High pressure in cooling system

I have high pressure in cooling system, and I've read a lot of threads about it, and people are telling that it's blown head gasket. What's interesting that I have this problem after head gasket job.

When I try to squeeze coolant hose coming from head to the radiator it feels really hard. If I unscrew coolant tank cap, the pressure releases and hose feels soft again. I've already replaced coolant tank cap, radiator, thermostat, but nothing seems to help.

Recently I was at car service and asked mechanic what pressure should be in cooling system, he said it can be up to 29 psi. If that's true, maybe it's normal for that hose to be so hard.

So I want to know if pressure up to 29 psi in cooling system is okay, and if it's not, where should I look for problems?

The car is 1998 Passat 1.9 tdi 110hp.

Talk about the head gasket you replaced - what was done, and why? was there an external leak.

Windex said:

Talk about the head gasket you replaced - what was done, and why? was there an external leak.

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I had coolant loss and my brother told me that it's probably head gasket, didn't noticed any visible leaks, so I started removing head. I took it to the guy who resurfaces heads and he asked me if it's really head's fault because it looks good, I said I don't know, but since head was already removed, I did resurfaced it anyway.

After placing head back onto the engine, I still had coolant loss, but a lot lesser than before. Then after couple weeks, I was again in same situation where coolant loss was excessive and I found leaking heater core hose. Replaced it and everything seemed to be fine until again after like couple weeks radiator started leaking. Replaced radiator, and now I don't have any leaks, but high pressure in cooling system.

I was even thinking that radiator and heater core hose started leaking due to high pressure in cooling system.

I've had some hoses feel hard, but the pressure in the system actually be in spec or slightly over.

If I were to diagnose your car properly, I would test the coolant for the presence of hydrocarbons (test kit available through most parts supply houses), and I would also test the actual pressure in the system - one can fabricate a gauge fairly easy by drilling and tapping a spare reservoir cap to accept a 0-30psi gauge and testing the actual pressure in the system - hand on a hot hose is not very accurate.

The radiator cap should be rated at 22 PSI so "Jethro" the oil jockey may have been on crack that day telling you 29 PSI. The cap you bought should be the correct pressure rating. What is it's brand and part number?

Oh, and stop throwing parts at the problem. With your original complaint, you should have had the head pressure tested when it was resurfaced. The tell for head gasket or head leaks is bubbles in the coolant ball with the engine idling.

Windex said:

I've had some hoses feel hard, but the pressure in the system actually be in spec or slightly over.
If I were to diagnose your car properly, I would test the coolant for the presence of hydrocarbons (test kit available through most parts supply houses), and I would also test the actual pressure in the system - one can fabricate a gauge fairly easy by drilling and tapping a spare reservoir cap to accept a 0-30psi gauge and testing the actual pressure in the system - hand on a hot hose is not very accurate.

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I had same idea, since I have spare cap now I think I'll try this.

Ol'Rattler said:

The radiator cap should be rated at 22 PSI so "Jethro" the oil jockey may have been on crack that day telling you 29 PSI. The cap you bought should be the correct pressure rating. What is it's brand and part number?
Oh, and stop throwing parts at the problem. With your original complaint, you should have had the head pressure tested when it was resurfaced. The tell for head gasket or head leaks is bubbles in the coolant ball with the engine idling.

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I also thought that 29 psi is too much for cooling system, that's why I asked here about the pressure. The cap I bought is Topran 107532. I can't remember if there was any bubbles in the coolant tank, so I will take a look at it today.

Weird things happening... First of all, there was no bubbles in coolant tank while engine was idling, I even tried to rev a little bit, still no bubbles.

What was weird that I noticed if I open coolant tank cap and release the pressure, I'm not getting hot air inside the car anymore, even though temperature in climatronic is set to highest. If I rev engine up to 2k rpm, I'm getting hot air again, when I release the gas and let it idle, the air gets cooler and cooler.

When the pressure builds up in the cooling system then it doesn't matter if I'm idling or revving, I get hot air.

Another thing is that lower hose coming from water pump after thermostat to the radiator bottom is cold even though engine temperature is at 90c, is it supposed to be like that? Thermostat is replaced few days ago.

Are you sure the water pump is actually working? Sounds like a blockage somewhere or the pump impeller is not functioning.

aja8888 said:

Are you sure the water pump is actually working? Sounds like a blockage somewhere or the pump impeller is not functioning.

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I have replaced water pump a year ago, as I remember it had metal impeller, so I don't think it could fail so fast, but things happen. If I remember correctly, it's not that hard to remove water pump, I think should take a look at it.

My first thought when I noticed all those problems was that there's a blockage somewhere, but I'm not 100% sure, and if there is a blockage, I would still don't know how to find it.

I've been driving this car for a few months with only water in cooling system, instead of antifreeze. I've heard that water is bad for cooling system because it's corrosive. So maybe water actually damaged something in my cooling system, possibly water pump?

Btw if water pump would be damaged and/or not functioning, wouldn't my temperature raise above 90c? It's never been above 90c.

You never said how you were measuring the temperature. If you are relying on the dash gauge, then that is not enough. It is buffered to avoid showing large variations in temp that happen during normal driving to avoid having the customer complain to the dealer.

Get an OBD scanner and check the temp right from the sensor while you perform the tests you did previously. It could be a bad thermostat, a jammed thermostat (if you reused the housing, it has pins that could break off and lodge in the t-stat), etc.

So I checked the temperature via OBD, and I got some news. I always drive with climatronic temperature set to highest, thus coolant temperature was something around 87-93c. When I turned off climatronic, the temperature raised up to 105c and then I stopped the car, because I didn't knew what temp is dangerous for the engine. I was driving in 5 gear, rpms around 2k.

While idling temperature dropped to ~97c, then I checked hose coming from thermostat to the radiator, and unfortunately it was still cold... Then I unscrewed coolant tank cap, the temperature dropped to 93c and when I closed it again, temperature raised back to ~97c.

So basically if I drive without climatronic set to highest temp, the coolant temperature keeps raising, and with climatronic turned on and temp set to highest, it keeps around 87-93c.

Btw my thermostat flange does not have pins, I have seen ones with pins, but mine doesn't have them.

What is the outside temp?

owr084 said:

What is the outside temp?

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When I was checking coolant temperature it was something around 9c

Today I removed water pump, I was expecting to see broken propeller, but unfortunately, water pump was in perfect condition.

Now I have one more problem, heater won't blow hot air, and one of the heater core hoses is hot and another one is cold. Is it possible that my heater core is clogged, even though, couple weeks ago it was working perfectly?

These heater cores do have a tendency to clog up.

Many have had luck with flushing water through the core back and forth between the inlet and outlet, but others have tried that and had to replace anyway.

modee said:

Today I removed water pump, I was expecting to see broken propeller, but unfortunately, water pump was in perfect condition.

Now I have one more problem, heater won't blow hot air, and one of the heater core hoses is hot and another one is cold. Is it possible that my heater core is clogged, even though, couple weeks ago it was working perfectly?

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Did you bleed the coolant hose?

There is a bleed hole on of the cooling hoses going to the heater core. You pull the hose back a little to expose the hole, and let the air bleed out. The hole is shown with a white circle around it.

johnboy00 said:

Did you bleed the coolant hose?

There is a bleed hole on of the cooling hoses going to the heater core. You pull the hose back a little to expose the hole, and let the air bleed out. The hole is shown with a white circle around it.

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No I didn't. I will try to bleed it and if it doesn't help, I'll try to flush the heater core.

Bleeding didn't changed anything. Instead of flushing heater core, I just connected both heater core hoses together, and hoses were still hard and pressurized. So I guess there's only one thing left, that can cause this problem, it's the head gasket.

Is it possible that this problem happens because I used old head bolts, and didn't tightened the last step? I tightened them in 3 steps, 40Nm, 60Nm, 90°, but there's another fourth step that I forgot, it's again 90°.

modee said:

Bleeding didn't changed anything. Instead of flushing heater core, I just connected both heater core hoses together, and hoses were still hard and pressurized. So I guess there's only one thing left, that can cause this problem, it's the head gasket.

Is it possible that this problem happens because I used old head bolts, and didn't tightened the last step? I tightened them in 3 steps, 40Nm, 60Nm, 90°, but there's another fourth step that I forgot, it's again 90°.

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I'm 90% sure head bolts are TTY (torque to yield) and must be replaced. I think someone else will confirm that soon.

johnboy00 said:

I'm 90% sure head bolts are TTY (torque to yield) and must be replaced. I think someone else will confirm that soon.

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Yes I know they're TTY, and I've should replaced them, but I didn't thought it can cause any problems. Now I just want to know if that's the reason to my problem, not fully tightened and old bolts.

When head bolts are designed to be replaced and TTY, the reason is to ensure even and proper clamp load on the head.

Your head is not fully tight against the block, it stands to reason that the highest pressure would be the first to leak - combustion into the cooling system.

Buy new bolts and gasket.

Wash rinse & repeat.

Today I removed cylinder head, took it to the guy who resurfaces them, and he said there's nothing to resurface, it's still in perfect condition, since last resurface was done ~3 months ago.

So I cleaned cylinder head and engine block as well, sprayed head gasket with copper gasket sealant, bolted on head onto the engine block (this time, I used new bolts and tightened them to specification), and bolted on another things onto the engine/head.

When I tried to start the engine, I got a lot of smokes. It's not surprising, since I've been having a lot of white smoke at cold temperatures at idle. But another thing surprised me. The oil level dropped and when I crank the engine, oil light starts blinking. I checked oil level, and it was at the minimum, where it was at the maximum before head job. I filled it up a little bit and oil level didn't dropped again, but I'm still getting oil light blinking when cranking the engine. What's the problem now?

I know it's hard to start the engine after head job, so I didn't had time to start it today, I will try it again tomorrow, but since I'm having problems with oil now, I don't even know if it starts..

When the head gasket first blew, did it dump a large amount of coolant into the exhaust? I've had a few cars where I had to burn off the crap left inside. The worst was an S4 that had to burn off a few litres of oil That one smoked for a few days.

If the timing is set correctly and the fuel system bled and primed, it should not be all that hard to start the engine.

Uberhare said:

When the head gasket first blew, did it dump a large amount of coolant into the exhaust? I've had a few cars where I had to burn off the crap left inside. The worst was an S4 that had to burn off a few litres of oil That one smoked for a few days.

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My head gasket didn't blew, the head just wasn't tightened correctly.

Windex said:

If the timing is set correctly and the fuel system bled and primed, it should not be all that hard to start the engine.

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Timing is set correctly. I always bleed fuel system when the engine won't start. I turn injector lines nuts counter clockwise few turns and then crank the engine.

Fuel system is not primed, and I guess that's the reason why it's so hard to start the engine, because when I remove head I always remove fuel lines, so I can take off head easier, and there's always fuel dripping from one of the fuel outlets in injection pump.

Is there any way to prime the fuel system, without any special tools?

Assuming this is a VE engine with injector lines and a separate pump, also assuming you did not empty any fuel from the pump when you did the head...

If the pump has emptied bled of fuel, you will need to fill the pump first - pull a vacuum on the return line until you see fuel without any bubbles.

Then, connect all the injector lines and leave the 17mm nuts loose at the injectors - crank the engine over with rags underneath the loose nuts to catch the fuel. Crank the engine until fuel comes out of the lines on at least two injectors, then tighten the nuts again.

Engine should fire after that.

Windex said:

Assuming this is a VE engine with injector lines and a separate pump, also assuming you did not empty any fuel from the pump when you did the head...
If the pump has emptied bled of fuel, you will need to fill the pump first - pull a vacuum on the return line until you see fuel without any bubbles.
Then, connect all the injector lines and leave the 17mm nuts loose at the injectors - crank the engine over with rags underneath the loose nuts to catch the fuel. Crank the engine until fuel comes out of the lines on at least two injectors, then tighten the nuts again.
Engine should fire after that.

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I rechecked my timing, and injection pump was retarded by two teeths. So I put on timing belt again, this time correctly.

Instead of using vacuum pump, I sucked diesel with my mouth and engine fired up easily.

I drived my car for like 1 hour in a city, and heater core is working perfectly, cooling hoses are soft, no pressure in them. So far so good, so I guess that problem is solved.

Thank you very much to everyone for helping.

modee said:

I rechecked my timing, and injection pump was retarded by two teeths. So I put on timing belt again, this time correctly.

Instead of using vacuum pump, I sucked diesel with my mouth and engine fired up easily.

I drived my car for like 1 hour in a city, and heater core is working perfectly, cooling hoses are soft, no pressure in them. So far so good, so I guess that problem is solved.

Thank you very much to everyone for helping.

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Great to hear! Thanks for updating the thread.

aja8888 said:

Great to hear! Thanks for updating the thread.

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What was most weird, that not tightening to torque spe ification was causing all that problems. It was a horrible story, but it solved my problem, so I guess that my problem helps other ones as well..