'o' ring.

Burping is queezing the lower pipes using extra pressure to push the trapped air in the system out the rad fill hole. If you didn't do this, it is probably the reason for the overheating.

That's super useful info, thanks to the both of you RS2000 and project.r.racing

I've attached below a photo (since the video wouldn't upload) of the leak in action. And yes, that's it SPRAYING out, not just dripping out and this was 2 minutes after I'd shut the engine off this morning. Since I had adequate light this time I'm gonna go out on a limb here and say that it definitely looks like the lower radiator hose? How tight does the damned thing need to be though? It's not like I didn't screw it down :roll:

RS2000 · Postby **RS2000** » Thu Mar 29, 2018 12:09 pm

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.

project.r.racing · Postby **project.r.racing** » Thu Mar 29, 2018 12:23 pm

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. The clamp should only be 2ish millimeters from the end of the hose.