overheating issues

[BlackBart]

No rattle when I tap, the thing ain't movin at all to shake it though. It's got three ubolts on the front end and two on the ass. Friggin solid.

 

I am entirely against dealing with decrepit exhaust bolts if at all avoidable, so I figure I'll wait til this gasket sealer cures and see how the tstat replacement truly affected the thing.

 

Nothing to do til then but read more ratsun walkthroughs.

 

Did I mention how awesome this place is?

[lctmjw]

Once you're sure the cooling system is leak-free, there's not too much else to check that hasn't already been covered. Water pump function, rad cap holds pressure, thermostat, hoses in good shape/not collapsed, heater core function, ignition timing, fan and clutch operation. I mention clogged cat because it often gets overlooked, but it's a longshot. Also, how much oil is getting burned? Rings often fail from tension loss after an overheat condition, may explain oil consumption.

[BlackBart]

Burned about a quart in 500 miles.

 

I'm thinking of starting an abuse test thread. See how long I can btfoo (beat the fork out of) this already abused rig.

[lctmjw]

Also, make sure the system is free of air. I like to elevate a vehicle till the rad is the absolute highest point, fill/top off with the engine running, rad cap off, for 20 minutes or so. Then cap it, drop it, and roadtest. Not really a problem with these trucks since the radiator sits up tall, but my Supra was a real pain. Rad sat low and the high point of the cooling system was the turbocharger, required a lot of front end lift and patience.

[lctmjw]

Burned about a quart in 500 miles.

 

Jeez, that's like a quart every not quite two fillups.. Seems it would be smoking like a chimney burning that much oil.

[datzenmike]

Shroud is good, fan clutch seems pretty packed still. Changed thermostat this morning, went for a drive and she still getting too hot. Limped home and found a pretty steady couple drips at a time coming out the new stat gasket. Thought I did everything by the book except applying silicone sealer.

 

Old tstat was burnt looking. Mightve been 10-15+ years old. No "jiggle valve" on it either. Rad looks relatively dirty inside, but I've had dirtier ones function properly on 80's fords. There was a decent bit of pitting on the stat housing and cover. Sanded out best I could, but I'm wondering if this leak wouldn't make temp climb as well...

 

Any more thoughts for an idjit?

 

 

Some of this you have already covered...

 

Lets assume the engine tune is not the cause for a minute.

 

This leaves lack of air or lack of water flow/heat transfer to the air.

 

Poor air flow...

Do you have the fan shroud in place? Shrouds increase the fan's cooling efficiency.

 

Do you have a clutch fan? It should turn by hand but be very firm to turn. If loose, the silicon oil has leaked out and the fan will not reach it's intended 1,500 RPMs @ 4,000 water pump pulley speed.

 

Fan blades broken?

 

Are the rad fins plugged with road debris, leaves and bugs?

 

Are fins missing from the tubes? damage?

 

 

Poor water flow...

If tap water is used crusty hard water scale deposits will clog the rad tubes. Open rad cap and look. Use only distilled water and a good antifreeze/coolant.

 

Look at lower rad hose while revving the engine... does the hose collapse from water pump suction because it's too soft? Hoses rot from the inside out and my look fine.

 

Have you by-passed the heater core by joining the two heater hoses? This is a no no as the water going through the heater (now missing) is not going through the rad and returns to the engine still hot. Just block the flow somehow.

 

Fan belt slipping or oily/damaged?

 

Is there unexplained coolant loss? Head gasket may be blown or blowing compression into the cooling system and over pressurizing it and expelling water..

 

Most common problem is faulty thermostat. Don't waste your time testing... you have to remove and replace the gasket anyway... replace with a new one. No $3 WallMart crap, spend $10-$12 on a good quality one.

 

Trapped air is not a problem, just drive it and it will burp into the rad as soon as the thermostat opens. Don't forget there is a water pump pushing coolant through everything (even a water cooled turbo) and air just gets pushed along until it gets to the rad. Check the rad level once cool enough and top it up.

[BlackBart]

Can't even tell if changing stat did any good or not cause it's still leaking out the flippin gasket. Rtv was useless, went to town, got another gasket, installed...still just drips right out of there.

 

I'm lost.

[lctmjw]

Personally, I would skip using RTV silicone in conjunction with the gasket, or at all in this application. The gasket by itself should be all you need, provided the metal surfaces are good and clean and it's screwed together snug enough.

[datzenmike]

Possibly cracked cover or the housing?

 

Tape some sandpaper to a sheet of glass and rub the thermostat cover back and forth to remove irregularities in the casting. If you can get the thermostat housing off the head, you can do the same to it.

 

Get a dollar store hole punch and you will never want for gaskets again.

 

 

 

 

Pursuing a sweet coolant smell I found one of the thermostat housing bolts broken off. This absolutely figures as most previous owners didn't pay much for the car and don't want to spend the time and money to fix right. So try as hard as I could I broke the short bolt off. The bolts get stuck in the housing and not in the head. I couldnt pry the housing off the bolt ends so I sliced into it.



Bolt ends now almost twist out by hand.



The replacement housing was the same. Broken bolt. Drilled out the stuck bolt.



Had to make my own gasket. Installed the housing but first I dipped the bolts in lithium grease so they won't stick in the housing again.



Oh yeah, the thermostat? A 160F can you believe it? These motors were designed to run 25 to 30 degrees warmer for best economy and performance. 160F thermostats are so 1950. This is so wrong headed. It get's a new 185 tomorrow.

[BlackBart]

Upon closer inspection it's coming from directly underneath on the "housing." Only the housing appears to be connected to the rest of the intake manifold, not individually removable like the one in your picture.

 

So I might venture a guess that I cracked the housing/intake around the bottom bolt when I overtorqued it...? Sure wasn't doing that before.

[datzenmike]

Yes... I see now that this is A 720. maybe complete your profile with what vehicle you have. I didn't look hard enough. :lol:

 

7-9 ft lbs torque on the thermostat housing bolts. They aren't that big.

 

Take the thermostat cover off and have a good look. At least it's easy enough to get at. Looking at the one I have the top bolt is the most fragile and least supported. The thermostat is hard to center in the intake and set the cover over mounted on it's side. Easy to pinch the thermostat on the gasket and not seal. Have a look.

[BlackBart]

Eureka, hoss, that did it. I tried to pinch it in place through the covers tube while hand tightening the bolts, seems like progress. Where I had a decent spurt when throttled and a drip when idling, I now have a drip when throttled and basically nothing when idling.

 

Here I was thinking about new manifold this, and junkyard that!

 

https://m.flickr.com/#/photos/143334550@N05/28399308152/

 

Thats my new rat. I like this thing WAY more than the 93 d series I had. Maybe junkyard later just for fun. \0.0/

[datzenmike]