928ntslow

I have narrowed this down to the pump or the water bridge, but maybe someone can throw some ideas out.

SYMPTOMS
- Engine warms up, but slowly. Will warm up in about 5-10 minutes according to
gauge reading.
-Heater on high, blows cold air
-Gauge will rise to upper red line and stay there
-Upper radiator hose is warm, but not hot, lower radiator hose is cool
-Rev engine a few times and heater suddenly blows hot air and gauge needle
comes down to normal.
-Radiator hoses then warm up
-Let it idle and after a few minutes, the same scenario happens.
-Same issue whether driving or idle.

COMPONENTS
-New thermostat and gasket properly installed
-Free flowing, non leaking radiator
-New expansion tank cap.
-No leaky hoses
-New heater control valve
-Pump condition unknown
-Water bridge shows calcification and some deterioration, but does not leak.
Flange at thermostat is flat and non corroded.
-New fan bearings and viscous fan in proper order
-Properly tightened utility belts as well as timing belt.

If there was blockage in the system, this same scenario wouldn't keep repeating. It is as if the thermostat doesn't open and then opens when engine is revved then closes again. Could this mean the water bridge is toast? Are there pin holes that should be clear in the water bridge? Not real sure how it flows in there, though I know it is mostly wide open...just not sure about by-passes or other passages.

Any ideas?

ZEUS+

When the tstat is closed coolant flows in the engine. When tstat opens it closes the rear passage and cooled coolant from rad flows through entire system. It does sound like a pump problem.

tomboyea123

I had the exact same symptoms on my murph stage 3 gts engine in my 89 gt.I put in a lower temp thermostate(75 degree) with the valve at the top.Then I changed another gasket about 3 inches under the thermostate. The original gasket looked sort of waterloged and swollen. Sinse then volia it runs between 165-175 degrees on the gadge

Tom. M

Could there be something that is keeping the thermostat from functioning..a small lip or something that when you rev it ...the extra pressure provided allows it to get past this?..Just a SWAG..something has to be opening the thermostat when you rev...

Later,
Tom

edit..just reread...does sound like the impeller is not spinning from time to time...better get in there and replace the pump..might as well do the whole front end WYAIT...
Good Luck..

perrys4

Keith is good at the whole front end thing. :-)

Mrmerlin

sorry but I am not sure what car your working on??
from what you say it sounds like an air pocket, and its low on coolant.
Does your water bridge have the famous rear thermo seal? If it does was it replaced, ?
What kind of new thermostate do you have ?
If you remove the small line from on top of the radiator while the engie is running and the resivour cap is removed does coolant come out of this?
Is the heater control valve correctly oriented?
Is it possible that the heater control valve isnt opening fully or it has a pinched line?

928ntslow

Thanks for the advice people. Sorry, but I should have mentioned a 1982 Euro 4.7L...my bad. Old style water bridge with no rear seal.

I should also mention that when I received the car, one of it's known issues told to me by the PO was the overheating. He said he yanked the old thermostat thinking this would fix it...he's a Ford guy. So when I got it, I changed out what I had mentioned in the previous post. I just hadn't gotten into the pump ....yet. Everything is installed properly as I had said. I will say it again, everything is installed properly. No air pockets, they would have most definitely worked themselves out by now anyway. You can see water movement in the expansion tank after warm up, so this tells me the pump is working. Heater control valve does not have anything to do with it overheating, just if the hot water gets to the core.

If you look in the water bridge, there is nothing there to stop the thermostat from opening. The important thing on the older cars is to seat the gasket and the thermostat...this has been done correctly.

This was a pre existing condition and I even changed out the radiator to see if that was the issue...it was not. Strange that it would be the pump...no abnormal sounds at any point during this process.

Has anybody an OB bridge they can look at to see if there are any small passages. I am thinking that when I rev and create more pressure, water is forced through one of these passages either relieving or creating pressure to flow past the thermostat. I think I can safely say at this point that the overheating is due to the flow not passing through the radiator based on my findings. I just have to figure out why and I know it is either the bridge or the pump. BUT, why would the pump work intermittently? Has anyone ever heard of this? If so, why was it doing that?

Remember, this is a recurring process while the engine is running. Not to be confused with every time I start it up. It will cycle through hot and cold as long as it is running. Revving seems to cause everything to cool back down immediately. You can watch the needle drop in less than 20 seconds.

Mrmerlin

Given the new info I would take a look at the pump impeller , you wont hear it grindiing away on your block, if thats the case,. the only other thing i could think to look at before you do the pump is to remove the cap on the resivour and see if bubbles are coming out of the resivour,while the engine warms up.
If you see bubbles then the head gasket or head or cylinder may have a crack.
It can also be possible for the either the impeller or the pump drive pulley to have a slip fit on the WP shaft, and be grabbing and then letting go

Dave H.

most likely the impeller. happens alot on VW/Audi's with the plastic impellers...

marton

When I had a problem (mine boiled up after about 10 minutes) I put a longer clear plastic tube between the motor and the heater control valve. Then I could see that the pump was not working. You need a longer tube so it has a mix of air & water then that makes it easy to see the flow.
Even at tick over you should get a good flow. Of course you need the heater turned on. In your case it sounds like the pump is working at least partially (otherwise it would boil up) so it will be harder to verify the problem.

Are you sure this is not simply due to engine vibrations?

The water pump is a slip fit on the TB (no cog with teeth) so a slack TB or a partially siezed WP bearing would give the same effect.

Forgot to say mine is also a 1982 Euro 4.7L; I have had it six years now and every year I get coolant leaks but never from the same place, still trying to track down the current one - about a cupful in 800 miles.

Marton

Mike Frye

There was a thread a little while ago started by John Veninger about an unusual water pump failure mode. AFAIK the only reported cases were in racing conditions, but since it was there when you got it...

The failure mode was that either:
a) The impeller actually spun on the shaft (more likely the shaft spun while the impeller didn't) or
b) The pulley spun on the shaft

In both cases the pulley and the impeller are only press fit on the shaft and can spin in extreme circumstances. Given that, once it spins once I think it is possible that it could spin more easily after that.

Although you're not in danger of bending up your valves with that MY, I would not crank it again until I got in there and replaced the TB/WP. It's part of the initial maintenance list when buying a car anyway, so why wait? I would expect to see partially seized bearings and/or a spun pulley or impeller.

IcemanG17

Keith
Are you sure its running hot?? If your really lucky the gauge is screwy.....check the temp of the coolant or at least the hoses-pump with an IR temp gun....

But it does sound like the impeller is not spinning properly

hupp

Check out Dan Perez's "Old Bugger Engine Coming Out" thread -- he has pics of an OB bridge from the front and rear posted.

Bill Ball

When was the water pump last replaced?

928ntslow

All very good questions.

I have no idea about the TB/WP. I pulled the cam sprockets to change out the cam seals. They looked good, the belt looked good and I tightened to spec. I just never got down to the WP. Wasn't a concern and a TB/WP job on these old cars is a snap, so I may just order a new pump and take the 5 minutes to change it out.

There IS flow through the expansion tank. I have seen coolant flow into the clear water after the thermo opens. I know the gauge is OK. I have also seen the red light come on when too hot and the expansion tank over flow with boiling water. No oil in water or water in oil, so head gaskets are OK.

I guess I always kinda answer my own questions. I just like to see if others are thinking what I am thinking. Looks like the next step IS to check the pump. Lets hope I find the problem.

Thanks fellers!