MustangMike

I just replaced my upper and lower hoses along with a new rad, fan clutch, tstat, rad cap (water pump was done about 30k ago). The rad hoses are EXTREMELY hard after the engine is warm. They were plenty pliable prior to installation - so it's obvious that the coolant is creating the pressure. Is it ok or do I have some problem somewhere else? I've always assumed that you should still be able to squeeze the hoses at least some, even when there is coolant in them, and I remember them being this way prior to the new parts. I did drill a hole in the t stat to help air get out and it runs cool as far as I can tell, though I've only driven it under 15 miles at a time and in relatively cool air. Should I be concerned???

Thanks!

youngbuck

I don't understand why you drilled a hole in the thermostat. It is designed to function a certain way, and I'm sure drilling that hole is not helping it do that. You don't want your engine to run "cool." You want it to run at operating temperature, which is where the engine is most efficient. Having it run "cool" will definately hurt your gas mileage, and in the very long run may hurt the reliability of the engine.

As far as your radiator hoses not being soft, I'm not sure what's going on there. Maybe somebody else can comment.

MustangMike

Thanks for your concern, youngbuck - but it's a common practice to alleviate the problem of air pockets forming when you're filling an empty system. It's smaller than 1/8" - it will cause no harm in cooling/warming ability.

BTW, I checked the hoses tonight when everything was cool again and they were not hard. I could squeeze them as always. But as soon as it's hot they're rock hard.

GSGALLANT

Are you sure you got the right rad cap? Each cap is rated to maintain a certain system pressure. If you got a cap with a higher rating by mistake, your whole system pressure will be higher, which will make your hoses seem harder when the truck is hot. The cap's rating should be marked on the cap itself. Compare it to your old one to see if it's the same.

youngbuck

Hmm, I've always just burped the system by running the engine with the rad cap off, and squeezing the hoses a bunch... always got any air pockets out for me.

rimpainter.com

Never heard of "hard" hoses before. My upper and lower rad hoses are soft, even when the engine is at operating temp. I purchased them from Toyota.

Where did you buy these hoses?

MustangMike

Thanks guys - good point about the rad cap, I'll check on that. It makes sense that it could be the problem! Hoses came from toyota, I'm not worried about their quality - again, it's a pressure related problem more than anything. Thanks again!

MTL_4runner

The top hose should be pretty hard as the engine warms up and then get softer as the thermostat opens and allows coolant to flow throughout. I would be a bit surprised if both the upper and lower were hard at the same time.

The 3 things I would check are....
1) the themostat opens at the correct temp (old pot of water trick)
2) the rad cap is correct for that vehicle (I assume you got all these parts at the dealer)
3) make sure there are no restrictions from the radiator to the overflow bottle

You can also try the old rad cap (if you still have it) to see if it makes any difference.

MustangMike

Thanks, MTL! I actually checked the T-stat in a pot of water before I installed it, just to be safe. Rad cap did not come from the dealer, that's why I suspect it even more. They were out of them when I was there and being the impatient person that I am, I just went and got one at the parts store. I couldn't get to the dealer today, but you can bet I'll be there first thing monday morning for a new rad cap! (of course I did throw the old one away) The overflow hose seems to be fine and coolant is making it's way into the tank.

Thanks again!

MTL_4runner

Yep, rad cap would be my guess too then.
Let us know how you make out with that after you get the new one.

MustangMike

Finally got my rad cap today (dealer had to order it) - no luck, same problem. In fact, it's gotten a bit worse (even before I put the dealer cap on) - the pressure is actually forcing the coolant out of the top hose where it connects to the block. So it runs down the front of the motor and front cover and makes a mess!

So I'm starting to wonder what is going on. I just drove it home, about 8 miles and felt the lower rad hose when I got here and it was much cooler than the top hose. One would think it's a stuck T-stat - but it's brand new! And I tested it before I installed it, it opened fine, right at 180 degrees! I tested the old one that I took out, and it worked too!!! I'm starting to think that the overheating problem I had (had mentioned in another thread) came from whatever problem still exists. FWIW, I have replaced the fan clutch, rad cap, T-stat, and radiator in the last few weeks in an attempt to figure out why my 4runner overheated on a slightly warm summer day after about 15 miles of city driving. Water pump was replaced about 20k miles ago, as were all belts, hoses, etc. I did check the water pump's function while I had everything apart. I pumped a bunch of water into the engine and had someone start the engine - and fesh water poured out of the t stat housing (without the tstat in there obviously). Is a head gasket issue a possibility? The truck runs perfect as always, no symptoms of a head gasket failure - no smoke, no milky oil, etc. etc. Any ideas???

MustangMike

I should have said, I'm wondering if a blockage is prohibiting coolant flow to the T-stat, which would obviously cause the T stat to not open. Again though, I watched water pour out of the housing after spraying it into the upper rad hose neck. Also, both heaters work fine - lots of hot air!

MustangMike

I've done some checking around with some local guys and the popular vote is that I am beginning to experience head gasket failure. The general opinion is that one is knocked loose or blown slightly, enough to allow cylinder pressure to enter the cooling system. It makes sense, just because an obstruction would not cause the pressure, it would only block coolant flow.

I'm going to do a leakdown test in the next few days to try to pinpoint a specific cylinder. Not sure what I'll do from there if that turns up without anything.

So if I'm going to replace the HG's, should I consider doing a full rebuild?? 144,000 HARD miles on the clock and it's almost 10 years old. I hope to keep it for 1-2 more years, probably another 30-40,000 miles. It runs great right now, no oil burning what so ever. I would do most all of the work myself except for having the machine shop do the normal checks and cleaning. I would probably have them assemble the short block as well. I would do the rest. Any opinions?

MTL_4runner

I am afraid it is sounding more and more like your buddies may be right. You should at least pull all the plugs (look for one or two plugs cleaner than the rest), then do a compression test, followed by a leakdown test and finally check the coolant for traces of exhaust gasses (yes, there is a chemical test for that too). I wouldn't make any assumptions at this point until you did those tests.

MustangMike

Thanks MTL, will do - ordered a leakdown tester today, should have it tomorrow. Already have the compression tester. Hopefully I can take a look at it on friday. Until then, I'm nervous to drive it for fear of blowing a hose off completely, and/or doing more damage than I've already done. Still doesn't make sense why my lower rad hose stays cool - unless the pressure is coming down from the water pump (through the lower rad hose) and up into the rad in the opposite direction of typical coolant flow.

Are home kits available for the exhaust gases test? I've been reading about doing them, but everything I've read references having a shop do it.

Would you rebuild the whole thing if you were me and the HG's turn out to be the problem? Remember, I only want to keep it for another year or two.

Thanks a lot - I'll be sure to report back!

MustangMike

BTW, nice truck - yours is a spitting image of mine.

MTL_4runner

I went back and reread your posts and I have a few more questions for ya.....

1) are both the top AND lower hoses hard as a rock or just the upper hose?
2) is the vehicle overheating at all (you should be able to see the temp rise to about 3/4 on the guage before the thermostat opens and then it should drop to just below halfway)?
3) the radiator flows properly (ie if you use a garden hose and run it through the radiator, there is no resistance to all the water flowing out the bottom)?

I just wanted to make sure that what you are experiencing is not normal because the radiator cap is usually rated for around 15 psi and it is spring loaded so it can build up to that pressure before it allows the coolant to flow over to the overflow tank. The hoses will get harder as the engine warms up and the pressure inside the cooling system helps to keep the coolant from boiling even at high temps. So when you say the hoses are "rock hard" it is tough to quantify that exactly. If you have some hoses that are leaking after you replaced them, you may need to clean the surface better to allow them to seal properly (fine grit sandpaper such as 220/320 can help to create a seal). I am not entirely sure this is a HG issue yet but that is also something to look at. If you can find another 3rd gen to compare to (hardness of hoses when warmed up) that would also help too.

MustangMike

1.) Both upper and lower are. I just went out and started it up with the engine cool. Within 2 minutes, the hoses already have enough pressure in them to hardly be pliable (very pliable when cold/not running). I had drilled a small hole in the tstat too since it was not an OEM unit, so it is possible that pressure can get by the tstat without it being open.

2.) No overheating at all, but I haven't put more than 10 miles on it at a time since all of the new parts, nor has the weather been hot like it was on the day it overheated. Temp guage doesn't make it past halfway. Where is the coolant temp sensor though (I forget). I'm concerned that the engine is actually hotter than the temp guage is reading because of it's location in relation to the pressure problem.

3.) Rad is brand new - put in last week. Can't imagine that there's a blockage. FWIW, coolant does not visibly flow through the rad below the filler neck, even well after the t stat should be open. Coolant just continues to surge up and out of the filler hole - right from the beginning when it's fired up. No change in this throughout it coming up to operating temp. So this is obviously creating the pressure in the hoses that I've noticed. Also, the same symptom existed with the old rad/old parts.

All signs seems to be pointing to compression pressure leaking. All of the symptoms existed prior to me replacing the rad - that's why I did it, I thought the rad was clogged. It obviously didn't fix the problem. I have a brand new toyota cap, new t stat, new hoses, I even replaced the lines to the rear heater core because they were nearly rusted though about 6 months ago. I thought back to the day it overheated, and that morning (the last time I drove it before it overheated), I had been exceptionally hard on it - took it up to redline in all 3 of the first 3 gears (don't ask, traffic around here is miserable sometimes!) It normally gets a good workout from me, but that was exceptional, and a lot to ask for from a 144k motor. As I said, it overheated, that night, on my way home from work. So it would make sense that I did damage to the HG at that point.

As for just how hard the rad hoses are - they literally feel like steel. I honestly don't know how I haven't blown one off yet, I'm waiting to see them ballooning. As I mentioned too - there's so much pressure that it's leaking out of the neck where the top hose meets the block - and I did clean it up prior to installing the hoses using a wire wheel. I remember being able to squeeze the hoses some (and make the coolant slosh around) even when they were hot before any of these problems. Something serious is up. My leakdown tester just got here, so I'll hopefully get to it tonight or tomorrow afternoon.

Thanks again for all of your help!!! MUCH appreciated!

ZUK

iTrader: (1)

I had a similar thing happen. Sounds like all that hose stiffness you have is due to a headgasket. The surging of the fluids out the cap while cold reinforces that.

MTL_4runner

Well Mike, after reading your last response, I am going to have to sway back towards it being a HG issue (esp the fact that the hoses are hard even when cool, the fact that it severely overheated just prior to this happening and that you have replaced almost everything in your cooling system already).

To answer your previous question on the combustion leak tester kit, yes, there are a few places to get them (NAPA being one):
http://www.arrowheadradiator.com/hea..._leak_test.htm

.....check a few local auto parts chains to see if they carry these.

If you do in fact have a blown HG and you only intend to keep the vehicle a little while longer then I would only do the HG and forget the rebuild. If you are going to go that route, then just get a used motor and be done with it (you can sell the rest for parts on eBay to recoup as much money as possible to offset your motor costs).