My 93 Max has a puzzling problem - there seems to be very weak pressure at the upper hose going into heater core in the cabin. I put there T-fitting with the valve (only on upper leg of the T) and clear hose in hope to get rid of any trapped air there. The problem is when I start the engine and open the valve there seems to be no pressure in the system when it's cold so no coolant goes up the clear hose. When engine is at the normal temperature it also doesn't go up, only if I squeeze the upper hose by hand I can see some coolant going up into clear hose. If I rev the engine the coolant actually goes down contrary to my expectations.

What could be the problem?

If the heater core was clogged it wouldn't prevent coolant to go to the clear hose as T fitting is mounted even before the stock valve on the upper hose. I also tried running water through the core and it didn't seem to have any problem. This is of course assuming the direction of circulation is from the upper hose through heater core and then back into the engine by the lower hose.

 

Viking has done a very nice dedicated color flow diagram form the manual here http://www.cardomain.com/ride/748507...ockholm-se?p=8............. and as for differential pressure in the cabin heater - I suspect you need very little pressure difference to actually circulate the water through and its probably only going to start happening when you hit 1500+ rpm?

Does your engine have any cooling problems?

 

No, the temp stays slightly below middle even on hot summer day (+30C).

What puzzles me is when I rev the engine coolant in the vertical part of the T fitting goes down - Bernoulli effect? Probably it actually signifies that as speed of circulation increases the pressure goes down. If that's the case then it means circulation wise it's working as it's supposed to. OTOH if the working pressure in the system is say 5psi it roughly corresponds to 3m height of water level to compensate and in my case it doesn't come higher then 1 cm... Radiator cap?

The actual problem I'm trying to solve is not hot enough air coming out of vents in the cabin. It gets better after engine warms up but long after it reaches normal temperature. Typically it would reach normal temp after 5 min but air becomes hot only after 20 minutes or so. It will also depend on rpms, getting just warm at idle.

 

If you have checked the actual in-cabin heat exchanger for blockages as you say and found no problems, then I guess its possible that some of the passages in the head/block are blocked (stagnant non-treated coolant causing deposits?)

The location of the in-cabin circulation ports on the block/head is normally chosen so that actual pump circulation pressure gets used to get the coolant moving through and not only a simple venturi design.

I would remove the in-car hoses from the head/block and start poking around with a sharp object to see if you cannot by luck dislodge some blockages that can be reached.

With those hoses off, start the motor when warm and see how much flow you actually get out there while keeping the radiator filled with a garden hose

Radcap is not the problem and I don't know what sort of pressure the pump can create in the cooling system, but 5psi sounds high if I have to judge from the flow seen through the radiator - guess its always possible that the pump is simply up to maggots since the 3rd Gen's cooling system is IMO very nicely way over designed (much appreciated though)

 

Thanks for the ideas, I might try it next weekend.

One more thing - my coolant always looks 'dirty'. First, I thought because of the application of some 'stop leak' by the previous owner as it got that color after the application but it didn't clear up after complete engine replacement and several flushes. I fill it in with clear mixture and it comes out to expanding tank looking like I washed dirt bike with it. Never seen white smoke out of the tail pipe or coolant in the motor oil. Do you think I should pressure test it (low pressure, say 3 psi) just to see if it can hold it?

BTW, if the cooling system operates at 115C then this fact alone should cause pressure increase by at least 4 psi at normal operating temperature so I should observe either steam or boiling coolant coming out of my T fitting. OTOH even slight change in volume would relief that pressure. I should probably fill the hose coming out of T with coolant say 10 cm high, start the engine and see how pressure changes with temperature. That could serve as my pressure- test manometer as well.

 

Dirty coolant means stop whatever you are doing or trying and sort that first - remove hoses/prod/flush/turn upside down/whatever but until your rad and overflow stays clean chances are you have rubbish sitting somewhere not only causing a blockage but also negatively impacting the cooling action of the engine.

Stop leak contains material in suspension to block leaks - if that stuff is not located in an actual leak its either still circulating (best case) or its parked-off in a hole you actually want open or unrestricted.

If you are not losing any liquid its IMO senseless to do a pressure test.

True about the 115C temp causing a 4psi absolute (imo quite a lot more in a sealed system) but that is not what the waterpump is doing - the WP is creating a differential pressure (or then at least trying to anyway) within the already pressurized coolant in order to affect coolant circulation - its got absolutely nothing to do with the static pressure as a result of the actual coolant temperature. The reality is that our water pumps are little more than a bunch of spoons stirring the coolant very fast and the differential pressure the waterpump can create is very close to zero because both the intake and outlet of the pump is working with non-compressible liquid in the same space and the pump design is not a positive displacement design.

As for seeing steam or liquid coming out of your T if its left open (that is what you are suggesting?).................... if its left open the cooling system cannot possibly pressurize so you will not measure any pressure increase as such - what you will be seeing is the coolant expanding due to heat and then eventually when the localized spots inside the block and head start producing bubbles inside the coolant due to lack of coolant pressure, the T will start spewing liquid.


As reference:

This AM it was 18C here - when I got in the VG, I moved the heater control and fan over to max and started the engine .................. about 200M down the road I could already feel heat coming out the vents before the engine temp gage needle even reached the bottom line - about 500M further and I started getting serious heat out of the vents with the gage sitting around 1/4 scale - about 500M further and temp gage was at normal just below midpoint position, and I had serious heat coming out of the vents.

 

just in case....lets start easiest to check first

is your fresh air vent lever open?
its on the left side of the controls and flips up and down
listen carefully for the flap door open close sound
to rule out a broken lever-to-vent door cable

also there is a coolant air bleed 10mm bolt on the upper intake
good luck

 

thanks I was hoping to see some coolant rising in the pipe, not really a stream mostly due to coolant expansion. I guess it is easier for the coolant to go to expansion tank first as it is lower than my T fitting.

You must be driving in 1st . Thank you for the reference, I'll check it out. Recently it was +5C and it took me approx 4 km to get the gage in the middle. I was getting only 'some heat' by then. What doesn't make sense to me is that it takes another 15 km to actually warm up air flowing out of vents to the acceptable level. All these 15 km the gage stays at the same spot. It's almost like something needs time to expand and let the coolant flow. It also depends on the rpms - at idle the air flowing out of vents becomes cooler while it gets warmer at 1.5k and up.

 

-closed
- it's auto climate control unit, so the lever is on the top-left side
- thanks, I'll try

- I live around that bolt .

 

Coolant can only get to the expansion tank once the radcap pressure has been reached and the radcap valve opens - with your experimental T setup and the coolant effectively only in a non-pressurized state, there is just no way that is going to happen at all.

Nope, but my coolant is clean and the spoons on the pump are stirring merrily thanks................. and ambient was 18C.

You really need to remove the hoses to the cabin from the engine, start and rev the motor while keeping the rad full with a garden hose like I said before - we know you have a problem but you need to start eliminating stuff and that is the absolute easiest thing to do .................. if that is not the obvious answer then maximagician's concern is the obvious answer - ie - your cabin control system is funky.

 

makes sense, it's just the tank get filled as a result of expansion but if I open valve on the T connector the coolant doesn't shoot up - nothing comes up actually. I guess, there's no reason to - not condensated steam is hard to see and there's no extra pressure in the system left when valve is open and there's no higher point either. I 'borrowed' this design from XTerra - they have such fitting stock. Thought it would work here but apparently didn't think hard enough.

Could you please answer few questions for me:

- our tap water is slightly hard - you get 1 mm scale in the cattle after half a year. I'm going to fill it with coolant mix afterward but there's no way to get rid of the flush water completely. Is this bad for the cooling system?

- you mentioned to do this on warm engine - is this to have thermostat open or for some other reason?

- my garden hose water has temp about 5C now, can this screw up something inside the engine when it gets there as the temp of the 'coolant' will suddenly drop by about 90C?

Thanks

 

You gonna have to explain what it is you are doing exactly - the tank (overflow?) cannot possibly get filled if your radcap is on and acting normal


1mm scale is bad for sure - but you want to flush the thing and clean/rid the system of all the gunk - if you don't want to use tap-water for a few minutes, and can afford de-ionized water, then sure go ahead and rather use that, but imo a few minutes on tap-water and some of that staying in the system once you fill it properly, is imo not going to be the end of the world.

Thermostat should ideally be open to ensure you see the actual circulation through the motor and eventually out to the cabin heater yes.

Using 5C tap-water to keep the rad full is no problem if you only want to see the amount of fluid going to the cabin - you need probably 1 minute to make any deductions based on rev range and then you switch off so chances are that the cold water you put into the top of the rad will not even reach the engine at all.

 

I'm not doing anything, it's just my observation - when coolant is at MIN mark while the car is cold it get to MAX when it reaches normal temp or sometime after that, I never thought it's the problem and didn't pay attention. If it is at MAX when cold it gets full at hot. I thought it was normal...

I used to live in place where you get that in less than 1 week . When you make a tea it got into reaction with water and became 'muddy' - you couldn't see through the glass anymore. Soap also didn't work, it actually did by reacting with water. Chem at work .

Thank you for the explanations, I'll take a look there over weekend and probably post the picture of how coolant looks like.

 

The coolant tank does not and should not show such a huge variation for normal engine operating temperature (not overheating) - if its level is at min when cold, then the expansion tank level will probably only go up by about 10mm with a 1Bar radcap ................. if even that.

Having said that - I still dont follow how you can make that earlier observation re the expansion tank level with the radcap in place, and then at the same time make the satement that you get nothing out of your "T" if you open it to atmosphere - imo if you open that T water is going to come out of there in a huge hurry if the motor is at normal operating temp because you will have around 10psi sitting behind that

 

I think, it actually makes sense - I don't have those 10 psi, the extra coolant is bled into expansion tank without much resistance. It would explain both variation in level and lack of pressure on T fitting end. My rad cap must be toast, I'll check it out, thanks for the sensible discussion/reference info.

 

Complete confusion then - you cannot possibly have a motor with no cooling issues if that is the case - if the radcap never reaches or maintains around 10psi at normal operating temp, then your coolant must be at boiling point just about permanently............. your extreme cold weather may be able to mask the sure disaster waiting to happen to a large extent though

Note that you will only have the about 10psi with a hot motor in the coolant as long as your T valve is closed and the radcap doesn't release any fluid - soon as you open the T valve the pressure will drop to close to 0 again


................and if your radcap is not keeping the coolant pressurized when at normal operating temp then its just about guaranteed that your coolant will have a lot of air in it - and THAT explains for sure why you have no/bad heat in the cabin

 

I just replaced the cap with another one from my 5 gen max and it indeed increased pressure in the system - water finally shot out of T fitting for about 30 cm high (in the clear hose connected to T). Hard to tell if it helped heating yet as I didn't drive it anywhere.

 

The fact that you have indeed identified not only a problem with your cooling system, but also the fact that your radcap now pressurizes the coolant properly (?) will not in itself help (even though its one of the requirements) - you will have to get the air out of that system before cabin heating will start working properly

 

I realize that. It's just all my previous attempts to bleed the system didn't get me anywhere - I always felt stupid when cautiously unscrewing the bleeding bolt I found nothing was coming out of the hole. There has never been a pressure from inside the engine and somehow I never really thought about it. Now there's pressure I tried to bleed it today and there was fountain of the coolant out of bleeding bolt hole. Heat much improved and it seems to be increasing as the car goes through heating/cooling periods. Coolant level in the tank stays steady as well. AC at +32 setting and +3 outside decreased blower speed to 2 sectors which is a good sign . Thank you for your efforts, it helped me a lot. I'll flush the system over weekend anyway to see if I can make coolant clear.

The reason my stock cap leaked was simple - the rubber seal became old and brittle and few small pieces were missing. It must be a common problem with these cars due to their age.

 

The celebration was short - due to increased pressure I've got serious radiator leak . I bought cap from dealer so the pressure rating must be stock. I already bought the radiator as well, planning to replace it tomorrow.